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1
Bridson, Jessica. "The effect of fishing on the evolution of North Sea Cod." Thesis, University of Strathclyde, 2001. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=9352.
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Nimick, Aileen Margaret. "Modelling Fishing Gear to Address "More than Minimal and Not Temporary" Fishing Effects to Essential Fish Habitat." Thesis, Alaska Pacific University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10845718.
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<p> The Magnuson-Stevens Fishery Conservation and Management Act (MSA; Magnuson-Stevens Fishery Conservation and Management Act. 2014. (16 U.S.C. 1801–1891(d)) mandates that fisheries management councils in the United States prevent adverse, or “more than minimal and not temporary”, fishing effects to essential fish habitat (EFH) to the extent practicable. Councils were left to decide what effects qualified as “minimal” and “temporary”. The lack of explicit definition in the MSA and its accompanying Final Rule has resulted in inconsistent habitat management throughout the country. The EFH mandate was written under an implicit assumption that councils have the scientific information necessary to effectively manage EFH. Basic information is lacking, such as what type of habitat occurs where, and how fishing effects habitat features. Chapter 1 briefly reviews the history of EFH regulation, the consequences of regulatory ambiguities and information gaps, and highlights that high latitude fisheries management can be disproportionately affected by climate variability. Thus, requiring investment in baseline habitat assessment and monitoring and renewed focus on under developed areas of research e.g. Fishing effects and gear-habitat interactions. </p><p> Councils have attempting to quantitatively describe fishing effects to EFH through the use of mathematical models. The most recent of which, the Fishing Effects (FE) Model, was used in the North Pacific Fisheries Management Council 2015 EFH Review cycle. The FE Model uses discrete time steps (monthly) and spatially explicit fishing effort and sediment data to calculate an estimated habitat disturbance. The FE Model is calculated in two-dimensions and implicitly assumes that if fishing gear does not contact the seabed, then there is no gear-habitat interaction. Some features stand taller than raised gear (e.g. sea whips, <i>Halipteris willemoesi</i>, in the North Pacific can up to 2m tall) and may interact with fishing gear. The FE Model in two-dimensions does not account for this potential interaction and cannot effectively simulate gear modifications. Chapter 2 proposes an adapted version of the FE Model that accounts for the vertical interactions through the use of discrete height bins. To accurately estimate interactions on and above the seabed, fishing gear has to be recharacterized. To demonstrate this the Bering Sea flatfish trawl was recharacterized by calculating how much of the nominal gear width is present in each height bin. A detailed methodology is provided to allow this method to be applied to any fishing gear. The adapted FE Model can be used to simulate gear modifications, as is shown by simulating two modifications of the flatfish trawl. This chapter will inform the 2020 EFH Review cycle as the FE Model is improved. </p><p>
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Modig, Karl Johan. "Selective fishing gear : A review on the effects of selective fishing gear on cod in the Baltic Sea." Thesis, Linnéuniversitetet, Institutionen för biologi och miljö (BOM), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-31302.
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The populations of Atlantic cod (Gadus morhua) in the Baltic Sea has been heavily exploited for decades, with fishing mortalities close to, and for several occasions, even above one. The larger part of the spawning stock biomass is consequently being removed each year. The issue of fisheries induced evolution (FIE) has been gaining attention from researchers lately. The selection pressure driving this evolution is powered by a connection between high mortality rates and heritable traits. The fishing in the Baltic Sea is mainly performed with size selective gear that can impose selection on traits like size-at-age or size-at-maturity. In this review I show how FIE may affect the Baltic cod towards decreased size-at-age/maturity and how size selective fishing on stocks at low levels can increase the inherent instability of the population as well as deprave the Baltic Sea of ecosystemic services from cod.
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Ricks, Benjamin Riddick Maceina Michael J. "The effects of tournament fishing on dispersal, population characteristics, and mortaltiy of black bass in Lake Martin, Alabama." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/master's/RICKS_BENJAMIN_26.pdf.
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Miller, Nathan. "The Gulf of Mexico Red Snapper Individual Fishing Quota Program: The Effects on the Fishing Industry and Potential Outlook." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3626.
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In January 2007, the Gulf of Mexico red snapper fishery took a step toward sustainability and began management under an individual fishing quota (IFQ) system. The hope is that direct ownership stakes by fishers brings more direct involvement on behalf of the boat owners and fishermen as well as more responsible and sustainable fishing practices on depressed fish populations. The research was conducted in order to study the welfare of local fishing communities as well as the effects on the red snapper fishery itself. Traditional fisheries and economic data were analyzed. In addition a Data Envelopment Analysis (DEA) of the Florida Gulf Coast communities involved in the red snapper fishery was performed to compare to the analysis of fishing communities prepared by the National Marine Fisheries Service (NMFS). Finally, online and phone surveys of fishermen involved in the red snapper fishery were performed to gauge their responses to the change in management.
The study reveals a strong correlation between the DEA analysis of fishing communities affected and the analysis performed by NMFS, and reinforces DEA as a method of determining involvement in a fishery. Additionally, the thesis indicates the
red snapper IFQ has performed as expected in some areas by its supporters – an average gulf-wide ex-vessel price per pound increase of 10% in just three years; elimination of the rush to fish due to guaranteed quota; and a shift in fleet composition as the number of share owners owning less than 2.00% have dwindled, and the number of shareholders possessing greater than 2.00% of the quota has increased gulf-wide by 50%. However, in other areas such as effort reduction and bycatch rates, the IFQ appears to have mixed results. A reported decline in effort is likely attributable to a reduction in the overall gulf-wide red snapper quota between 2007 and 2008 rather than the IFQ, and even NMFS doubts the bycatch data that are being reported by fishermen. Most importantly, current IFQ shareholders were surveyed via phone and internet revealing not only an overall disapproval by most fishers of the IFQ design process, but also effects contrary to those publicized by IFQ supporters, and a general distrust in fisheries management.
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Søvik, Siri Lise. "Characterisation of enzymatic activities in by-products from cod species : effect of species, season and fishing ground." Doctoral thesis, Norwegian University of Science and Technology, Department of Biotechnology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1267.
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Westera, Mark B. "The effect of recreational fishing on targeted fishes and trophic structure, in a coral reef marine park." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2003. https://ro.ecu.edu.au/theses/1499.
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Recreational line fishing is highly targeted at predatory fishes, making them vulnerable to overfishing. These same fishes play a role in trophic structure by regulating prey species. Despite increasing numbers of fishers, few studies have investigated the potential effects of recreational fishing on fish populations and subsequent trophic effects. This project investigated whether there were differences in fishes and benthos between unfished and recreationally fished areas, and whether the removal of targeted fishes influenced trophic structure. The study was conducted at the Ningaloo Marine Park, Western Australia, which had Sanctuary (no-take) and Recreation {recreationally fished) Zones. Data were collected from three regions (Mandu, Osprey and Maud) and replicated over time. Fish assemblages, benthos and trophic interactions were compared between zones at each region. At Ningaloo the lethrinids (emperors) are a top-order predatory fish and the preferred target of recreational anglers. The algal-grazing urchin Echinometra mathaei comprised 51% of macro invertebrate abundances and was heavily preyed upon by lethrinids, being recorded in 50% of the guts of sampled fish. In nil regions, Sanctuary Zones had a greater biomass of lethrinids than Recreation Zones, but there were no differences in non-targeted fishes between zones. Despite the consistent effect on lethrinids, there were inconsistencies among regions in the predator-prey relationships. At Mandu, Echinometra mathaei abundances were inversely related to lethrinid biomass, suggesting a strong predator-prey interaction. In the Recreation Zone, the abundances of E. mathaei were four times greater, and macro-algal cover was half, that of the Sanctuary Zone. Furthermore, algal composition differed between zones, and this was driven by fucoid brown algae, which dominated the diets of E. mathaei. This was interpreted as evidence of a trophic cascade resulting from the removal of lethrinids at the Recreation Zone. At Maud, different results were recorded. Abundances of Echinometro mathaei and lethrinids were both higher in the Sanctuary Zone, than the adjacent Recreation Zone. E. mathaei reside in the crevices of rock, dead coral or Echinapora coral, which provided refuge from predation and this habitat was more available in the Sanctuary Zone. It is suggested that the availability of this habitat confounded the effects of predation. Macro- algal cover was lower in the Sanctuary Zone indicating a grazing effect from E. mathaei. At Osprey there was higher cover of E. mathaei habitat in the Sanctuary than the Recreation Zone. However, there were no differences in macro-algal cover, which was consistent with a lack of difference in E. mathaei abundances. The effect of E. mathaei grazing was unlikely to have been confounded by fishes that graze macro-algae, as they did not differ between zones at any region. These results indicate that recreational fishing reduced fish populations below that of adjacent protected areas at Ningaloo Marine Park, and in one region this resulted in a trophic cascade. This may be the first study that has recorded evidence of a trophic cascade where recreational line fishing is the only means of extraction. However, the results also show that this is not a consistent response to reduced fishing pressure; in other regions, changes in predatory fish abundance did not result in differences in the abundances of their prey, suggesting no trophic cascade. The studies have contributed towards an understanding of fish-habitat interactions and provide a baseline for future monitoring of the Ningaloo Marine Park. They also have important implications for marine park managers in terms of defining their expectations when implementing Sanctuary Zones. The results also show that Sanctuary Zones have the potential to be effective tools for fisheries management.
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Costa, André Bento. ""Fishing on Alentejo rocky shores - intensity, yield and protection effects"." Master's thesis, Universidade de Évora, 2012. http://hdl.handle.net/10174/15861.
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Actividades de pesca são tradicionais em Portugal e, na costa sudoeste continental Portuguesa, os pescadores geralmente exploram zonas rochosas intertidais ou subtidais pouco profundas, capturando peixes teleósteos e diversos invertebrados marinhos. Desde 1995, que esta costa está parcialmente protegida por um parque natural (Parque Natural do Sudoeste Alentejano e Costa Vicentina - PNSACV). Uma série de medidas de gestão de pesca têm vindo a ser implementados desde 2006 e mais recentemente, foi adoptado um novo plano de ordenamento do parque natural, que acrescenta normas ainda mais restritivas. Este estudo tem como objectivo analisar a variação espacial e temporal da intensidade e do rendimento das actividades de pesca no litoral rochoso Alentejo e avaliar os efeitos das medidas de protecção implementadas a essas actividades. Foi também avaliada a opinião dos pescadores, sobre as leis de gestão de pesca existentes e foi caracterizada a sua actividade. Para a análise da intensidade de pesca foi utilizado o método de “roving creel survey”. O rendimento das actividades de pesca foi estimado através de entrevistas directas a pescadores e observações de 30 minutos a pescadores à linha. Informação relativa à opinião dos pescadores e caracterização das suas actividades foram obtidas através de inquéritos. O trabalho de campo decorreu entre Janeiro e Julho de 2012. A amostragem foi efectuada em seis áreas e estratificada por: tipo de dia (dias de semana, período semanal de interdição, fins-de-semana/feriados); áreas (fora do parque; dentro do parque); período de defeso do sargo (antes, durante, depois) e período da Páscoa (antes, durante, depois). Usando dados publicados anteriormente, foi realizada uma comparação interanual relativamente ao período da Páscoa entre os anos de 1995, 1996 e 2012 de forma a avaliar os efeitos das medidas de protecção. As principais actividades de pesca documentadas no litoral rochoso Alentejo foram a pesca à linha e o marisqueio. O valor médio global de intensidade para todas as actividades humanas foi de 1,32 utilizadores.km-1.dia-1. Foram registados valores globais superiores durante fins-de-semana e/ou feriados, especialmente em áreas fora do parque. Durante o período semanal de interdição as áreas do parque registaram
uma diminuição significativa no número de pescadores.km-1. No entanto, durante o defeso do sargo, a redução esperada no número pescadores à linha não foi observada em áreas protegidas. Foi observado elevados valores de intensidade e predação total durante o período da Páscoa, evidenciado em anos anteriores à implementação das medidas de protecção. A comparação interanual revelou uma variação da intensidade de pesca entre área e períodos para todas as actividades. Foi obtido um rendimento de cerca de 3 toneladas de pescado (peixes e mariscos), proporcionando um rendimento médio de 0.15 kg.h-1 por pescador. As áreas do parque apresentaram um rendimento superior relativo à predação total. O valor de rendimento obtido com as entrevistas directas, a pescadores à linha foi aproximadamente o dobro do valor obtido com as observações de 30 minutos. Os pescadores do litoral rochoso Alentejano são maioritariamente do sexo masculino com idades superiores a 30 anos, estão empregados no sector industrial ou são reformados/desempregados/estudantes, residem ou possuem naturalidade em concelhos com territórios abrangidos pelo parque natural, e capturam sobretudo peixes teleósteos e mariscos. A maioria conhece as leis portuguesas relativas à pesca recreativa e as medidas de protecção implementadas no parque. As medidas de protecção que afectam as suas actividades mais mencionadas pelos pescadores são: todas as medidas, período de defeso do sargo, e tamanhos e pesos mínimos do pescado. Em sentido contrário os pescadores que concordam com as medidas de protecção referem que as medidas mais acertadas são: todos os períodos de defeso, obrigatoriedade de licenças de pesca e tamanhos mínimos do pescado. Embora as medidas de protecção, recentemente estabelecidas no parque natural possam ter causado uma certa redução da intensidade de pesca, ainda é prematuro concluir sobre a totalidade dos efeitos de tais medidas. Como tal, para analisar e avaliar os efeitos precisos de medidas de protecção é indispensável uma constante monitorização das actividades de pesca; ABSTRACT:Fishing activities are traditional in Portugal and, in the Southwest continental coast, fishermen generally exploit intertidal or shallow subtidal rocky shores targeting shellfish and teleost fishes. Since 1995, the Portuguese SW continental coast is partially protected by a natural park (Southwest Alentejo and Vicentine Coast Natural Park - PNSACV). In this park, a series of fishing management measures has been implemented since 2006 and, more recently, a new management plan was adopted, adding more restrictive regulations. This study aims to analyse spatial and temporal variation of intensity and yield of fishing activities on Alentejo rocky shores and evaluate effects of protective measures implemented on these activities. The opinion of Alentejo rocky shores fishermen was evaluated on the existing fishing management laws and their fishing activity was characterized. Roving creel surveys were used for the analysis of fishing intensity. Fishing yield was estimated with direct inquiries and 30’ anglers’ observations. Information on fisheries characterization and fishermen opinion was obtained with direct inquiries. The field work took place between January and July of 2012. Sampling was made in six areas and was stratified by: day type (weekdays, banning period, weekends/holidays); park (areas outside and inside PNSACV park); sea bream closure season (before, during, after) and Easter period (before, during, after). Using previously published data, interannual comparisons between 1995, 1996 and 2012 Easter periods were performed to evaluate effects of protective measures on fishing intensity. The main fishing activities documented on Alentejo rocky shores, during the sampled period were shore angling and shellfish harvesting. Global mean value of intensity of all human activities was 1.32 users.km-1.day-1. Higher global mean values of users were registered during weekends/holidays, especially in areas outside the park. Park areas showed a significant decrease of fishermen.km-1 during banning period. However, during the sea bream closure season, an expected cutback in the number of shore anglers was not observed in the protected area. A high intensity of shellfish harvesting and total predation during Easter period were reported, matching the year’s prior protective measures. Interannual comparisons revealed variation among areas and periods regarding the intensity of all fishing activities. A total yield of fishing activities of about 3 tons of fish and shellfish was recorded, providing an average yield of 0.15 kg.h-1 per fisher. Areas inside the park presented a higher yield regarding total predation when compared with areas outside the park. The yield value of 0.21 kg.h−1 per angler, obtained with the inquiries doubled the yield value of 0.08 kg.h−1 per angler obtained with anglers’ observations. Alentejo rocky shores fishermen are mostly male, employed in manufacturing sectors or pensioners/unemployed/students above 30 years old, residents or with reported birthplace in municipalities with territory enclosed in the natural park and target mainly shellfish and teleost fish. The majority are aware of Portuguese recreational fishing laws and the protective measures implemented in the park. The most common protective measures referred by fishermen that affect their activity are: all measures, sea bream closure season and minimum size/weight of preys. In reverse, fishermen that agree with protective measures listed as more accurate measures closure (all seasons), mandatory fishing licenses and minimum prey sizes. Although recently established protection measures in park areas, might have caused some reduction in fishing intensity, it is still premature to assess the full effects of such measures. Therefore, in order to assess and evaluate accurate effects of protective measures a constantly monitoring of fishing activities should be implemented.
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Bracewell, Philip John. "The effects of electric fishing on some freshwater cyprinid fish species." Thesis, University of Hull, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327287.
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Leaf, Robert Thomas. "The Evolutionary Effects of Fishing: Implications for Stock Management and Rebuilding." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/28636.
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Recent empirical studies have demonstrated inter-generational morphological and life-history
changes in fish stocks that have been impacted by size-selective harvest. Evolutionary processes
in biological populations occur through differential survival and reproductive success based, in
part, upon individual phenotypic variability. Fishing is a source of directional selection resulting
in the directed removal of some phenotypes; however, many aspects of the evolutionary effects
of fishing remain have yet to be described. In order to better understand the life-history and
morphological changes that occur as a result of size-selective fishing, and their effect on fishery
dynamics, I first determined the suitability of Japanese medaka (Oryzias latipes) for selection
experiments. I performed selection experiments using Japanese medaka and report how
morphology and life-history characteristics changed over multiple generations of selection. I
then used these patterns of change in life-history and morphology to validate individual-based
simulation candidate models to test general mechanisms of life-history relationships. Finally, I
applied the individual-based simulation modeling approach in order to describe how biological
and fishery characteristics change in a large, age-structured population exposed to size-selective
fishing over multiple generations. I found that the Japanese medaka has attractive characteristics
for biological investigation. The selection experiments indicated large changes in the age-atmaturity,
including a nearly 50% decrease over four generations in the most intense sizeselective
removal regimes. However, I did not observe significant changes in length-at-age or
weight-at-age over the course of the experiment. Candidate simulation models were poor at
predicting some aspects of the life-history characteristics of Japanese medaka. The simulation
model to determine fishery characteristics predicted large decreases in yield and egg production
as a result of decreases in length-at-age. Understanding the relationships of life-history
characteristics and their role in determining population resilience is a step toward understanding
the importance of evolutionary processes in fishery management.<br>Ph. D.
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Coutin, Patrick C. "The effects of long term exploitation on tropical demersal fish stocks." Thesis, Coventry University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329574.
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Van, der Hoop Julie M. "Effects and added drag on cetaceans : fishing gear entanglement and external tag." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108892.
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Thesis: Ph. D., Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Biology; and the Woods Hole Oceanographic Institution), 2017.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 283-314).<br>Animal movement is motivated in part by energetic constraints, where fitness is maximized by minimizing energy consumption. The energetic cost of movement depends on the resistive forces acting on an animal; changes in this force balance can occur naturally or unnaturally. Fishing gear that entangles large whales adds drag, often altering energy balance to the point of terminal emaciation. An analog to this is drag from tags attached to cetaceans for research and monitoring. This thesis quantifies the effects of drag loading from these two scenarios on fine-scale movements, behaviors and energy consumption. I measured drag forces on fishing gear that entangled endangered North Atlantic right whales and combined these measurements with theoretical estimates of drag on whales' bodies. Entanglement in fishing gear increased drag forces by up to 3 fold. Bio-logging tags deployed on two entangled right whales recorded changes in the diving and fine-scale movement patterns of these whales in response to relative changes in drag and buoyancy from fishing gear and through disentanglement: some swimming patterns were consistently modulated in response. Disentanglement significantly altered dive behavior, and can affect thrust production. Changes in the force balance and swimming behaviors have implications for the survival of chronically entangled whales. I developed two bioenergetics approaches to estimate that chronic, lethal entanglements cost approximately the same amount as the cost of pregnancy and supporting a calf to near-weaning. I then developed a method to estimate drag, energy burden and survival of an entangled whale at detection. This application is essential for disentanglement response and protected species management. Experiments with tagged bottlenose dolphins suggest similar responses to added drag: I determined that instrumented animals slow down to avoid additional energetic costs associated with drag from small bio-logging tags, and incrementally decrease swim speed as drag increases. Metabolic impacts are measurable when speed is constrained. I measured the drag forces on these tags and developed guidelines depending on the relative size of instruments to study-species. Together, these studies quantify the magnitude of added drag in complementary systems, and demonstrate how animals alter their movement to navigate changes in their energy landscape associated with increased drag.<br>by Julie M. van der Hoop.<br>Ph. D.
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Stanovick, John Stuart. "Sampling characteristics of the bus route survey technique in the James River, Virginia." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/38651.
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Pilling, Graham Michael. "The effects of fishing on the growth and assessment of snappers and emperors." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314276.
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Maluleke, Vutlhari Absalom. "The effects of boat mooring systems on squid egg beds during squid fishing." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2528.
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Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2017.<br>In South Africa, squid fishing vessels need to find and then anchor above benthic squid egg beds to effect viable catches. However, waves acting on the vessel produce a dynamic response on the anchor line. These oscillatory motions produce impact forces of the chain striking the seabed. It is hypothesised that this causes damage to the squid egg bed beneath the vessels. Different mooring systems may cause more or less damage and this is what is investigated in this research. The effect of vessel mooring lines impact on the seabed during squid fishing is investigated using a specialised hydrodynamic tool commercial package ANSYS AQWA models.
This study analysed the single-point versus the two-point mooring system’s impact on the seabed. The ANSYS AQWA models were developed for both mooring systems under the influence of the wave and current loads using the 14 and 22 m vessels anchored with various chain sizes. The effect of various wave conditions was investigated as well as the analysis of three mooring line configurations.
The mooring chain contact pressure on the seabed is investigated beyond what is output from ANSYS AQWA using ABAQUS finite element analysis. The real-world velocity of the mooring chain underwater was obtained using video analysis. The ABAQUS model was built by varying chain sizes at different impact velocities. The impact pressure and force due to this velocity was related to mooring line impact velocity on the seabed in ANSYS AQWA.
Results show the maximum impact pressure of 191 MPa when the 20 mm diameter chain impacts the seabed at the velocity of 8 m/s from video analysis. It was found that the mooring chain impact pressure on the seabed increased with an increase in the velocity of impact and chain size.
The ANSYS AQWA impact pressure on the seabed was found to be 170.86 MPa at the impact velocity of 6.4 m/s. The two-point mooring system was found to double the seabed mooring chain contact length compared to the single-point mooring system. Both mooring systems showed that the 14 m vessel mooring line causes the least seabed footprint compared to the 22 m vessel.
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Tonello, Junior Antonio José <1976>. "Effects pinger use on dolphins' behavior and fish capture in artisanal fishing activities." Doctoral thesis, Università Ca' Foscari Venezia, 2008. http://hdl.handle.net/10579/778.
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Morrell, Thomas J. "Analysis of "Observer Effect" in Logbook Reporting Accuracy for U.S. Pelagic Longline Fishing Vessels in the Atlantic and Gulf of Mexico." Thesis, NSUWorks, 2019. https://nsuworks.nova.edu/occ_stuetd/511.
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Commercial pelagic longline fishers within the U.S. Atlantic, Gulf of Mexico, and Caribbean are required to report all fishing interactions per each gear deployment to NOAA’s Vessel Logbook Program of the Southeast Fisheries Science Center to quantify bycatch, increase conservation efforts, and avoid jeopardizing the existence of vulnerable species listed under the Endangered Species Act (ESA). To provide additional accuracy, the Pelagic Observer Program (POP) of the SEFSC deploys professionally trained observers on longline vessels to produce a statistically reliable subset of longline fisheries data. A comparison of self-reported (“unobserved”) datasets versus observer-collected (“observed”) datasets showed a general consistency for most target species but non-reporting or under-reporting for a number of bycatch species and “lesser-valued” target species. These discrepancies between catch compositions and abundancies regarding targeted species, species of bycatch concern, and species of minimum economic value can provide insight into increased fisheries regulations, stricter requirements, or additional observer coverage.
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Fitwi, Biniam Samuel. "Determination of salinity tolerance limits of tilapia, Oreochromis mossambicus, for use in tuna line fishery." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53355.
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Assignment (MPhil)--Stellenbosch University, 2003.<br>ENGLISH ABSTRACT: Many species of tilapia such as Oreochromis mossambicus are
euryhaline, able to adapt to different salinity waters. Their ability to
withstand high salinity levels has given rise to the possibility of using
tilapia as baitfish for tuna line fishery. The purpose of the study was to
determine the survival rate of tilapia O. mossambicus during direct
transfer from freshwater to the salinity levels of 0, 15, 20, 22.5, 25, 27.5,
30, 32.5, and 35 ppt. The data was analysed through means of
univariate ANOVAand regression analysis.
O. mossambicus showed no mortality to all salinity regimes up to
25 ppt. Mortality was observed at 27.5 ppt, with 100% mortality at 35
ppt. LC 50 and LC 90 were found to be 30.5 and 34.2 ppt, respectively.
The results indicate that tilapia (0. mossambicus) will survive a direct
transfer to salinities up to 25 ppt. acclimation will be required in the
event of transfer to salinity levels above 25 ppt, in order to prevent
significant levels of mortalities.<br>AFRIKAANSE OPSOMMING: Meeste van die tilapia spesies soos Oreochremis mossambicus het die
vermoë om by water van verskillende soutgehaltes aantepas. Dit is
hierdie vermoë om hoë sout vlakke te weerstaan wat die moontlikheid vir
gebruik as lewende aas in die tuna langlyn visvangbedryf moontlik maak.
Die doel van hierdie studie was om die oorlewingsvlak van tilapia, O.
mossambicus te bepaal by die oorplasing van varswater direk na
soutwater by vlakke van 0, 15, 20, 22.5, 25, 27.5, 30, 32.5, en 35 dele
per duisend. Die data is verwerk deur gebruik te maak van eenvariant
ANOVAen regressie analises.
O. mossambicus het geen mortaliteite tot gevolg gehad by al
die oorplasings van vlakke tot en met 25 dele per duisend sout nie.
Mortaliteite is wel gevind vanaf 27.5 dele per duisend, met 100 %
mortaliteite by 35 dele per duisend. LC 50 en LC90 was gewees 30.5 en
34.2 dele per duisend onderskeidelik. Die resultate toon aan dat tilapia
(0. mossambicus) sal oorleef by direkte oorplasing na soutwater by
vlakke van tot en met 25 dele per duisend. Tilapia wat na hoër vlakke as
25 dele per duisend oorgeplaas wil word, sal eers geleidelik moet
akklimatiseer om mortaliteite te beperk.
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O'Leary, Jennifer K. "Effects of fishing and trophic interactions on tropical reef builders : coralline, algae, and corals /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.
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Hlavacs, Lauri A. "Mapping the Effects of Blast and Chemical Fishing in the Sabalana Archipelago, South Sulawesi, Indonesia, 1991-2006." Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1219347860.
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Fernandez, John. "Analysis of increases in fishing power in the western rock lobster (Panulirus cygnus) fishery." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 1999. https://ro.ecu.edu.au/theses/1227.
Full textAbstract:
The western rock lobster, Panulirus cygnus, fishery represents a significant commercial asset to Western Australia, and it is therefore important that appropriate strategies are developed to effectively manage it. Because the fishery has a very high level of exploitation, researchers and managers rely significantly on annual stock assessments which are based on catch and effort data. This study will identify and assess the effects that changes in fishing power factors (e.g. advances in fish-finding technology) have had on estimates of catch and effort. The fishing power increases can be used to adjust nominal fishing effort to produce a time series of standardised effort which can then be used to reassess stock abundance measures, particularly of the breeding stock. The study will utilise the theory and techniques of regression and generalised linear modelling. A comparison of the normal and gamma distributions as the specified probability distribution in the model will be made .
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Williamson, Craig W. "Tournament-associated mortality and the effects of culling in Wisconsin black bass (Micropterus spp.) tournaments /." Link to full text, 2007. http://epapers.uwsp.edu/thesis/2007/williamson.pdf.
Full textAbstract:
Thesis (M.S.)--University of Wisconsin--Stevens Point, 2007.<br>Submitted in partial fulfillment of the requirements of the degree Master of Science in Natural Resources, College of Natural Resources. Includes bibliographical references (leaves 75-81).
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Bellinger, Nathan H. 1982. "Globalization and neoliberalism in Ecuador: The expansion and effects of the commercial tuna fishing industry." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11268.
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xi, 129 p. : col. ill.<br>Between the 1980s and early 2000s, Ecuador's commercial tuna fishing industry evolved from an insignificant player in the global marketplace to the third largest tuna fishery in the world. The reasons behind this dramatic expansion are integrally linked to economic globalization and more specifically, the proliferation of neoliberal economic policies throughout Latin America and Ecuador. In this thesis, I link neoliberal reforms, such as increased capital mobility, free trade agreements, and export-led development, to the rapid growth of Ecuador's tuna fishery, centrally located in Manta. I then explore the place-based effects of these reforms by elucidating the social and environmental impacts of the tuna industry. I argue that while there have been some benefits, such as economic growth and job creation, expansion of Manta's tuna fishery has exacerbated local inequalities, created serious environmental problems, and led to new workplace challenges for employees in the industry.<br>Committee in charge: Dr. Derrick Hindery, Chairperson;
Dr. Lise Nelson, Member
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Viegas, Vera Lúcia Coelho. "Pesca comercial na costa alentejana: rendimento, esforço de pesca, rejeições e efeitos da proteção." Master's thesis, Universidade de Évora, 2013. http://hdl.handle.net/10174/13081.
Full textAbstract:
Na área marinha do Parque Natural do Sudoeste Alentejano e Costa Vicentina, em 2011, foram criadas áreas de proteção que interditam totalmente ou parcialmente a pesca. Na restante área do PNSACV a pesca é regular e intensamente exercida, sendo uma das principais atividades económicas da região.
Por forma a avaliar o esforço de pesca, as capturas e rejeições, exercido dentro do PNSACV, foram realizados 57 embarques em embarcações de pesca comercial com diferentes métiers.
Determinou-se que a frota a operar na área de estudo, tenha em média 236 dias de faina por ano, sendo o métier Armadilhas o mais utilizado.
De entre os 4 métiers utilizados as Armadilhas foi o que retirou maior valor de biomassa anual, e o métier Cerco foi o que retirou maior número de indivíduos. As capturas apresentaram valores mais elevados no verão marítimo, e as espécies mais capturadas foram a sardinha, cavala e o polvo; Abstract:
“Commercial fishing on Alentejo coast: yield, fishing effort, discards & protection effects”
In the marine area of South-West Alentejo and Costa Viventina Natural Park were created in 2011, protected areas forbidding fishing totally or partially. In the remaining area of PNSACV fishing is exercised regularly and intensely, being one of the main economic activities of the region.
To assess the fishing effort, catches and discards, exercised within the PNSACV, 57 shipments were made on commercial fishing vessels with different métiers.
It was determined that the fleet operating in the study area, has on average 236 days per year of toil, being Traps the most widely used metier followed by Nets.
Among the 4 métiers used, Traps removed greatest annual biomass, and Siege métier was what pulled largest number of individuals. Catches showed higher values of biomass and in numbers in the maritime summer. The most captured species were sardine, mackerel and octopus.
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Samaranayaka, Ari, and n/a. "Environmental stochasticity and density dependence in animal population models." University of Otago. Department of Mathematics & Statistics, 2006. http://adt.otago.ac.nz./public/adt-NZDU20060907.114616.
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Biological management of populations plays an indispensable role in all areas of population biology. In deciding between possible management options, one of the most important pieces of information required by population managers is the likely population status under possible management actions. Population dynamic models are the basic tool used in deriving this information. These models elucidate the complex processes underlying the population dynamics, and address the possible consequences/merits of management actions. These models are needed to guide the population towards desired/chosen management goals, and therefore allow managers to make informed decisions between alternative management actions.
The reliability that can be placed on inferences drawn from a model about the fate of a population is undoubtedly dependent on how realistically the model represents the dynamic process of the population. The realistic representation of population characteristics in models has proved to be somewhat of a thorn in the side of population biologists. This thesis focuses in particular on ways to represent environmental stochasticity and density dependence in population models.
Various approaches that are used in building environmental stochasticity into population models are reviewed. The most common approach represents the environmental variation by changes to demographic parameters that are assumed to follow a simple statistical distribution. For this purpose, a distribution is often selected on the basis of expert opinion, previous practice, and convenience. This thesis assesses the effect of this subjective choice of distribution on the model predictions, and develops some objective criteria for that selection based on ecological and statistical acceptability. The more commonly used distributions are compared as to their suitability, and some recommendations are made.
Density dependence is usually represented in population models by specifying one or more of the vital rates as a function of population density. For a number of reasons, a population-specific function cannot usually be selected based on data. The thesis develops some ecologically-motivated criteria for identifying possible function(s) that could be used for a given population by matching functional properties to population characteristics when they are known. It also identifies a series of properties that should be present in a general function which could be suitable for modelling a population when relevant population characteristics are unknown. The suitability of functions that are commonly chosen for such purposes is assessed on this basis.
I also evaluate the effect of the choice of a function on the resulting population trajectories. The case where the density dependence of one demographic rate is influenced by the density dependence of another is considered in some detail, as in some situations it can be modelled with little information in a relatively function-insensitive way.
The findings of this research will help in embedding characteristics of animal populations into population dynamics models more realistically. Even though the findings are presented in the context of slow-growing long-lived animal populations, they are more generally applicable in all areas of biological management.
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Hsieh, Chih-hao. "Separating environmental effects from fishing impacts on the dynamics of fish populations of the Southern California region." Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3210008.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2006.<br>Title from first page of PDF file (viewed June 5, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Armstrong, Bryan. "Oceanographic Effects on the Behavior of Shallow-Set Pelagic Longline Fishing Gear in the Western North Atlantic." NSUWorks, 2009. http://nsuworks.nova.edu/occ_stuetd/246.
Full textAbstract:
The pelagic longline is a common gear type used worldwide primarily for the commercial harvest of swordfish (Xiphias gladius) and various species of tuna (Thunnus spp.). Different species are targeted by deploying the longline gear at different depths. This technique is effective because the probability that a fish will consume a bait is proportional to the amount of time that particular bait spends in the fish’s feeding habitat. The depth of the gear can be altered by changing the number of hooks per basket, with the gear being shallower with fewer hooks. Shallow longline sets are typically used when targeting swordfish and yellowfin tuna (Thunnus albacares), and may utilize four to six hooks per basket. The average maximum shallow-set gear depth is about 120 meters, but there is often variation in the depth range of the set because there are other forces acting on the longline gear than just gravity and buoyancy. Wind speed and direction, vertical current shear, fish captured by the gear along the line, and occasional interactions with other ships are all factors that can have a major impact on the depth of hooks during a set. To determine which factors have the largest impact on the depth range of pelagic longline gear, small temperature-depth recorders (TDRs) were deployed over two fishing seasons for a total of 70 longline sets. These sets were deployed in several different geographical areas within the Western North Atlantic. Depth profiles for several hooks per set were obtained and compared with the predicted depths. Observed hook depths were significantly shallower than the predicted depths in over 90% of cases. On average, the observed hook depth reached only 41% of its predicted value. These differences are compared between different regions and oceanographic conditions to assess if location or sea-surface state has a significant impact on the depth of longline gear. Wind speed was found to have a significant impact on the depth of longline gear, as well as wave height. The speed at which the gear moves through the water, how the gear was set with respect to current, and the geographical location of the gear also had significant effects on the mean settled depth of hooks within a set. The differences in gear depths between geographic locations were most likely caused by a combination of local environmental variations and setting technique.
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Ghebrehiwet, Dawit Yemane. "Assessing the effects of fishing on fish communities using South African case studies : empirical and theoretical approaches." Doctoral thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/8919.
Full textAbstract:
Includes bibliographical references (p. 207-227)<br>Currently heavy fishing is recognized as one of the major threats to the structural and functional organization of marine ecosystems in many coastal nations. The threat is mainly the result of the inherent nature of the various fishing activities: size selectivity, habitat destruction, biomass removal, and uncertainty in resource status and management of the resource. Thus this thesis investigates structural changes that result from fishing. This thesis aims to answer whether there were changes in the structure of fish communities off the of South Africa using two case studies, to explore the response of fish communities to the proposed creation of Marine Protected Areas and to investigate the alternate application of spatially uniform and heterogeneous fishing mortalities. The research questions of the thesis are answered through empirical analysis of landing data for the line fishery and analysis of demersal trawl survey data from the south coast of South Africa, and analysis of output of the Individual Based Model OSMOSE applied to the southern Benguela. Structural changes in the landings from the line fishery and south coast survey data are assessed using a variety of ecosystem indicators believed to capture such changes: size-based indicators {mean size, slope and height of the size spectra, mean Lmax7, proportion of size classes), species-based indicators (ordination by multidimensional scaling, and dendrograms, various diversity indices, dominance curves). Inferences are based on the reference directions of the indicators, according to the expected response of indicators to heavy fishing. Structural changes in the fish communities are observed, over the spatial and temporal bounds of the two case studies, to be the most likely cause of the observed changes is heavy fishing, although the influence of environmental factors cannot he ruled out. investigation of alternative implementation fishing mortality using the simulation model OSMOSE showed that the system and species biomass do differ between the two implementations, but the variability in the system remains the same. The modelled response of fish communities to the introduction of Marine Protected Areas is an overall increase in relative biomass of large predatory fishes and a decline in the biomass of prey and competitor species.
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Brown, Rachel L. "Untangling the effects of fishing effort and environmental variables on benthic communities of commercially fished scallop grounds." Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/4657/.
Full textAbstract:
The Isle of Man fishing industry is currently predominated by two lucrative and heavily exploited scallop fisheries, targeting Pecten maximus and Aequipecten opercularis. The impacts of which have previously been investigated, however without the addition of environmental information. This thesis represents a unique long-term investigation into the impacts of fishing pressure and environmental variables on the benthic invertebrate communities of fishing grounds found around the Isle of Man. A significant positive trend in seawater temperature was found, along with an inverse correlation with chlorophyll-α. Fishing pressure was found to have a small, significant negative effect on indices of diversity; however environmental variables were unable to explain the remaining patterns in diversity. The composition of each of the benthic communities was then investigated in more detail. Fishing pressure had a significant negative effect on densities of benthic invertebrates at some grounds; however this study showed that many of the heavily fished sites were composed of dredge-tolerant species. Significant relationships were found between the densities of Asterias rubens and Porania pulvillus and several environmental variables on the south-west fishing grounds, suggesting that environmental variation, rather than fishing pressure was responsible for variations in these species. Further evidence was found of the negative impact of scallop dredging from the long-term analysis of a closed area, implemented in 1989. Recovery of P. maximus has occurred within this closure, without the concurrent increase in of the predatory starfish A.rubens. Relationships between several benthic species with the closed area and environmental variables were found. However, the results of this study indicate a complex ecosystem, which is also affected by predator-prey interactions. The overall findings of this research indicate that closed area management is a relatively straightforward and effective measure in this region. Future management decisions will however, have to account for the potential effects of climate change.
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TULONE, Antonio. "ITALIAN COASTAL COMMUNITIES’ WILLINGNESS TO PAY FOR THE MITIGATION OF CLIMATE CHANGE EFFECTS ON THE FISHING INDUSTRY." Doctoral thesis, Università degli Studi di Palermo, 2020. http://hdl.handle.net/10447/395414.
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Telfer, Carli. "The Western Australian charter boat industry: Working towards long-term sustainability." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2010. https://ro.ecu.edu.au/theses/154.
Full textAbstract:
Fisheries agencies and industry are accountable for sustainable fishing practises from all sectors. Throughout Australia, commercial and recreational sectors have been the focus of monitoring programmes and management, yet charter boat industries have been providing a service to fee-paying recreational clients for decades and only recently have the industry become part of those monitoring and management programs. Charter boat industries exhibit characteristics of both commercial and recreational fishing sectors, charter operators are paid for a service and managed under a licensing framework, but their clients adhere to a set of recreational fishing regulations. Unlike the other two sectors, limited catch, effort and socio-economic data exist for the charter boat industry, although more catch and effort data has been collected from the Western Australian charter boat industry since late 2001. The main objective of this study was to assess the spatial and temporal trends in catch, effort and species composition of the Western Australia charter boat industry between 2002/03 and 2007/08 and develop an understanding of the social and economic framework of the industry and its clientele to identify potential implications for management and the future direction of the industry.
This thesis provides the first comprehensive examination of the charter industry in Western Australia and provides important information about the ecological, economic, social and governance perspectives. While this thesis attempted to cover all of these areas, it could not cover all in detail. It is essential that the charter boat industry of Western Australia is continually monitored, as it provides quantitative information that may assist in ensuring the long-term sustainability of the industry and fish stocks.
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Maufroy, Alexandra. "Drifting Fish Aggregating Devices of the Atlantic and Indian Oceans : modalities of use, fishing efficiency and potential management." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT150/document.
Full textAbstract:
Depuis le milieu des années 1990, l’utilisation de Dispositifs de Concentration de Poissons (DCP), des objets artificiels spécifiquement mis à l’eau pour agréger des bancs de poissons, est devenue de plus en plus importante pour la pêche au thon tropical à la senne. Cette utilisation massive des DCP, qui s’accompagne d’une utilisation massive de dispositifs de suivi comme les balises GPS et les balises échosondeurs, est aujourd’hui source d’inquiétude pour les stocks de thons, les prises accessoires mais aussi pour le fonctionnement des écosystèmes pélagiques. Cependant, les modalités d’utilisation des DCP et des balises GPS qui servent à les suivre restent mal connues, ce qui complique considérablement l’évaluation et la gestion des impacts de ces pratiques de pêche. Afin d’améliorer les connaissances actuelles de la pêcherie, les positions des balises GPS utilisées par les 3 armements français dans les océans Atlantique et Indien, constituant une part significative des DCP utilisés dans ces deux océans, ont été analysées. Ces données ont été combinées avec des multiples sources d’information : les livres de bord, les trajectoires VMS des senneurs français ainsi que des entretiens avec les patrons français. Elles nous permettent de mieux comprendre les stratégies de mise à l’eau des DCP et des balises, d’estimer le nombre d’objets flottants utilisés par les flottes de senneurs dans les océans Atlantique et Indien, de mesurer la contribution des DCP et des navires auxiliaires à l’efficacité de pêche des senneurs, d’identifier des destructions potentielles d’habitats par les DCP échoués and pour finir de proposer des solutions de gestion pour la pêcherie. Les résultats montrent une grande saisonnalité dans les mises à l’eau des deux océans, une croissance rapide du nombre de balises GPS au cours des 7 dernières années puisqu’elle est multipliée par 4.2 dans l’Océan Indien et 7 dans l’Océan Atlantique, des dommages possibles causés à des écosystèmes côtiers fragiles avec une probabilité d’échouage de l’ordre de 10% et finalement une augmentation de l’efficacité de pêche entre 2003 et 2014 de l’ordre de 3.8-18.8% dans l’Océan Atlantique et 10.7%-26.3% dans l’Océan Indien. Les entretiens avec les capitaines des senneurs soulignent la nécessité d’une gestion plus efficace de la pêcherie, avec entre autres l’instauration de quotas, une régulation de la capacité de la flotte de senneurs et un meilleur suivi des navires auxiliaires. Les résultats obtenus constituent les premières étapes nécessaires à une meilleure gestion de la pêche sous objet flottant<br>Since the mid 1990s, the use of drifting Fish Aggregating Devices (dFADs) by purse seiners, artificial objects specifically designed to aggregate fish, has become an important mean of catching tropical tunas. In recent years, the massive deployments of dFADs, as well as the massive use of tracking devices on dFADs and natural floating objects, such as GPS buoys, have raised serious concerns for tropical tuna stocks, bycatch species and pelagic ecosystem functioning. Despite these concerns, relatively little is known about the modalities of GPS buoy tracked objects use, making it difficult to assess and manage of the impacts of this fishing practice. To fill these knowledge gaps, we have analyzed GPS buoy tracks provided by the three French fishing companies operating in the Atlantic and the Indian Oceans, representing a large proportion of the floating objects monitored by the French fleet. These data were combined with multiple sources of information: logbook data, Vessel Monitoring System (VMS) tracks of French purse seiners, information on support vessels and Local Ecological Knowledge (LEK) of purse seine skippers to describe GPS buoy deployment strategies, estimate the total number of GPS buoy equipped dFADs used in the Atlantic and Indian Oceans, measure the contribution of strategies with FOBs and support vessels to the fishing efficiency of tropical tuna purse seiners, identify potential damages caused by lost dFADs and finally to propose management options for tropical tuna purse seine FOB fisheries. Results indicate clear seasonal patterns of GPS buoy deployment in the two oceans, a rapid expansion in the use of dFADs over the last 7 years with an increase of 4.2 times in the Indian Ocean and 7.0 times in the Atlantic Ocean, possible damages to fragile coastal ecosystems with 10% of GPS buoy tracks ending with a beaching event and an increased efficiency of tropical tuna purse seine fleets from 3.9% to 18.8% in the Atlantic Ocean over 2003-2014 and from 10.7% to 26.3% in the Indian Ocean. Interviews with purse seine skippers underlined the need for a more efficient management of the fishery, including the implementation of catch quotas, a limitation of the capacity of purse seine fleets and a regulation of the use of support vessels. These results represent a first step towards better assessment and management of purse seine FOB fisheries
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Nenadovic, Mateja. "The Effects of Bottom-Tending Mobile Fishing Gear and Fiber-Optic Cable Burial on Soft-Sediment Benthic Community Structure." Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/NenadovicM2009a.pdf.
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Schroeder, Robert E. "The ecology of patch reef fishes in a subtropical Pacific atoll: recruitment variability, community structure and effects of fishing predators." Thesis, University of Hawaii at Manoa, 1989. http://hdl.handle.net/10125/18158.
Full textAbstract:
The ecology of patch reef fishes was studied to quantify the main
factors that affect the natural variability of the fish community and
to determine the effects produced on the community by experimental
removal of predators. Initially, a year-long baseline description was
completed of the physical, biological and ecological characteristics of
8 pristine patch reefs at Midway lagoon. For over 3 subsequent years,
piscivorous predators were spearfished at least monthly, often for days
at a time, on 4 of the 8 reefs. Fish populations were visually
censused throughout the experiment. In all seasons and years of the
project, daily recruitment rate of postlarval fishes to natural patch
reefs was compared to that measured on standardized, artificial reefs
of various sizes and degrees of inter-reef isolation. Finally, all
baseline measurements were replicated and complete collections were
made of all fishes, to validate the visual census method.
Visual censusing was found to be of adequate precision and accuracy
for most resident, non-cryptic species (highest for small patch reefs).
Fishes could be assigned to size classes underwater by visual estimate
with high accuracy. Rotenone collections were highly effective in
quantifying many species commonly missed or underestimated in visual
censuses.
Only a few species composed the bulk of all recruits, while most
species were rare or not seen at all. Variation between species was
related to life history strategies or behavioral requirements. High temporal variability was found at the following scales: 1) Annuallywhere
variability increased with the magnitude of recruitment, and
different species recruited heavily in different years, suggesting that
species specific factors in the plankton are more important than
general oceanographic conditions; 2) Seasonally- pulsing strongly in
summer, and occasionally late fall, when favorable environmental
conditions may maximize growth and survival; and 3) Daily- with 1 or 2
strong peaks (each only a few days long) over a period of several weeks
of low, variable recruitment.
Small-scale spatial variability between replicate attractors
(standardized artificial reefs) and between attractor types (coral and
wire) were both high for a few species recruiting abundantly, although
most recruits are probably substrate generalists. Rigorous visual fish
censuses can adequately document moderate- to long-term temporal
variation in the abundances of recently recruited juveniles on patch
reefs (i.e., based on similar temporal patterns assessed by daily
attractors). Daily total recruitment rate increased, although at
diminishing densities, with (attractor) reef size, and with degree of
inter-reef isolation. Abundances of recently recruited fish censused
on neighboring, natural patch reefs (much larger than attractors)
increased with reef size. The effect of isolation on these natural
reefs was confounded by the stronger effect of reef size. These
results suggest that if optimum size and spacing of reefs is provided,
either by proper design of artificial reefs or selection of marine reserves, managers may enhance fish recruitment and ultimately improve
local fisheries:
Of the 135 fishes censused on the patch reefs studied, only 6
species together accounted for 70% of the total number of all fish,
mainly due to heavy seasonal recruitment pulses. Strong seasonal and
annual variability in recruitment was responsible for most of the
temporal variation in fish abundance. The structure of patch reef fish
communities at Midway was characterized by high unpredictability (e.g.,
great seasonal and/or annual variability in recruitment by common
species, recruitment limitation for most species, and a high turnover
rate detected by frequent sampling). Some predictions of the theory of
island biogeography were also met by these fish communities (e.g.,
species richness correlated strongly with patch reef area, volume and
relief). and total fish abundance. Some populations also exhibited a
degree of long-term stability. Species diversity [H'] was similar
among different size reefs.
The experimental fishing on piscivores produced a catch composed
mainly of lizardfish, due largely to immigration following the removal
of other, competitively superior, highly resident piscivores.
Scorpionfish and moray eels were also dominant predators. The expected
decreases in catch-per-unit-effort were not realized, except for a
quantitatively insignificant family (hawkfish). Conversely, the catch
of the highly migratory lizardfish actually increased as fishing
progressed. Changes in the catch composition for other piscivores related mainly to major changes in reef size or to patterns of large,
inter-year recruitment fluctuations. Census data confirmed the major
trends indicted by catch results. Sharks and jacks were attracted to
the experimental reefs by spearfishing; the study was unable to
determine whether their piscivorous effect was different between reef
treatments.
Patch reef fish communities at Midway were relatively resilient to
long-term, intense fishing pressure on piscivores. However, enhanced
survival of a large, annual, summer recruitment pulse of a common
cardinalfish, synchronized with a temporary but significant reduction
of lizardfish (the most prevalent piscivore) by fishing, suggested that
an effect of predation on reef fish populations is experimentally
detectable and considerable. However, temporal and spatial variability
in recruitment, and reef size differences and changes in size were the
primary factors responsible for the observed temporal patterns in fish
abundance. COlnmunity analysis involves numerous confounding effects
and requires the most careful interpretation for valid conclusions.<br>xvi, 321 leaves, bound : ill. ; 29 cm.
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Castro, Kreder Natasja. "In vitro studies on radiation effects and radiosensitization: HDR vs LDR and cytotoxic agents FISHing for, breaking and rejoining radiosensitivity /." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/88010.
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Harding, Craig Thomas. "Tracking African penguins (Spheniscus demersus) outside of the breeding season: Regional effects and fishing pressure during the pre-moult period." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/6565.
Full textAbstract:
African penguins (Spheniscus demersus) have experienced a 60% population decline in the past 30 years due to an eastward shift in the relative abundance of their main food source, anchovy (Engraulis encrasicolus ) and sardine (Sardinops sagax). This shift may be exacerbated by pressure from the small-pelagic fishery targeting these species. A lack of knowledge regarding foraging areas when not breeding has been identified as a deficiency in management planning for African penguins. Satellite transmitters were deployed on 20 adults during the pre-moult foraging period from colonies on the west coast (Dassen Island, n=10) and south coast (Bird Island, Algoa Bay, n=10) of South Africa. Kernel density analyses were produced using nightly locations to create foraging range maps, which were compared to catches made by the small-pelagic fishery during September-December 2012. Birds from the two colonies differed in their foraging strategies. Compared to penguins from Bird Island, those from Dassen Island spent more than six times the number of nights beyond the foraging range used during the breeding season (40 km from their colony). Birds from Dassen Island typically made long, looping trips more than 300 km away from the colony, and travelled further and at higher daily rates to foraging areas than individuals from Bird Island, feeding outside areas where fishing activity was highest. Kernel density analysis showed the foraging range of Dassen Island penguins was between Cape Columbine and the central Agulhas Bank. Individuals from Bird Island continued to central place forage, typically staying within 35 km of the colony. Penguins from Dassen Island that remained on the west coast had to compete with higher levels of fishing pressure than penguins from Bird Island. More than 70% of the fleet-wide, 2012 purse-seine catch occurred within the area where Dassen Island penguins spent 50% of their time. These colony-specific characteristics suggest that management plans for African penguins need to be regionally targeted and incorporate larger foraging ranges during the pre-moult period for birds from western colonies. The larger foraging ranges and effort demonstrated by birds from the west coast suggest that a combination of the low relative fish abundance and higher commercial fishing pressure may force pre-moulting birds to seek food sources farther from the colony, putting them at higher risk of not surviving the annual moult. This project requires more years of data to ensure these foraging patterns are representative, and to more accurately provide management suggestions directed to alleviate stress on African penguins for long-term protection of this endangered seabird.
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Nogueira, Barbara Galindo. "Aplicação do conhecimento de pescadores artesanais para entender a captura incidental de tartarugas marinhas no sul do Brasil." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/142044.
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Dentro do contexto de crise global pesqueira que afeta tanto a pesca industrial quanto a artesanal, este trabalho visa descrever e analisar a pesca artesanal de emalhe no sul do Brasil, além de estudar a interação entre essa pesca artesanal e as tartarugas marinhas. O capítulo 1 consiste na caracterização social, econômica e operacional da pesca artesanal, avaliando o esforço pesqueiro de suas diferentes modalidades. A análise dos dados fornecidos por pescadores revelou a diferenciação na captura e esforço entre dois grupos de embarcações: barcos até 12,5 metros de comprimento total e barcos acima de 12,5 metros. As entrevistas também geraram uma ilustração que demonstra a sobreposição da área de atuação dos pescadores. Neste capítulo são propostas medidas de gestão da pesca artesanal de emalhe que consideram o rendimento dos pescadores e preservam os recursos pesqueiros. No capítulo 2 foram analisados fatores sociais e operacionais da pesca relacionados à captura incidental de tartarugas marinhas. Entrevistas com pescadores (n=92) e desembarques monitorados pelos pescadores (n=320) registrados em locais de pesca dentro e fora de Unidades de Conservação Marinhas no Rio Grande do Sul e Santa Catarina verificaram a influência do manejo espacial sobre as capturas incidentais. Analisou-se também o conhecimento ecológico local (CEL) dos pescadores sobre as tartarugas marinhas. A criação de zonas exclusivas para a pesca artesanal e o aumento de vistorias às redes de pesca são propostas para reduzir as capturas incidentais pela pesca artesanal de emalhe no sul do Brasil, através do envolvimento dos pescadores nas pesquisas e do co-manejo dos recursos pesqueiros.<br>Within the context of global fishing crisis that affects both industrial and artisanal fisheries, this survey aims to describe and analyze the artisanal gillnet fishery in southern Brazil and study the interaction between this fishing and sea turtles. The chapter 1 consists in social, economic and operational characterization of artisanal fisheries, assessing the fishing effort of different kinds of fisheries. The analysis of data provided by fishermen revealed the differentiation in catch and effort between two vessel’s groups: boats up to 12.5 meters long and boats over 12.5 meters. The interviews also show the spatial overlap of areas of operation of fishers. In this chapter we proposed measures for the management of small-scale gillnet fishing that consider the income of fishermen and preserve fish stocks. In chapter 2 we analyzed social and operational fishing factors related to bycatch of sea turtles. Interviews (n=92) and landings (n=320) recorded in fishing grounds inside and outside of Marine Protected Areas in Rio Grande do Sul and Santa Catarina assessed the influence of the spatial management on bycatch. It analyzed also the local ecological knowledge (LEK) of fishers about sea turtles. The creation of exclusive zones for artisanal fishing and to increase inspections of fishing nets are presented to reduce incidental catches by artisanal gillnet fishing in southern Brazil, such as the involvement of fishermen in research and co-management of resources.
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Warlimont, Petra. "Application of the Tracking and Analysis Framework (TAF) to Assess the Effects of Acidic Deposition on Recreational Fishing in Maine Lakes." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/WarlimontP2002.pdf.
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Chi, Danielle K. "The Effects of Salmon Availability, Social Dynamics, and People on Black Bear (Ursus Americanus) Fishing Behavior on an Alaskan Salmon Stream." DigitalCommons@USU, 1999. https://digitalcommons.usu.edu/etd/4242.
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The primary goals of this research were to investigate 3 ecological factors influencing black bear (Ursus americanus) foraging behavior on an Alaskan salmon (Oncorhynchus spp.) stream: fish availability, social dynamics, and human activity. Over 900 observation hours were Jogged at 2 falls from July !-September I 1993-1995; the lower falls were open to public for wildlife viewing, but the upper falls were restricted to research personnel.
In general, black bears responded to differences in fish accessibility on both spatial and temporal scales. All years of the study, 3 indices of bear activity (bear minutes, bear numbers, bout duration) and fish capture rates were significantly higher (all Ps <0 I 0) at the upper falls where fishing opportunities were more abundant. Furthermore, seasonal variation in black bear density was indicative of fluctuations in fish accessibility: bear numbers were highest midseason when fish appeared more abundant, but decreased towards the end of the summer.
Although many bears fished within 3 to 5 m of one another, the majority of intraspecific interactions (65-75%) were benign as opposed to agonistic with a preponderance of "passive deferrals" where bears detoured around rather than confronted conspecifics. Only 5. 7% of all interactions resulted in reversals or circularity, providing some evidence for a linear dominance hierarchy. The most dominant bears fished where salmon were highly accessible for longer periods of time, therefore capturing more fish than subordinates each year. Of interspecific interactions, black bears were more likely to be displaced when encountering brown bears on the same side rather than opposite sides of the creek.
Of 24 recognized bears, 71% were observed from 75-100% of the time at the upper falls; only 8% (2 females) fished solely at the lower falls. Five of 8 bears that fished exclusively at the upper falls (all large males) appeared wary of researchers upon their arrival. Based on quantile regression analyses, we found that visitor numbers acted as a ceiling on fishing duration of black bears at the lower falls in 1994 and 1995. Furthermore, 2 habituated bears seen frequently at the lower falls spent less time in view (maximum values) as visitor group size increased.
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Smedley, Marie A. "Nutritional and environmental effects on triploid Atlantic salmon skeletal deformity, growth and smoltification." Thesis, University of Stirling, 2016. http://hdl.handle.net/1893/23342.
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The Atlantic salmon (Salmo salar) is an iconic species that dominates the global finfish production sector with increasing market demand. The Scottish industry and government alone aspires for expansion of the sector to 210,000 t by 2020 with 154, 000 t produced in 2013. As such, there are pressures to improve sustainable development in particular to minimise the genetic impact of escapees on wild populations and reduce sea lice infection which are required for the granting of “green licenses” in Norway. The use of triploidy has been tested in the 1980’s with little success owing to suboptimal rearing conditions leading to elevated mortalities, poorer growth and a higher prevalence of deformities, in particular of the skeleton. Collectively: recent success of triploid trout farming, expansion to the salmon production sector and potential resulting pressure on wild stocks through escapee increases have reinstated interest to implement artificially induced triploid Atlantic salmon in commercial production. As diploid Atlantic salmon have undertaken extensive domestication to achieve the high quality production and welfare standards observed to date, triploid conspecifics too require husbandry optimisation to realise potential. In particular, industrialisation requires that higher observations of deformities and inconsistent growth trajectories during seawater ongrowing be resolved through optimisation of rearing regimes and subsequent standardization of husbandry protocols. Triploids possess additional genomic material and increased cell size yet reduced frequency that reflects known differences in physiology and supports that, in effect, triploids should be considered as a new species relative to diploid conspecifics. Therefore, this doctoral thesis aimed to study nutrition and temperature effects on triploid Atlantic salmon traits throughout the production cycle from ‘egg to plate’. Nutrition trials aimed to improve growth potential and mitigate skeletal deformities both in freshwater (FW) and saltwater (SW) whilst attempts were made to define a window of smoltification to ensure optimal ongrowing performance. Finally, impacts of embryonic temperature regimes that are known to impact long term performance and deformity development in triploids, were examined in relation to DNA regulation and yolk composition in an attempt to underpin potential mechanisms for the environmental impact of temperature on developmental phenotype. One of the main restrictions to triploid Atlantic salmon implementation is the increased prevalence and severity of skeletal deformities, particularly after the maring phase. The work performed in this thesis first demonstrated that protein and/or phosphorous (P) supplementation throughout SW ongrowing not only reduced the level of severely deformed (≥ 10 deformed vertebrae observable by x-radiography) individuals by 30 % but also sustained 6.8 % faster growth and improved harvest grade compared to triploids fed a standard grower diet (chapter 2). Comparison of x-radiography and severely deformed individuals between harvest and sea transfer highlighted that protein and P supplementation arrested deformity development whereas prevalence increased in triploids fed a standard grower diet. This implied that severe deformities were of FW origin and strongly suggest requirement for improved nutrition in FW to optimise SW performance. Therefore investigation of higher dietary P inclusion in FW was investigated and results showed significantly reduced number of deformed vertebrae and no severely deformed individuals in those fed 19.7 g total P Kg-1 compared with those fed 13.0 & 16.7 g total P Kg-1 (chapter 3). Most deformities were localised in the central (vertebrae 27 – 31) and caudal (vertebrae 52 – 57) regions for all treatments. However, triploids fed lower dietary P displayed a particular increase in prevalence within the tail region (vertebrae 32- 47) which is consistent with SW ongrowing reports and results from chapter 2, further highlighting FW origin of higher vertebral deformities reported in SW ongrowing in triploids. Higher P supplementation in FW also significantly improved growth in triploid parr compared to diploids and lower supplementation. However, this effect did not transpire in later FW smolt stages where weights were significantly higher in triploids fed lower compared to higher P supplementation. Expression of target genes involved in osteogenesis and bone P homeostasis in vertebrates were then analysed and a ploidy effect of osteogenic genes alp, igf1r and opn as well as a dietary effect on P homeostasis gene fgf23 was apparent in the parr stages but not smolt. In addition, stronger ploidy-diet effects were also observed in parr stages for whole body mineral concentrations. Collectively, growth, gene expression and whole body mineral content results indicate these earlier parr life stages may be more sensitive to P supplementation. This pronounced effect may be a consequence of seasonal accelerated growth associated with this period, where higher temperatures were also observed. The potential for shorter P supplementation windows in commercial production was addressed in chapter 4 with hope to cut economic cost to raw mineral inclusion in feed and also mitigate potential anthropogenic eutrophication on the environment that may be induced by P leached through uneaten feed and faeces. Triploids were fed higher dietary P (17.4 g total P Kg-1) until either early (5 g) or later (20 g) parr stages, or smolt (83 g) and monitored for performance throughout freshwater (FW) development. During later parr development (30 g), x-radiography assessment demonstrated that increased dietary P reduced the number of deformities and severely deformed individuals with no indication that feeding P for shorter windows improved skeletal integrity. Hence, P supplementation may be required throughout FW development for optimal skeletal performance. In addition, no differences in deformities were observed between triploid treatments at smolt. An effect of dietary P supplementation on whole body mineral concentration was observed in the early and later parr stages that was not as pronounced as smolt, which is consistent with results in chapter 3. Together, these results indicate that skeletal assessment during early developmental stages may not reflect smolt performance most likely as a consequence of seasonal effects of improved linear growth in the cooler winter temperatures prior to smolt where reversible deformities observed at parr may also be alleviated. In the same study (chapter 4), the inclusion of the probiotic Pediococcus acidilactici (Bactocell™) was also tested as a means to enhance gut assimilation as suggested in previous studies and therefore reduce the levels of P supplementation. Results clearly indicate superior skeletal performance in parr (30 g) as well as significantly less deformed vertebrae and no severely deformed individuals. However, at smolt (~83g), no effects of the dietary probiotic treatment were observed which may also be attributed to seasonal effects. Overall, nutritional research clearly indicate triploids require higher dietary P for optimal growth and skeletal development, which although is not consistent between life stages, is ultimately required throughout FW for optimal skeletal development at smolt. The use of probiotics offer a promising avenue for reduced P requirement in FW feed and further research should verify results and assess long-term performance. Timing of SW transfer according to correct parr-smolt transformation (PST) is essential for survival and growth performance in ongrowing where feeding and growth rate accelerate post-transfer. So far, SW transfer regimes and in particular the smoltification ‘window’ remains loosely defined in triploid Atlantic salmon and it is crucial that this be addressed to ensure optimal ongrowing survival and performance.
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Morrison, Jean. "Bajau gender : a study of the effects of socio-economic change on gender relations in a fishing community of Sabah, East Malaysia." Thesis, University of Hull, 1993. http://hydra.hull.ac.uk/resources/hull:3711.
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Marzuki, Marza Ihsan. "VMS data analyses and modeling for the monitoring and surveillance of Indonesian fisheries." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2017. http://www.theses.fr/2017IMTA0012/document.
Full textAbstract:
Le suivi, le contrôle et la surveillance (MCS) des pêches marines sont des problèmes essentiels pour la gestion durable des ressources halieutiques. Dans cette thèse, nous étudions le suivi spatial des activités des navires de pêche en utilisant les données de trajectoire du système de surveillance des navires (VMS) dans le cadre du projet INDESO (2013-2017). Notre objectif général est de développer une chaîne de traitement des données VMS afin de: i) effectuer un suivi de l'effort de pêche des flottilles de palangriers indonésiens, ii) détecter les activités de pêche illégales et évaluer leur importance. L'approche proposée repose sur des modèles de mélange gaussien (GMM) et les modèles de Markov cachés (HMM), en vue d'identifier les comportements élémentaires des navires de pêche, tels que les voyages, la recherche et les activités de pêche, dans un cadre non supervisé. Nous considérons différentes paramétrisations de ces modèles avec une étude particulière des palangriers indonésiens, pour lesquels nous pouvons bénéficier de données d'observateurs embarqués afin de procéder à une évaluation quantitative des modèles proposés et testés.Nous exploitons ensuite ces modèles statistiques pour deux objectifs différents: a) la discrimination des différents flottilles de pêche à partir des trajectoires des navires de pêche et l'application à la détection et à l'évaluation des activités de pêche illégale, b) l'évaluation d'un effort de pêche spatialisé à partir des données VMS. Nous obtenons de très bons taux de reconnaissance (environ 97%) pour la première tâche et nos expériences soutiennent le potentiel d'une exploration opérationnelle de l'approche proposée. En raison du nombre limité de données d'observateurs embarqués, seules des analyses préliminaires on pu être effectuées pour l'estimation de l'effort de pêche à partir des données VMS. Au-delà des développements méthodologiques potentiels, cette thèse met l'accent sur l'importance de la qualité de données d'observation en mer représentatives pour développer davantage l'exploitation des données VMS tant pour la recherche que pour les questions opérationnelles<br>Monitoring, control and surveillance (MCS) of marine fisheries are critical issues for the sustainable management of marine fisheries. In this thesis we investigate the space-based monitoring of fishing vessel activities using Vessel Monitoring System (VMS) trajectory data in the context of INDESO project (2013-2017). Our general objective is to develop a processing chain of VMS data in order to: i) perform a follow-up of the fishing effort of the Indonesian longline fleets, ii) detect illegal fishing activities and assess their importance. The proposed approach relies on classical latent class models, namely Gaussian Mixture Models (GMM) and Hidden Markov Models (HMM), with a view to identifying elementary fishing vessel behaviors, such as travelling, searching and fishing activities, in a unsupervised framework. Following state-of-the-art approaches, we consider different parameterizations of these models with a specific focus on Indonesian longliners, for which we can benefit from at-sea observers¿ data to proceed to a quantitative evaluation. We then exploit these statistical models for two different objectives: a) the discrimination of different fishing fleets from fishing vessel trajectories and the application to the detection and assessment of illegal fishing activities, b) the assessment of a spatialized fishing effort from VMS data. We report good recognition rate (about 97%) for the former task and our experiments support the potential for an operational exploration of the proposed approach. Due to limited at-sea observers¿ data, only preliminary analyses could be carried out for the proposed VMS-derived fishing effort. Beyond potential methodological developments, this thesis emphasizes the importance of high-quality and representative at-sea observer data for further developing the exploitation of VMS data both for research and operational issues
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Bealey, Roy Steven John. "Short-term changes to the life history of shad, Pomatomus saltatrix (Perciformes: Pomatomidae), in Southern Angola." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1017211.
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A general lack of biological information is hampering the effective management of Angola’s fisheries. While this lack of information is largely a result of the country’s extended civil war that ended in 2002, the subsequent rapid expansion of fisheries is most likely impacting fish abundance and influencing the biology of this regions fishes. Besides the influence of fisheries, the southern Angolan coastal region is considered to be a climate change “hotspot” due to rapidly (>0.8°C/decade) increasing water temperatures. These changes are thought to drive further changes to the biology of fishes. It is therefore critical to provide baseline biological information and to identify the impacts of exploitation and warming on the biology of southern Angolan fishes. Pomatomus saltatrix is a warm-temperate marine fish species that forms an important component of fisheries throughout its broad distribution. P. saltatrix is a migratory predator that displays variable growth and maturity schedules. Typically it is heavily targeted in a range of coastal fisheries of Angola and is therefore an ideal candidate to study the biological impacts of exploitation and climate change. The aim of this study was to provide the first description of P. saltatrix biology in Angola and examine recent changes of the species biological parameters in an attempt to uncouple fishery driven from climate driven changes. Samples of P. saltatrix were collected monthly using standardised biological methods from June 2005 to December 2006 (period 1) and from June 2012 to February 2013 (period 2). The average (508mm – 1st period, 462mm – 2nd period) and maximum (760mm – 1st period, 746mm – 2nd period) size of P. saltatrix was smaller during the second period to suggest selective overharvesting of large individuals by developing fisheries. Angolan P. saltatrix grew very rapidly in their first year and thereafter, relatively slowly when compared to other populations globally. However, fish grew faster (ω = 103 – 1st period, ω = 124 – 2nd period), matured at a larger size (303mm - 1st period, 336mm - 2nd period) and younger age (0.83 years - 1st period, 0.67 years – 2nd period) during the second period. Peaks in reproductive activity remained similar (November) during both periods but a temperature anomaly appears to have influenced spawning during period 2. Sardinella aurita was the dominant prey during both periods but a greater dependence upon mugilids was observed during the second period. Although the changes in life history were not statistically significant, the faster growth observed during period two could be attributed to both increasing temperature and/or exploitation. Fishes generally grow faster, mature smaller and attain a smaller maximum size in warmer temperatures. Fisheries targeting small and large specimens of a species (as observed in this study) largely have the same impacts as ocean warming. With rapidly increasing water temperatures and exploitation rates, faster growth and earlier maturation of P. saltatrix populations will mitigate the impacts of exploitation in the short-term. However, the sustainability of Angola’s P. saltatrix stock is questionable as phenotypic adaptation will have a limited thermal scope and overexploitation will, like in all fisheries, negatively influence recruitment. Ultimately, strict monitoring, regulation and control will be necessary to ensure the sustainability of the P. saltatrix resource in Angola as it continues to face increasing anthropogenic and environmental pressures. Management guidelines and future research suggestions are therefore outlined with reference to the results of analyses conducted during this study.
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Stäbler, Moritz [Verfasser], and Axel [Akademischer Betreuer] Temming. "Effects of and on the food-web when fishing for maximum sustainable yields in the southern North Sea / Moritz Stäbler ; Betreuer: Axel Temming." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2017. http://d-nb.info/114386865X/34.
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Santos, Paulo Roberto Santos dos. "A pesca artesanal da Miragaia (Pogonias cromis, Scieanidae) e consequências da sobreexplotação, no estuário da Lagoa dos Patos." reponame:Repositório Institucional da FURG, 2015. http://repositorio.furg.br/handle/1/6060.
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Previous issue date: 2015<br>O aumento na abundância de peixes não residentes da zona estuarina, atraem o interesse da frota
pesqueira, que atua sobre os estoques de forma intensa, muitas vezes levando a sobreexplotação.
No estuário da Lagoa dos Patos, a Miragaia (Pogonias cromis), é um peixe estuarino dependente
que por muitos anos foi um importante recurso pesqueiro, e hoje encontra-se sobreexplotado e
ameaçado de extinção. As capturas que atingiram 1400 t em 1976, decaíram posteriormente e
foram inexistentes nos anos de 2004, 2005, 2008, 2009 e 2010. Mas recentemente, se observa o
aumento dos desembarques na região. A partir disso, a presente dissertação tem por objetivo
descrever a pesca artesanal da Miragaia no estuário da Lagoa dos Patos e analisar o efeito da
sobreexplotação no ciclo reprodutivo da população remanescente na região. No primeiro capítulo
intitulado "A pesca artesanal da Miragaia (Pogonias cromis, Scieanidae) no estuário da Lagoa dos
Patos", é discutida a hipótese de que os maiores valores de esforço e CPUE são encontrados no
mesmo período de maior abundância da espécie no estuário, e verifica-se a influência do esforço
de pesca nas variações da CPUE. De forma complementar, se confirma a distinta composição dos
desembarques entre o período de desova e o resto do ano, a predominância de adultos no período
de desova evidencia o aumento da abundância. No segundo capítulo intitulado "O efeito da
sobreexplotação no ciclo reprodutivo da Miragaia (Pogonias cromis, Scieanidae)" é discutido a
redução da idade e tamanho de primeira maturação sexual e consequentemente fecundidade dos
exemplares, como consequência da sobrepesca sofrida pela espécie em anos anteriores. Os
resultados encontrados mostram a situação preocupante da população de Miragaias no estuário da
Lagoa dos Patos, onde a manutenção da intensidade pesqueira pode levar ao colapso da atividade
e posterior extinção local da espécie.<br>The increase in the abundance of non-resident fish estuarine zone attract the interest of the fishing
fleet, which operates on the intensely stocks, often leading to overexploitation. In the estuary of
Patos Lagoon, the Black drum (Pogonias cromis) is an estuarine-dependent fish who for many years
was an important fishing resource, and today is overexploited and threatened with extinction.
Catches reached 1400 t in 1976, declined later and were negligible in the years 2004, 2005, 2008,
2009 and 2010. But recently observed increased landings in the region. Thus, this thesis aims to
describe artisanal fishing of Black drum in the estuary of Patos Lagoon and analyze the effect of
v
overexploitation in the reproductive cycle of the remaining population in the region. In the first
chapter entitled "The artisanal fishery Black drum (Pogonias cromis, Scieanidae) in the estuary of
Patos Lagoon," discusses the hypothesis that higher values of effort and CPUE are found in the same
period of greatest abundance of the species in the estuary, and there is the influence of fishing effort
in changes in CPUE in a complementary way confirms the different composition of landings
spawning periods for the rest of the year, the prevalence of adults in spawning highlights the
increasing abundance. In the second chapter entitled "The effect of overexploitation in the
reproductive cycle of Black drum (Pogonias cromis, Scieanidae)" is discussed reducing the age and
size at first sexual maturity and consequently fertility of copies as a result of overfishing suffered by
the species in previous years. The results show the worrying situation of the population of Black
drum in the estuary of Patos Lagoon, where the maintenance of fishing intensity can lead to the
collapse of activity and subsequent local extinction of the species.
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Winn, Jeremy Paul. "Modeling Large Whale Entanglement Injuries: An Experimental Analysis of the Influence of Tissue Compliance, Line Tension, and Draw-Length on Epidermal Abrasion Resistance." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/WinnJP2006.pdf.
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Torres, Edgar. "Effects of the fishing strategies developed by purse seine fleets on tropical tunas and on associated fauna in the eastern Atlantic and eastern Pacific oceans." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20029/document.
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Les pêcheries de thonidés représentent 7.9% de la production mondiale de produits de la mer. La plupart des stocks de thons sont pleinement exploités, et certains surexploités, et tous font face à une pression de pêche croissante. En raison de l'extension des zones de pêche, les évaluations des stocks dépendent en grande partie des captures commerciales. Toutefois, les données commerciales peuvent varier au cours du temps étant donné que les pêcheurs peuvent investir dans des engins de pêche et de l'équipement, s'établir au large des côtes, ou commencer à pêcher dans de nouvelles zones. Peu d'attention a été portée à la réponse des pêcheurs aux mesures de gestion ou aux conséquences de l'investissement technologique. L'objectif de la présente thèse est d'étudier les effets de stratégies de pêche et les réponses adaptatives des flottes de senneurs sur les thons tropicaux et la faune associée dans l'Océan Atlantic Est et dans l'Océan Pacifique Est. Dans un premier temps, nous montrons comment l'introduction de nouvelles technologies a eu un effet direct en augmentant la puissance de pêche, et un effet indirect en entraînant une modification des zones pêche. Nous étudions les effets de deux fermetures spatio-temporelles sur la dynamique de la flotte de senneurs européens. La première mesure de gestion a diminué les jours où des captures sont réalisées, les carrés avec capture à l'intérieur de la zone partiellement fermée, tandis que la pêche sur DCP a été redistribuée à l'extérieur de la zone et aucun changement n'a pas été enregistré pour la pêche sur banc libre. La seconde fermeture de pêche a entraîné une augmentation de toutes les activités de pêche en dehors de la zone. Dans l'Océan Pacifique Est, la flotte de senneurs mexicains a réagit à la fermeture d'une saison de pêche en diminuant le nombre de jours passés à quai. Par conséquent, le nombre de calées sur bancs associés aux dauphins a augmenté, et les niveaux de capture observés avant la mesure de gestion ont été maintenues. Nous analysons les effets des stratégies de senneurs de l'Union Européenne sur les prises accessoires. Nous mettons en évidence que la composition des espèces de requins capturés sous DCP et les raies capturées sur bancs libres ont changé au cours du temps. Nous estimons également que plusieurs types d'espèces peuvent être capturés par mode de pêche<br>Tuna and tuna-like fisheries represent 7.9% of the global production of marine capture fisheries. Most tuna stocks are fully exploited and some overexploited, facing growing fishing pressures. Due to the extent of fishing grounds, stock assessments depend largely in commercial data, which vary over time because fishermen may invest in fishing technology, expand offshore, or start fishing in different areas. However, little attention has received the responses of fishermen facing management regulations or the effects resulting from technological investment. For these reasons the aim of this study was to investigate the effects of fishing strategies developed by purse seine fleets on tropical tunas and on associated fauna in the eastern Atlantic and eastern Pacific oceans. The continuous introduction of new fishing technology in the French fleet in the 1980s and the 1990s evidenced a direct increase in fishing power when large yellowfin in free-swimming school is targeted and likely an indirect effect by modifying the fishing grounds characterizing FAD-fishing on small size categories. The consequences of the two time-area closures on the spatio-temporal dynamics of the European Union fleet were investigated. The regulation on FADs resulted in a decrease in the days with catch and successful squares inside the restricted area, reallocating FAD-fishing outside the area while no change in free-swimming school fishing was observed. The no-take time-area increased all fishing activities outside the restricted area with apparently no gain in terms of protection of juveniles. In the eastern Pacific as a response to a closed season the Mexican fleet reduced days in port and consequently the number of sets on dolphin-associated schools increased, maintaining the catch levels observed before the regulation. The study of the effects of the EU fleet fishing strategies on bycatch over two time periods showed that the species composition of sharks caught on FADs and may be for rays caught on free-swimming schools changed over time. We also estimated the total number of species that can be potentially be caught by fishing mode
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Simpson, Anne W. "An Investigation of the Cumulative Impacts of Shrimp Trawling on Mud Bottom Fishing Grounds in the Gulf of Maine: Effects on Habitat and Macrofaunal Community Structure." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/SimpsonAW2003.pdf.
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Alarcón, Sergio Eduardo Neira. "Assessing the effects of internal (trophic structure) and external (fishing and environment) forcing factors on fisheries off central Chile : basis for an ecosystem approach to management." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/6217.
Full textAbstract:
Includes abstract.<br>Includes bibliographical references (p. 227-253).<br>Human perception of sea fisheries has evolved from an inexhaustible resource paradigm towards a generalized concern on the degraded state of fish stocks and ecosystems. Accordingly, fisheries science and management are expanding from the traditional single-species approach towards an ecosystem approach to fisheries. Marine communities are organized as webs of interactions that are affected by external natural (climate) and anthropogenic (fishing) forcing, with their relative effects poorly known, but hypothesised to strongly depend on internal food web structure (i.e., who eats and controls whom). This thesis approaches relevant ecological considerations for an ecosystem approach to fisheries in the upwelling ecosystem off central Chile (33ºS-39ºS). The main objective is to assess the effects of internal (trophic structure) and external (fishing and environment) forcing factors at the fish stock and food web level in the study area. The methodology includes i) the construction of snapshot and dynamic food web models to test hypothesis of changes in the food web in the last century, and the relative contribution of fishing, trophic controls and bottom-up environmental variability to those changes, ii) the computation and analysis of a set of ecosystem indicators to test hypotheses of changes in different aspects of the exploited community (mean trophic level, age and length at maturity, network properties and system variability), iii) the analyses of the relationships between time series of abundance of species with known trophic interactions (Chilean hake-red squat lobster and Chilean hake-small pelagic fish) to test hypothesis of top-down and bottom-up control versus alternative hypotheses of fishing and/or environmental control in the same populations, and iv) simulation experiments to test hypotheses of ecosystem change and recovery under fishing and environmental forcing. Models and indicators are constructed using data series of abundance, catches, production, consumption and diets of the main functional groups in the study area. Snapshot and dynamic food web models are constructed and analyzed using the Ecopath with Ecosim software version 5.1 and routines therein. The observed trends in indicators and model results are in accordance with what is theoretically expected in stressed ecosystems (shift towards a food web dominated by short-lived, low trophic level and high turnover rate species), and suggest that the food web could be in a state that is more susceptible to external forcing. Fishing and the environment (bottom-up anomaly in PP) may have affected the upwelling ecosystem off central Chile both at the stock and at the food web level between 1970 and 2004. The effects of these forcing factors may have been mediated by trophic controls operating in the food web. There is also evidence to support the hypothesis that trophic controls beyond fishing, e.g., trophic (internal) and environment (external) may operate in the analysed populations and this information should be considered in their assessment and management. While target objectives are set and agreed, it is proposed that the main objective for the ecosystem approach to fisheries should be to avoid fishing-induced regime shifts, since results from simulation experiments suggest that fishing can induce ecosystem changes of lower recovery than bottom-up forcing.
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Andrade, Joana Isabel da Silva. "Effects of cyanide exposure on marine fish with emphasis to Amphiprion spp." Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14774.
Full textAbstract:
Mestrado em Biologia Marinha<br>Tropical coral reefs have a high importance on marine ecosystems due to their
high productivity and biodiversity. However, these ecosystems are facing a
growing number of both natural and anthropogenic threats. Cyanide fishing is
a destructive technique to capture live reef fish, both for human consumption
and to supply the marine aquarium industry. Clownfish and damsels (
Family Pomacentridae) are the most heavily traded group of marine aquarium
fish and consequently also some of the most commonly targeted fishes by this
illegal fishery. Cyanide (CN-) is considered to be a potent inhibitor of enzymatic
pathways involved in respiration and other physiological functions in fish and
when used in acute doses can accumulate in body tissues and fluids,
negatively affecting several enzymes. In the present study, we analyzed the
effects of different concentrations of CN- pulse exposures (mimicking cyanide
fishing) in survival and biomarker activity in two different sizes of Amphiprion
ocellaris and calculated their respective LC50. Subsequently, the same species
was exposed to a sublethal concentration of CN- (25 mg L-1) under global
warming scenarios predicted for 2100 (29 °C and 32 °C). Eight different species
of pomacentrids were also pulse exposed to a concentration of 50 mg L-1 of
CN- to investigate interspecific variability in their tolerance to CN- poisoning.
Our data revealed that LC50 of small fish is nearly half of that estimated for
medium sized fish (28.45 mg L-1 and 50 mg L-1 of CN-, respectively). It was also
possible to demonstrate that the increase of seawater temperature, by itself,
can cause mortality in clownfish, and that mortality promoted by CN- fishing
will be magnified at higher temperatures. Finally, it is confirmed that
vulnerability to CN- poisoning may vary interspecifically, even in species which
are closely related phylogenetically. The clownfish A. ocellaris displayed the
highest tolerance to CN- poisoning among all tested pomacentrids. Overall, it
is mandatory to effectively ban CN- fishing from tropical coral reefs, as the
damage this practice already causes in the oceans of today will be largely
magnified in the oceans of tomorrow.<br>Os recifes de coral tropicais têm uma grande importância nos ecossistemas
marinhos, devido à sua produtividade e biodiversidade. No entanto, estes
ecossistemas estão a enfrentar um crescente número de ameaças naturais e
antropogénicas. A pesca com cianeto é uma técnica destrutiva para capturar
peixes vivos de recife, tanto para o consumo humano como para abastecer a
indústria de aquários marinhos. O peixe-palhaço e as donzelas (Família
Pomacentridae) são o grupo de peixes mais comercializados em aquariofilia e,
consequentemente, são dos peixes mais capturados com esta pesca ilegal. O
cianeto (CN-) é considerado um potente inibidor das vias enzimáticas
envolvidas na respiração e outras funções fisiológicas no peixe, que quando
utilizado em doses agudas pode acumular-se em tecidos e fluidos corporais,
afetando negativamente várias enzimas. No presente estudo, foram
analisados os efeitos das diferentes concentrações de CN- (imitando a pesca
com cianeto) na sobrevivência e atividade dos biomarcadores em dois
tamanhos diferentes de Amphiprion ocellaris e calculado o respetivo LC50.
Posteriormente, a mesma espécie foi exposta a uma concentração sub-letal de
CN- (25 mg L-1) sob o cenário de aquecimento global previsto para 2100 (29 °C
e 32 °C). Oito espécies diferentes de pomacentrídeos foram expostos a uma
concentração de 50 mg L-1 de CN- para investigar a variabilidade
interespecífica na sua tolerância ao envenenamento por cianeto. Os nossos
dados revelaram que o LC50 de peixes pequenos é quase a metade do que o
estimado para os peixes de tamanho médio (28,45 mg L-1 e 50 mg L-1 de CN-,
respetivamente). Também foi possível demonstrar que o aumento da
temperatura da água do mar, por si só, pode causar mortalidade no peixepalhaço,
e que a mortalidade promovida pela pesca com cianeto será
aumentada a temperaturas mais elevadas. Finalmente, confirma-se que a
vulnerabilidade ao envenenamento por cianeto pode variar
interespecificamente, mesmo em espécies que estão estreitamente
relacionadas filogeneticamente. O peixe-palhaço A. ocellaris apresentou a
maior tolerância ao envenenamento por cianeto relativamente a todos os
pomacentrídeos testados. Por isso, é obrigatório proibir eficazmente a pesca
com cianeto nos recifes de coral tropicais, pois o dano que esta prática faz nos
oceanos de hoje será largamente ampliado nos oceanos de amanhã.