To see the other types of publications on this topic, follow the link: Sea Fish.
Dissertations / Theses on the topic 'Sea Fish'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Sea Fish.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Abuzinadah, Osama A. H. "Studies on Red Sea fish." Thesis, Swansea University, 1990. https://cronfa.swan.ac.uk/Record/cronfa43156.
Full text
2
Baudron, Alan Ronan. "Length-based modelling of North Sea fish growth." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=192287.
Full textAbstract:
This thesis focuses on the temporal variations in growth affecting commercial species of fish in the North Sea. The aims were firstly to review the modelling tools available to study fish growth in the North Sea, and secondly to investigate the implications of the observed increase in North Sea temperature on the growth of commercial fish species. The von Bertalanffy growth function (VBGF) is a reliable and flexible model to study fish growth and was employed throughout this thesis. The age-length keys (ALKs) used to model fish growth were length-stratified samples and were showed to result in biased VBGF parameter estimates. Thus, ALKs should be corrected by the length frequency observed in the population when possible. A warming trend has been observed in the North Sea over the last decades, with an overall increase of 1 °C in the northern North Sea. These warming temperatures were significantly linked with a decrease in asymptotic length (L∞) and an increase in the rate at which L∞ is reached (K) observed for North Sea haddock (Melanogrammus aeglefinus). Incorporating the temperature covariate into an extended VBGF to model haddock growth allowed quantifying a decrease in weight-at-age up to 40% at age 10 occurring at warmer temperatures, resulting in a 20% loss of individual yield. A meta-analysis was then conducted across North Sea commercial species and confirmed that most species experienced a synchronous decline in L∞, with the exception of cod (Gadus morhua) and sprat (Sprattus sprattus). This strongly suggests that the increase in temperature is the cause of the changes observed in VBGF parameters. Overall, the findings suggest that, in many commercial fish species of the North Sea, the increase in temperature induced a faster growth towards a smaller asymptotic length. This is likely to jeopardize fisheries yields and thus to affect the economic efficiency of North Sea fisheries. The results of this thesis advocate that the effect of temperature on growth is large enough to be incorporated into North Sea fish stock assessment models.
3
Milligan, Rosanna J. "Natural and anthropogenic drivers of deep-sea fish populations." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/5981/.
Full textAbstract:
Deep-sea demersal fish are likely to be highly important in structuring deep-sea ecosystems, but a paucity of data means that relatively little is known about the spatial and temporal processes that influence their distributions or how these may change at different scales of observation. As human activities continue to expand into deeper waters, the importance of understanding these processes is becoming increasingly urgent. The oil and gas industry are expanding into deeper waters as coastal oil reserves diminish, but potential long-term effects on the benthos are unknown. Time-lapse photographic data collected from within an active oil field on the Angolan continental slope (tropical eastern Atlantic) detected no significant differences in the community composition of fish compared to a reference site. Significant seasonal changes in the total abundance of demersal fish were detected however, with >20-fold increases in abundance recorded from the oil-field observatory. These results suggest that the deep-sea environment in this region is likely to be highly dynamic over seasonal and decadal timescales, and some possible drivers are discussed. Understanding the spatial distributions of fish is important in understanding their potential ecological roles within an ecosystem and how they may benefit from spatially-explicit management measures. In the bathyal NE Atlantic, the demersal fish communities associated with cold-water corals (CWC) appeared to be influenced by processes operating at multiple spatial scales. At the broadest scales (100s km), depth was a significant predictor of community composition, while habitat type was significant at the finest scales (m). These results highlight the need to account for the effects of scale in observational research and may explain why no consensus has thus far been reached regarding the role of CWC habitats for deep-water fish in the NE Atlantic and provide a possible framework for approaching future deep-water community studies. In abyssal depths, the importance of habitat heterogeneity in structuring fish communities has never been previously studied. Investigations of the spatial distributions of demersal abyssal fish around a small (c. 250 m high) abyssal hill showed that the distribution pattern of the total fish fauna and the two dominant taxa were not significantly different from random. Random distributions are unusual in nature and these results suggest that the environment may be essentially homogeneous to abyssal fish at spatial scales between 100 m – 10 km and suggests no influence of the abyssal hill on the fish fauna. The results highlight the great potential value of autonomous vehicles in extending abyssal research over broader spatial scales. Experimental studies investigating the effects of large-scale ecological processes on deep-water ecosystems are often unfeasible. Mathematical models can provide an alternative methodology, but have not been widely applied to the deep sea. In Chapter 5, a simple mathematical model was developed to explore the effects of large, transient resource pulses on the population dynamics of the abyssal holothurian Amperima rosea. Large, apparently transient increases in the biomass of this species have been observed at the Porcupine Abyssal Plain during two “Amperima events”, but the mechanisms leading to the increases remain unclear. The simulations showed that Amperima biomasses within the observed range of the smaller “Amperima event” could be simulated in some circumstances following the addition of a single, large resource pulse (10000 – 20000 g POC ha-1) to the model, which led to a short-term, transient increase in Amperima biomass before a return to previous levels. None of the simulations produced unstable population dynamics. While the scarcity of empirical data from the PAP means that these results must be treated cautiously, they highlight the potential for temporal changes in food supply to rapidly alter the dynamics of abyssal populations.
4
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.
Full text
5
Sullivan, Katherine B. "Replacement of fish meal by alternative protein sources in diets for juvenile black sea bass." View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-3/sullivank/katherinesullivan.pdf.
Full text
6
Newton, Paul William. "The trophic ecology of offshore demersal teleosts in the North Irish Sea." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250301.
Full text
7
O'Sullivan, Martha. "Population structure of demersal fish species in the north eastern Atlantic." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources. Restricted: no access until Dec. 31, 2010. Online version available for University members only until June 2, 2011, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=26063.
Full text
8
Ok, Meltem. "Evaluation Of The Demersal Fish Assemblages Of The Northeastern Levant Sea." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615068/index.pdf.
Full textAbstract:
Ecosystem-level changes have taken place in the Mediterranean Sea over the last decades due to both anthropogenic interferences and natural perturbations. Compared to the western Mediterranean Sea, influences of these factors especially on flora and fauna characteristics are much more dramatic and intense in the eastern part, particularly in the northeastern Levant Sea where the study area is located. In this study, life history traits of some core species (both native and immigrant) occupying the continental shelf of the northeastern Levant Sea were studied in this changing ecosystem to improve limited ecological understanding of the demersal fish assemblages of the northeastern Levant Sea. For this purpose, the annual patterns in allocation and utilization of energy in demersal fish species, temporal and bathymetrical trends in fish distribution with respect to biological requirements of the species and strategies adapted by the species in growth, reproduction and energy storage were investigated by examining growth parameters, biological indices and abundance and biomass variations. Influences of environmental variables on spatiotemporal distribution and biological characteristic of Mullus barbatus were also explored by generalized additive models. Biological data were collected at monthly intervals between May 2007 and May 2010 by trawl sampling while sample collection of environmental variables (temperature and salinity) was performed from December 2008 to May 2010. Results of this study reveal that the components of the demersal fish assemblage in the region fulfill their biological activities within a short period of time when the highest productivity is reached in the area. Moreover, results indicate that within this short period of time, some native components of the demersal fish assemblages studied (Mullus barbatus and Pagellus erythrinus) exhibit strategies such as fast growth, early maturation, short reproduction season, secondary spawners to cope with the environmental peculiarities. On the other hand, the successful exotic colonizers develop strategies as well but these successful immigrants also use time (Lagocephalus suezensis) and space (depth) (Upeneus pori) slot that the native species avoid. In some of the species examined (Mullus barbatus and Lagocephalus suezensis), growth is fast, sexual maturity is early, reproduction period is short, and reproduction potential is high. With the peculiar environmental condition, these life history traits are attributed to the &ldquor-strategy&rdquo
of the species. In this study, generalized additive models of Mullus barbatus explain 81.5 % variations in Gonadosomatic Index (GSI), 55.2 % in Hepatosomatic Index (HSI) and 43.9 % in Condition Factor (K). The time component in the GAM model captures the same cyclic pattern observed in GSI of Mullus barbatus. Besides, The GAM results suggest that the highest GSI values associated with the bottom water temperature are between 18 &ndash
19 °
C while the partial effect of bottom salinity is at 38.7 psu. A positive effect of depth on GSI of the species starts after 60 meters depth and increasing trend continues until 125 meters depth and then decreases. The HSI results are almost identical to GSI outputs indicating that the effects of the parameters concerned act in a similar manner. The results of the GAM models failed to explain influence of environmental parameters on vertical and seasonal distribution of adult Mullus barbatus. However 83.5 % variances were explained in distribution of juveniles. The salinity and temperature have the highest impact on the distribution of juveniles among the parameters evaluated. The results indicate that the occurrence of Atlantic Water in the area has a positive influence on M. barbatus, particularly on the recruits through either by its low salinity or by another factor associated with this water mass. The vertical distribution range are set by the high temperatures (>
27 °
C) at the shallow depths during summer and the low temperatures on the shelf break zone (<
16 °
C). A comparison of vertical abundance distribution of Mullus barbatus and the vertical temperature variations indicate that the species may tolerate up to 27 °
C and then individuals move to the deeper depths so that to the cooler waters when the temperature exceeds their tolerance limit. As well as the life history traits adopted by the species, there are some other factors providing advantages to the species. The fisheries regulations, particularly the time limits applied in the area are in favor of the species especially of pre-recruits. In the study area the pre-recruitment phase and summer YOY aggregations in shallow waters of most species studied in this thesis take place during a time when the fishing season is closed.
9
Wilson, Randall. "Blue fish in a dark sea : police intelligence in a counterinsurgency." Thesis, University of Buckingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.574491.
Full textAbstract:
This work is the result not only of research conducted in fulfillment of degree requirements of the University of Buckingham/BUCSIS but also of my experiences in the field of law enforcement, police intelligence and counterinsurgency over the past twenty three years. It has been my privilege to serve with and advise the police forces of a number of nations beset by insurgencies. These include the highly visible conflicts in Iraq and Afghanistan as well as in other unhappy locations where the stakes were equally high but the coverage considerably less. The opportunity to observe, practice and learn in such environments has done much to inform my thinking and writing about police intelligence in a counterinsurgency. This effort is not meant to be an exhaustive treatment of all -aspects of the subject. Instead, my aim has been to inform both the policy expert and the academic of the existence and potential uses of police intelligence in counterinsurgency. Given that my target audience is largely non-specialists I have opted to present my thoughts and research in a more general, strategic level format and have delved into the specifics of methodology only where such information appeared to me to be a prerequisite for comprehension of the application. The method I have selected to articulate my thoughts has been to present first an overview of what I believe are the salient points regarding the most efficacious uses of police intelligence in a counterinsurgency. Following this I have elected to present separate sections, each dealing with an overview and application of that area of police intelligence. These areas were selected as being ubiquitous in the field. Other quite interesting efforts such as pseudo- operations were not examined due their inclusion in a given counterinsurgency being driven more by tactical opportunity than universal strategic applicability. I have also included a short examination of a current counterterrorism effort which I feel illustrates some important aspects of our topic. The final section is a presentation of the most salient points of the previous sections as well as a summary of the applicability of police intelligence to counterinsurgency. The existence of police intelligence and its unique but all too often marginalized capacity for uncovering and destroying the prime movers of an insurgency is, in my opinion, something which must be re-examined and enabled in all counterinsurgencies. It is by no means a panacea for civil strife but as an integral component of a combined counterinsurgency strategy, it provides a weapon which is more feared by insurgents than any number of missiles, armored vehicles or boots on the ground. Knowing who they are and where they may be found renders the insurgent visible and touchable. This is the natural role of police intelligence as this work is intended to demonstrate. It is my hope that this work will lead to additional discussion and thought on the integration and application of police intelligence to counterinsurgency. Randy Wilson Kabul, Afghanistan 2011 2.
10
Olson, Carina. "Neolithic Fisheries : Osteoarchaeology of Fish Remains in the Baltic Sea Region." Doctoral thesis, Stockholm : Department of Archaeology and Classical Studies, Stockholm University, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8215.
Full text
11
Martínez, Iñigo. "Demersal fish assemblages around sea bed features : Buzzard oil & gas field platform in the North Sea and Jones Bank, Celtic Sea." Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=183828.
Full textAbstract:
The maximum number (Nmax) of fish was recorded using baited underwater camera (BUC) techniques to study spatio-temporal changes of the fish community in localize areas. In the central North Sea (~100m depth) abundance models revealed that for both, whiting and flatfish, the Nmax was influenced by light level at the time of deployment. Nmax of hagfish was strongly related to current speed in a non-linear way with a predicted upper threshold (~11 cm.s-1) above which Nmax declined. Current speed and inter-annual variation had an important effect on haddock Nmax. Large predators that prompt avoidance mechanisms (e.g. large conger eel, marine mammals and fishing vessels) and bottom current speed >25 cm.s-1 can modify demersal fish behaviour depending on size and species and therefore have important effects on BUC-derived data. The BUC was applied for the first time to the monitoring of the Buzzard platform, a new oil and gas development in the central North Sea that host 12 demersal and benthic fish species. The benthic taxa, flatfish and hagfish, showed higher numbers closer to the platform whilst the most mobile species showed constant numbers (haddock) or highest numbers outside of the 500m of Exclusion Area (whiting). No significant changes in fish diversity were found between the areas surveyed before the platform construction. After the construction, the species richness and diversity were higher outside the 500m Exclusion Area surrounding the platform. Offshore sand banks, like oil platforms, can modify the composition of the local fish abundance. BUC and commercial trawl observations on the Jones Bank (75-150m depth, Celtic Sea) recorded 23 species, the highest richness, on top of the bank and 18 species on the slope and off-bank areas. Conger eel and Nephrops were both absent from the top of the bank site whereas haddock was only observed in the bank area.
12
Fielding, Nicola Jane. "Fish and benthos communities in regenerated dock systems on Merseyside." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.482788.
Full textAbstract:
Restored docks have high amenity, tourism and recreational value. Polluted and unaestheticw ater is a major factor potentially inhibiting redevelopmento f docklands, particularly if the source of water suffers from severe pollution problems. The aims were to examine spatial and temporal patterns of hydrography and ecology of Merseyside Docks. Strategies to develop benthic filter-feeders on both the walls and in the sediments were considered important in maintaining good water quality. In the South Docks, algal blooms were mainly small and short-lived and anoxia was infrequent. In Princes Dock (Central chain) water quality was very good. Morpeth Dock (Wirral chain) suffered from poor water quality. Anoxia resulted in high mortalities of dock fauna and fish and the release of hydrogen sulphide gas. Algal blooms were very large and were maintained over long periods. The dinoflagellate, Prorocentrum minimum, was particularly prevalent. Zooplankton have remained at relatively low densities in the South Docks, particularly in Albert Dock (South chain), probably because of strong competition for food with benthic filter-feeders. In contrast, Morpeth Dock has maintained much higher numbers, probably because of the plentiful food supply and absence of benthos. The benthos of the walls was surveyed. Mytilus edulis is most prominent in Albert and Queens Docks; Ciona intestinalis and Ascidiella aspera are most abundant in Albert and Princes Docks; and, Molgula manhattensis dominant in Brunswick and QueensD ocks. Tiles have been used to follow the pattern of annual successiona nd the effect of timing of available space on this pattern of succession. In contrast to previous years when there had been very little recruitment of Mytilus to the South Docks, Mytilus settlement occurred in Queens Dock during autumn 1995. Experiments aimed at increasing the filter-feeding capacity by introducing Cerastodermae dule (common cockle) and manipulating particle size of the sediment concluded that cockles do not survive in the dock, probably due to occasional low oxygenc on centrations in the hypolimnion, and modification of sediment has very little effect on natural colonization. Experiments examined the impact of filter-feeders on phytoplankton numbers and regeneration of nutrients. Mytilus was shown to have higher clearancer ates( cell mV h' int) than its major competitors( Ciona intestinalis, Styela plicata) on the dock wall. The experiment investigating nutrient release by Mytilus indicates release of phosphate. Fish communities in the South Docks were relatively diverse, with a total of fifteen species of fish being caught. The size/frequency analyses suggest that the majority of fish were juveniles. The occurrence of two sea trout (Salmo trutta) indicates a return of salmonids to the estuary. The use of a capacity model as a management tool is proposed; this has been fitted to the South Docks system with some success.
13
Burpee, Jessica L. "Scaling of mitochondrial respiration in white muscle from an active (Pomatomus saltatrix) and inactive (Centropristis striata ) fish." View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-1/burpeej/jessicaburpee.pdf.
Full text
14
Buch, Tanja B. "Spatial structure of North Sea fishes : theory and application to abundance estimation." Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=237000.
Full text
15
Didrikas, Tomas. "Distribution and activity of pelagic fish - acoustic studies in the Baltic Sea." Doctoral thesis, Stockholm : Dept. of systems ecology, Stockholm university, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-738.
Full text
16
Syahailatua, Augy BEES UNSW. "Biological oceanography of larval fish diversity and growth off eastern Australia." Awarded by:University of New South Wales. BEES, 2005. http://handle.unsw.edu.au/1959.4/22791.
Full textAbstract:
Fish larvae in Australian waters have been studied progressively in the last 2-3 decades including the distribution and abundance of taxa, growth and age, their prey and predators. However, the effect of nutrient limitation on ichthyoplankton is unstudied, particularly in the oligotrophic Australian waters. My study was aimed to examine the effect of natural or anthropogenic nutrients on the abundance, distribution, growth and condition of fish larvae along-shore of the NSW coast (latitude 30-34S), where the East Australian Current departs the NSW coast and generates local upwelling of cool nutrient-rich water. This study shows no significant difference in the total abundance or diversity of either larval fishes amongst the 112 taxa (111 families and 1 order), among regions within or upstream of the upwelling. However in both months, there were distinctive ichthyoplankton assemblages at the family level. The Carangidae, Labridae, Lutjanidae, Microcanthidae, Myctophidae and Scombridae were more abundant in the EAC or oceanic water masses, while the Callionymidae, Clupeidae, Platycephalidae, Sillaginidae and Terapontidae were mostly found in the surface or deep upwelled/uplifted water masses. This pattern is observed in other ichthyoplankton studies and may be a general and useful method to determine mixing of water masses. Larvae of silver trevally (Pseudocaranx dentex) and yellowtail scad (Trachurus novaezelandiae) were generally larger and less abundant in the topographically induced upwelling region, than north of the region in pre-upwelled conditions of the East Australian Current. Both species were mostly at the preflexion stage (less than 4.3 mm in body length and less than 10 days old) in the pre-upwelled conditions, particularly during November, and proportionally more larger and older larvae in the upwelled waters (mostly post-flexion, greater than 4.3 mm in body length and greater than 10 days old). Ages from sagittal otoliths ranged from 2-25 increments (~days) and exhibited linear growth for both species and months over the size range (3-15 mm standard length). The otolith radius-length relationship and the growth rates were similar between species and months, despite the 3-4C difference between months. Overall growth rates of the younger larvae were uniform throughout the entire sampling area (0.5-0.6 mm.d-1), while older larvae grew significantly faster in the upwelled water (0.41 mm.d-1) compared to the non-upwelled conditions (0.34 mm.d-1). Both species tended to be depleted in 13C in the upwelling region (from ???18.5 to ???19.0), consistent with expected ratios from deeper water, whereas the 15N composition tended to increase in Pseudocaranx, but decrease in Trachurus indicating different diets and possibly trophic level. The early life history of both species indicates spawning in pre-upwelled waters, but larval transport into upwelled waters is necessary for faster growth in the post-flexion stage. The assemblage of larval fishes did differ between the upwelled region and a region south of Sydney???s deepwater outfalls, but the difference was ascribed to a latitudinal effect and the EAC. Both larval carangids were enriched in 15N, possibly due to the enriched dissolved organic matter of primary treated sewage. In summary, this study found that the larval fish community can provide a biological means to trace water masses, and estimate their degree of mixing. Remarkably there was no significant effect of upwelling or sewage addition to the abundance or diversity of larval fish, in the nutrient poor waters of the East Australian Current. Larval carangids and pilchards were abundant in late spring off northern NSW, and their early life histories were inferred. Both larval carangid species seem to be spawned in the EAC waters, but as post-flexion larvae grew faster in the upwelled zone. Pre-flexion (less than 10 day old) larval carangids of both genera indicated spawning in the EAC, and the rarer post-flexion (greater than 10 days old) carangids grew faster in the upwelled waters. Here, both genera had stable isotope signatures characteristic of upwelled waters for carbon, but had different nitrogen signatures, indicative of different diets and trophic level status. Larval pilchards actually grew more slowly in the upwelling region, as observed in coastal waters off Japan, and their nursery grounds may be further offshore in the Tasman Front, analogous to their early life history in the Kuroshio Extension.
17
Martin, Jose Manuel Vergara. "Studies on the utilization of dietary protein and energy by gilthead sea bream (Sparus aurata L.)." Thesis, University of Stirling, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317614.
Full text
18
Mattsson, Emma. "Importance of Fucus vesiculosus (bladderwrack) for coastal fish communities in the Baltic Sea." Thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-176300.
Full textAbstract:
Within temperate coastal seascapes, macroalgae provide habitats for different organisms such as invertebrates and fish. In analogy to seagrass meadows, macroalgae beds are known for their importance as fish nurseries. However, within the Baltic Sea the importance of the canopy forming macroalgae Fucus vesiculosus for coastal fish communities, especially the juveniles, is unclear. In order to address this knowledge gap, fish communities in areas with and without F. vesiculosus were investigated around Askö, an island in the archipelago of the Baltic Sea. Sites were subjected to different exposures (sheltered, exposed or very exposed) and three different methods were used for sampling (underwater visual census (UVCs), beach seine netting and remote underwater videos (RUVs)). Overall, fish community composition differed significantly among locations and fish abundance and fish biomass were significantly higher in sites with F. vesiculosus than sites without. There was no significant relationship between algae cover or habitat complexity and fish abundance/biomass in sites with F. vesiculosus. Fish behaviour differed between sites with and without F. vesiculosus, with fish feeding more in sites with F. vesiculosus and traveling more in sites without F. vesiculosus. Only one location, Knabberskär, had significantly higher species richness in F. vesiculosus than in sites without F. vesiculosus. There were no differences in juvenile abundance among sites with or without F. vesiculosus and abundance of adult fish was higher than juvenile fish, regardless of location, site or species. Mean invertebrate abundance was a twice as high in the sheltered location Husbåtsviken than in Knabberskär. Higher fish abundance, fish biomass and species richness in sites with F. vesiculosus compared to sites without, suggest that macroalgae may play an important role in the Baltic Sea, however it might not be as important for juvenile fishes as predicted. The three different sampling methods provided similar results for fish abundance, but not for fish biomass. Continued studies where the relationship between fish communities and aspects of F. vesiculosus structure (such as canopy height) as well as linkage with other habitats is recommended for further understanding and better protection of F. vesiculosus habitats.
19
Al-Ameeri, A.-A. "Protein intake, ammonia excretion and growth of Oreochromis spilurus in sea water." Thesis, University of Stirling, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233795.
Full text
20
Greig, Antonio Bernardo. "The potential application of acoustic methods in North Sea demersal fish stock surveys." Thesis, University of Aberdeen, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485677.
Full textAbstract:
In the North Sea, groundfish stock assessment relies on independent bottom trawl surveys to tune the annual indices that are estimated from commercial landings. These surveys have been carried out by several European fishery institutions since the mid 19605 under standardized protocols which have allowed a long time series to be built for the main commercial stocks. An echo-integration survey is an independent metliod with a high ' sampling rate that can be carried out underway. Although it is successfully used on some stocks in the Barents Sea and off the North American Pacific coast, this method is not commonly used for demersal fish quantification. This study investigates the use of echointegration data, gathered during regular bottom trawl surveys in the North Sea~ in providing tuning indices for commercial stocks. To do this, density values extracted from bottom following layers in the acoustic dat{and partitioned by the corresponding catch proportions were compared to the density values obtained from the bottom trawl catches. Univariate and multivariate linear models including depth, position and time of day were fitted and showed very low correlation for demersal species, while resulting in reasonable to good correlation for aggregating pelagic species. As the acoustic method has a dead zone next to the seabed, an analysis of the dead zone dimensions in the study area as well as its mitigation was performed and a software routine was developed to optimize the data USge close to the seabed. A different approach, which allocated acoustic backscatter to targets according to visual interpretation of the echograms and scrutiny protocols, was performed on the optimized data and the density values compared to those of the catches. Correlation results did. not show significant improvement; however the scrutiny process revealed that demersal species were not evident on the echograms, irrespective ofthe catch in the bottom trawl. It is concluded that this discrepancy is due to the aggregation patterns in groundfish, and not necessarily the dead zone alone. Quantification of pelagic species can benefit from the use of echo-integration during bottom trawl surveys, however modifications to the survey design to allow targeted trawls and a systematic survey track are suggested to improve future studies.
21
Axenrot, Thomas. "Pelagic Fish Distribution and Dynamics in Coastal Areas in the Baltic Sea Proper." Doctoral thesis, Stockholm : Dept. of Systems Ecology, Univ, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-442.
Full text
22
Curtis, Janelle Marie Renelle. "Life history, ecology and conservation of European seahorses." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85146.
Full textAbstract:
My thesis examined the implications of life history and ecology for population-level responses of the European long-snouted seahorse ( Hippocampus guttulatus Cuvier 1829) to habitat alteration, exploitation and a recommended minimum size limit for seahorse management. The research employed a mark-recapture study, underwater visual censuses (UVCs) and catch data from an unrelated experimental sampling program in the Ria Formosa Lagoon (southern Portugal). These small-bodied fish are characterized by rapid growth rate, early age at maturity, high natural mortality, short generation time, short life span and multiple spawnings per year, traits that are usually associated with resilience to exploitation. However specialized parental care, complex social interactions, small adult home ranges and benthic habit confer risk to H. guttulatus. Population-level responses to experimental reductions in non-selective fishing effort differed in magnitude and direction between H. guttulatus and its smaller congener, Hippocampus hippocampus: the abundance of H. guttulatus increased significantly while its congener decreased in abundance. Hippocampus guttulatus preferred more complex, vegetated habitats, while H. hippocampus preferred more open, sparsely vegetated habitats. Thus it seems probable that H. guttulatus fared better in the more complex habitats that developed when seining stopped, whereas H. hippocampus fared better in the less complex habitat arising from repeated seining. I used an age-structured stochastic simulation to evaluate the biological implications of a recommended generic strategy (10 cm minimum size limit) for managing the exploitation and international trade of seahorses, using H. guttulatus as a model. The smallest size limit that was robust (using the magnitude of population decline and probability of quasi-extinction as criteria) to a range of fishing rates, maximum population growth rates (rmax) and models of density-dependence
23
Marohn, Lasse [Verfasser]. "Microchemical analyses of otoliths in Baltic Sea fish : Possibilities and limitations of otolith elemental analysis to describe individual life history and stock characteristics of fish in the Baltic Sea / Lasse Marohn." Kiel : Universitätsbibliothek Kiel, 2011. http://d-nb.info/1020244720/34.
Full text
24
Hedberg, Nils. "Sea cages, seaweeds and seascapes : Causes and consequences of spatial links between aquaculture and ecosystems." Doctoral thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-141009.
Full textAbstract:
Aquaculture is of growing importance in the global seafood production. The environmental impact of aquaculture will largely depend on the type of environment in which the aquaculture system is placed. Sometimes, due to the abiotic or biotic conditions of the seascape, certain aquaculture systems tend to be placed within or near specific ecosystems, a phenomenon that in this thesis is referred to as aquaculture system - ecosystem links. The exposed ecosystems can be more or less sensitive to the system specific impacts. Some links are known to be widespread and especially hazardous for the subjected ecosystem such as the one between the shrimp aquaculture and the mangrove forest ecosystem. The aim of this thesis was to identify and investigate causes and consequences of other spatial links between aquaculture and ecosystems in the tropical seascape. Two different aquaculture system - ecosystem links were identified by using high resolution satellite maps and coastal habitat maps; the link between sea cage aquaculture and coral reefs, and the one between seaweed farms and seagrass beds. This was followed by interviews with the sea cage- and seaweed farmers to find the drivers behind the farm site selection. Many seaweed farmers actively choose to establish their farms on sea grass beds but sea cage farmers did not consider coral reefs when choosing location for their farms. The investigated environmental consequences of the spatial link between sea cage aquaculture and coral reefs were considerable both on the local coral reef structure, and coral associated bacterial community. Furthermore, coral reef associated fish are used as seedlings and feed on the farms, which likely alter the coral food web and lower the ecosystem resilience. Unregulated use of last resort antibiotics in both fish- and lobster farms were also found to be a wide spread practice within the sea cage aquaculture system, suggesting a high risk for development of antibiotic resistant bacteria. The effects of seaweed farms on seagrass beds were not studied in this thesis but have earlier been shown to be rather substantial within the borders of the farm but less so outside the farm. Further, a nomenclature is presented to facilitate the discussion about production system - ecosystem links, which may also be used to be able to incorporate the landscape level within eco-certifying schemes or environmental risk assessments. Finally - increased awareness of the mechanisms that link specific aquaculture to specific habitats, would improve management practices and increase sustainability of an important and still growing food producing sector - the marine aquaculture.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.
25
Gonçalves, Ana Patrícia Cordeiro. "Effects of polymeric nanoparticles on fish : a multiparametric approach." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/21473.
Full textAbstract:
Mestrado em Biologia Molecular e CelularThe contamination of aquatic systems with several kinds of debris is an emerging environmental crisis. One of the problems associated with plastic pollution is its persistence. Plastic particles do not disappear, they slowly degraded from macro to micro to nano sizes. Although an increasing number of studies are currently assessing the effects of microplastics in aquatic organisms, the effects or nanoplastics are largely unknown. The present study aims to assess the short-term effects of polymeric nanoparticles in fish alone and in the presence of organic matter. Thus, the effects on ontogenic development were assessed in Danio rerio, a freshwater fish, by exposing fish embryos for 96h to PMMA (concentration range from 2.5 to 202.5 mg/L) and PS (concentration range from 2.5 to 1822.5 mg/L) particles (≈ 50 nm). In addition to ontogenic development, behavioural (distance and time swam as well as thigmotaxis) and biochemical effects (NPT, CAT, GPx, GST, GR and LPO) were also assessed. Effects on Dicentrarchus labrax, a marine fish species, were also assessed after 96h exposure. Assessed parameters included genotoxicity (erythrocytes micronuclei and other nuclear abnormalities and echinocytes shape differences) and effects on antioxidant status and damage (NPT, CAT, GPx, GST, GR and LPO). Overall, the nanoparticles revealed ability to be pernicious to fish, with PMMA presenting a higher toxicity to fish than PS. D. rerio displayed behavioural alterations associated with overall activity and stress responses. In D. labrax, the tested nanoparticles were genotoxic, as demonstrated by the increase of erythrocytes nuclear abnormalities. the assessed biochemical responses were more responsive in gills and liver than intestine with data confirming that nanoplastics have the ability to affect antioxidant status. The present study results are highly relevant as they demonstrate the ability of the tested nanoplastics to affect fish development and behaviour and that they are cytogenotoxic.
A contaminação de sistemas aquáticos com vários tipos de detritos é uma crise ambiental emergente. Um dos problemas associados à poluição com plásticos é a sua persistência. As partículas de plástico não desaparecem, degradaram lentamente de tamanhos macro para micro para nano. Embora atualmente haja um número crescente de estudos que avaliem os efeitos dos microplásticos em organismos aquáticos, os efeitos de nanoplásticos são amplamente desconhecidos. O presente estudo tem como objetivo avaliar os efeitos a curto prazo das nanopartículas poliméricas em peixes e na presença de matéria orgânica. Assim, os efeitos sobre o desenvolvimento ontogénico foram avaliados em Danio rerio, um peixe de água doce, expondo embriões de peixe por 96h a PMMA (intervalo de concentração de 2,5 a 202,5 mg/L) e PS (intervalo de concentração de 2,5 a 1822,5 mg/L) de partículas (≈ 50 nm). Além do desenvolvimento ontogénico, foram também avaliados efeitos comportamentais (distância e tempo de natação, assim como o tigmotaxia) e os efeitos bioquímicos (NPT, CAT, GPx, GST, GR e LPO). Efeitos no Dicentrarchus labrax, uma espécie de peixe marinho, também foram avaliados após a exposição de 96h. Os parâmetros avaliados incluíram genotoxicidade (micronúcleos de eritrócitos e outras anormalidades nucleares e diferenças de forma de equinócitos) e efeitos sobre o estado e dano antioxidante (NPT, CAT, GPx, GST, GR e LPO). No geral, as nanopartículas revelaram a capacidade de ser perniciosas para peixes, com PMMA apresentando maior toxicidade para o peixe do que o PS. D. rerio apresentou alterações comportamentais associadas à atividade geral e respostas de stress. Em D. labrax, as nanopartículas testadas foram genotóxicas, como demonstrado pelo aumento das anormalidades nucleares dos eritrócitos. As respostas bioquímicas avaliadas foram mais sensíveis nas brânquias e no fígado do que no intestino, com dados que confirmam que os nanoplásticos têm a capacidade de afetar o estado antioxidante. Os resultados do presente estudo são altamente relevantes, pois demonstram a capacidade dos nanoplásticos testados para afetar o desenvolvimento e o comportamento dos peixes e que eles são citogenotóxicos.
26
Jones, Emma G. "'Burial at sea' : consumption and dispersal of large fish and cetacean food-falls by deep-sea scavengers in the abyssal Northeast Atlantic Ocean and Eastern Mediterranean Sea." Thesis, University of Aberdeen, 1999. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU484683.
Full textAbstract:
The fate of cetacean carcasses in the deep-sea was investigated using autonomous lander vehicles incorporating time-lapse camera and acoustic tracking systems, as well as fish and amphipod traps. Four lander deployments placed cetacean carcasses at depths of 4000-4800m in the Northeast Atlantic for periods of 36h, 152h, 276h and 480h, before being recovered. The photographic sequences revealed that the soft tissue of carcasses was consumed at rates varying from 0.05-0.48kg.h-1, depending on how intact the carcass was. In each deployment, approximately 1h after emplacement, the grenadier Coryphaenoides (Nematonurus) armatus and large numbers of lysianassid amphipods had arrived at the food-fall. Amphipods appeared to be the only scavengers able to feed directly on the carcass. They tunnelled through the skin and connective tissue layer to reach the blubber and muscle, which was consumed in preference to anything else. Despite being unable to feed on the carcass directly, grenadier numbers remained high until the majority of the bait had been consumed. They were believed to be preying on amphipods attracted to the food-fall. Acoustic tracking studies suggested that, although overall fish numbers remained high during this phase, individuals did not stay significantly longer at the site of the large food-fall compared to a small one, and a "conveyer-belt" of fish arrived, fed and dispersed on a scale of 10s to 100s of km. Once the soft tissue had been removed, grenadier numbers declined and mobile scavengers were replaced by a variety of more benthic fish and invertebrates, some of which took up residence amongst the bones, e.g. eelpouts and galtheid crabs. Funnel traps recovered with the carcass and from a series of fish trap deployments of varying duration indicated a succession in species composition of amphipods, with specialist necrophages such as Eurythenes gryllus and Paralicella sp. being replaced by more generalist feeders of the Orchomene species complex.
27
Holmborn, Towe. "Zooplankton growth and trophic linkages : Implications for fish feeding conditions in the Baltic Sea." Doctoral thesis, Stockholms universitet, Systemekologiska institutionen, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-29485.
Full textAbstract:
The aim of this Thesis was to improve our understanding and assessment of feeding conditions for zooplanktivorous fish in the Baltic Sea. We investigated (papers I, II) the usefulness of biochemical proxies for assessments of growth and metabolic rates in the dominant Baltic copepod Acartia bifilosa. A predictive model (paper I) for egg production rate (EPR), based on body size, RNA content, and water temperature, was established using females of different geographical origin. This model demonstrates the usefulness of RNA content as a proxy for growth in zooplankton and, together with abundance data, it could be used to evaluate fish feeding conditions. Further (paper II), using A. bifilosa exposed to a food gradient, we evaluated responses of physiological rates and other biochemical proxies for growth and established correlations between physiological and biochemical variables. EPR and ingestion rate were most significantly correlated with RNA content. As assayed variables saturated at different food concentrations, food availability may affect assessments of physiological rates using proxies. In paper III, we explored the effect of high EPR and ingestion rate on astaxanthin content in A. bifilosa. We found that the astaxanthin content decreased at high feeding rates, most likely due to decreased assimilation efficiency. This may impact the quality of zooplankton as prey. The invasion of Cercopagis pengoi, a zooplanktivorous cladoceran, has altered the trophic linkages in the Baltic Sea food web. In paper IV, we evaluated the feeding of zooplanktivorous fish on C. pengoi and found that irrespective of size both herring and sprat feed on it, with large herring being more selective. In turn, C. pengoi feeds mainly on older copepods (paper V), which are acknowledged important in fish nutrition. These results indicate that C. pengoi may compete with fish due to the diet overlap.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In progress. Paper 3: Submitted
28
Cole, Russell Gavin. "Distributional relationships among subtidal algae, sea urchins and reef fish in northeastern New Zealand." Thesis, University of Auckland, 1993. http://hdl.handle.net/2292/1912.
Full textAbstract:
Interactions among large brown macroalgae, sea urchins, and fishes were investigated in northeastern New Zealand during the period 1988 - 1993. The Cape Rodney to Okakari Point Marine Reserve was the site of many of these investigations. The patterns of abundance of large brown macroalgae and urchins down depth gradients over a wide geographic range were compared with those reported from earlier studies, and 3 major trends were identified. First, the fucoid alga Carpophyllum flexuosum now occurs at many sites which are exposed to wave action, in contrast to earlier studies. This alga occurred most abundantly on urchin-grazed coralline flat areas. Second, at four sites in the Marine Reserve, the densities of the echinometrid urchin Evechinus chloroticus decreased with increasing depth, rather than reaching maximal densities at mid-depths, as had previously been described. Finally, at sites of decreased exposure to wave action, the coralline flats habitat did not occur at all, and dense stands of. C. flexuosum occurred, in conjunction with the ubiquitous laminarian alga, Ecklonia radiata. Following the discovery of this new algal component to exposed rocky reefs, a more detailed study of its population characteristics was initiated. The population size structure of C. flexuosum on coralline flat areas was markedly different from that of the same species in sites sheltered from wave action. These differences occurred at both offshore islands and sites near Leigh, suggesting that it was a general pattern. C. flexuosum plants on coralline flats were smaller than those from sheltered sites, and had a greater number of smaller laminae, heavier stipes, and a greater degree of branching. There was some evidence of temporal change in the morphology of C. flexuosum from coralline flats. Comparisons between a site with C. flexuosum and a site with coralline flats suggested that the activity of fish was 75% lower in the vegetated than in the unvegetated site, and the feeding rate in the vegetated site was less than 50% that in the unvegetated site. I speculate that future effects on fish activity of the invasion of C. flexuosum into a habitat which previously lacked macroalgal vegetation may depend on changes in the morphology of plants. An investigation of many aspects of the biology of E. chloroticus in different habitats was undertaken. Analysis of the body dimensions of E. chloroticus suggested that this species was relatively tall compared to other echinometrids (average ratio of test height: test diameter = 0.54), Comparisons among habitats with differing amounts of vegetation revealed only small differences in the relationship between test diameter and test height. Small E. chloroticus (<40 mm test diameter) lived in crevices, while larger individuals grazed freely over the substratum. In vegetated habitats, the crevice-dwelling habit was maintained at test diameters about l0 mm greater than in unvegetated habitats. Very small (<20 mm test diameter) E. chloroticus frequently covered themselves with shell. Population size structures of E. chloroticus within the Cape Rodney to Okakari Point Marine Reserve were bimodal; other localities had unimodal populations. Modal sizes varied among localities, with smallest modes (50-60 mm TD) being found at Inner Hauraki Gulf sites, and largest modes at the offshore Mokohinau Islands (70-80 mm TD). Habitat did not predictably affect population size structure. A bimodal population structure was maintained at Waterfall Reef rock flats throughout the 5-year study period. Gonad size showed seasonal fluctuations at several sites, being greatest in summer. There were few consistent differences in gonad size between biological habitats. Gonad colour varied among sites and habitats, with orange gonads generally being more prevalent in vegetated habitats, and black gonads being represented more in unvegetated habitats. Smaller urchins had greater proportions of orange gonads, while larger urchins had greater proportions of brown and black gonads. Although highly variable among individual urchins, movement of E. chloroticus was greater at unvegetated sites (0.7 m per 5 days) than at vegetated sites (0.4 m per 5 days), in the Marine Reserve. Feeding of E. chloroticus was studied at a number of sites in the Marine Reserve. Urchins frequently consumed drift algae, particularly E. radiata. C. flexuosum was consumed at less than half the rate of other macroalgae in several laboratory feeding experiments, and was chosen least frequently in a field assay of feeding preferences among 8 species of macroalgae. Boosting densities of E. chloroticus in stands of E. radiata to 60 m-2 led to destructive grazing of plants over a 2 month period - at lower densities, the urchins dispersed. Densities of C. flexuosum were effectively unchanged when urchin densities were increased to these elevated levels. As a result of these observations I speculate that feeding preferences of E. chloroticus may have a role in allowing C. flexuosum to survive on coralline flats. In a laboratory experiment, urchins from a feeding aggregation did not graze algae at higher rates than individuals from outside aggregations. Diets of both E. radiata and C. flexuosum consistently produced similar gonad volumes in urchins held in the laboratory, although gonad volumes produced were low. A preliminary experiment suggested that C. flexuosum from exposed sites was consumed at lower rates than C. flexuosum from sites which were sheltered from wave action. These differences in palatability are mirrored in the formation of stable borders between coralline flats and C. flexuosum of the sheltered morphology, and the ability of C. flexuosum of the exposed morphology to survive in the coralline flats habitat. The fish fauna of the Cape Rodney to Okakari Point Marine Reserve was shown to be different from that of a nearby area. A number of species were more abundant within the Marine Reserve. Subsequent surveys showed that there were differences in abundances of 3 large carnivorous fishes among sites within the Marine Reserve, and that population size structure and the distance within which divers could approach one species, (Pagrus auratus), clearly varied between areas within the Marine Reserve. Mean standard length of P. auratus in the central marine reserve was 40% larger than that of P. auratus outside the central marine reserve, and the average minimum approach distance was 70% less in the central marine reserve. Feeding of fish by humans in the central part of the Marine Reserve was suggested to be the main cause of the differences in responses to divers. Population size structure of, and crevice occupancy by, E. chloroticus, clearly differed between the Marine Reserve and an adjacent area, with bimodal population size structures and a 10 mm greater size of crevice occupancy occurring in the Marine Reserve. The implications of these findings for extrapolating from experiments done in one area to other areas are discussed. The major biological components of rocky reef habitats identified in this study were broadly similar to those identified in previous studies in northeastern New Zealand, and have parallels in overseas studies. Long term changes to the flora of rocky reefs in northeastern New Zealand have occurred, and appear to persist by a mechanism which had previously been discounted. Similar processes to those observed in overseas studies appear to maintain habitats (consistent recruitment of algae or urchins to habitats which they dominate), or cause them to change from one habitat state to another (e.g. grazing outbreaks by urchins). However, the predictability of the persistence of these habitats at a particular site appears to be low. Further, the precise mechanisms whereby habitats may change from one to another may also be unpredictable. I argue that there is little scope for general statements concerning the spatial and temporal occurrence, or mode, of habitat transitions on temperate subtidal reefs. This study emphasises the value of repeated descriptions of patterns of abundance, and highlights problems of extrapolation and generalisation in marine ecology. Insufficient information exists at present to comment adequately on the persistence of subtidal habitat types. This may in part stem from the types of information which have been collected in the past. Methodological problems with the use of quadrats to sample densities of organisms in areas of differing topography are therefore addressed. In conclusion, it is suggested that sampling protocols which incorporate a variety of information, gathered over as wide an area, and as intensively as possible, should be used in future research of this type.
29
Bobsien, Ivo Christian. "The role of small fish species in eelgrass food webs of the Baltic Sea." kostenfrei, 2006. http://e-diss.uni-kiel.de/diss_1703/d1703.pdf.
Full text
30
Kazic, Amra. "The utility of molecular genetic analysis of museum specimens in study deep-sea fish." Thesis, Open University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489900.
Full textAbstract:
The damaging effect of formalin on DNA and the inhibition of PCR are serious problems in molecular studies. The aims of the project were to investigate the possibility of using formalin-fixed, Steedman's preserved museum specimens in molecular investigations, especially organisms with unstudied genomes. A number of DNA extraction protocols and different pre-washing/drying regimes were tested.
31
Okuda, Noboru. "Life history and sexual strategies of the cardinal fish (Pisces:Apogonidae) in the temperate sea." 京都大学 (Kyoto University), 1997. http://hdl.handle.net/2433/86473.
Full text
32
Seyhan, Kadir. "Gastric emptying, food consumption and ecological impact of whiting, Merlangius merlangus (L.) in the eastern Irish Sea marine ecosystem." Thesis, Bangor University, 1994. http://e.bangor.ac.uk/4295/.
Full textAbstract:
Gastric emptying of Sprattus sprattus and Arenicola spp. (gastric lavage) and formulated pellets (X-Ray studies) was investigated in a range of sizes of whiting, Merlangius merlangus fed different meal sizes at different temperatures. Emptying of indigestible solids, barium sulphate spheroids and ballotini were also studied. Additionally stomach contents of whiting sampled from Red Wharf Bay, Eastern Anglesey, UK. were analysed to determine diet composition, diel feeding periodicity and feeding strategy of whiting. Daily and total annual intake of main prey taxa, sprat, sandeel and crab, were estimated. Finally feeding behaviour of whiting in captivity was monitored. With respect to the studies conducted under laboratory conditions, it was found that gastric emptying is best described by a linear function. The results indicated significant changes in gastric emptying rates with both prey type and size. The seasonal change in temperature did not yield a significant change in gastric emptying rate. Increase in diet surface area also did not alter the gastric emptying rate significantly. The results have also shown that in continuously- feeding whiting gastric emptying is affected by the second meal such that the arrival of the second meal is accompanied by rapid emptying of a small fraction of the first meal. Despite difficulties encountered with individual variation among whiting of similar size held under similar conditions, gastric emptying times (GET) for both natural food and formulated pellets can be adequately predicted by the equations: GET = 126.47 W -0.111 g 0.26 e -0.068T for the natural food, GET = 6.6 e -0.09T + 2.48 W0.566 e -0.044T for the formulated pellets; where W is the fish weight (g), S is the meal size (g) and T is the temperature (°C) suggesting that a similar meal size of formulated pellet is emptied faster than natural food, Sprattus sprattus. This was interpreted as evidence that natural diets may reflect a combination of 2 factors (a) the relative size of stimulation to the stomach (% distension) and (b) the existence of protective, fibrous skin which resists digestion. Barium sulphate spheroids of diameter 1 mm (ca 20 per g food) and ballotini of diameter 0.029- 0.049 mm (60-100 per 1.58g) were selectively retained by the whiting stomach, suggesting that these indigestible materials can not be used in gastric emptying studies in whiting. Under laboratory conditions with continuous food availability, medium size whiting (155.25±27.98 g) consumed 5.29 g sprat corresponding to 3.41 %bw (approximately 3 sprat, 1.88g each) at 14 °C. The return of appetite after a single meal was found to follow the gastric emptying curve closely. However if food is not offered directly, but made available through demand feeding, the whiting feed rhythmically (every 21 hours), under these conditions it was estimated that feeding activity returns when the stomach is 40 % full. It wa§ found that, in the wild, whiting prefer fish (Sprattus sprattus and Ammodytes spp. ) and crustaceans and only turn to the polychaetes as a third option, even when they are readily available, when preferred food is scarce. The availability of prey was found to be the main criterion in whiting feeding strategy. In March fish were dominant for most whiting, in August and September/October however, Liocarcinus spp. and Corystes cassivelaunus were the main prey items found in whiting stomach reflecting the availability of these prey species. A highly correlated relationship was found between predator (whiting) and prey (sandeel) length, however this was not noticed for sprat; whiting prey on sprat regardless of its length. An increase in feeding intensity was observed in the morning (August), in the evening (September/October), or at both times, crepuscular feeding pattern, (March). However, when feeding behaviour was investigated under laboratory conditions it was found that whiting is mainly a day time feeder with a slight increase in the morning and in the evening, but some feeding also occurs at night. Additionally a strong tendency was found for crustaceans to be found in fish captured during the daylight hours and fish at night in August and September/October. A linear model to estimate food consumption from the field samples was developed. F= (S2-S1) + 1.5 K T, where S2 and SI are average stomach contents at time tI and t2, K is the gastric emptying rate (gh-1) and T is temperature (°C). The average recruited whiting stock in the area of approximately 150 km2 in Red Wharf Bay was estimated to be 129,000 with a total biomass of 22 tonnes. It was estimated that young whiting (groups 0+ to 3+ years) in Red Wharf Bay eat between 1.29 and 6.57 g day-1 in February. By August, when temperature has maximised, these values increase by approximately 70-80 %. Daily intake of sprat, sandeel and crab was estimated to be 0.41,0.14 and 0.14 g for the 0+ group. This was increased to 0.70,0.80 and 0.94 g by the age of 4. On a daily basis the long-term average of the amount of sprat, sandeel and crab consumed were estimated to be 820, 370 and 520 g/km2/day respectively. Total food consumption per year by the recruited whiting stock in the area studied however was 44.8 tonnes of sprat (approximately 11.5 million sprats), 20 tonnes of sandeel and 28.5 tonnes of crab. These figures were compared with the available data from the North Sea as well as from other parts of the Irish Sea and it was concluded that whiting in the Irish Sea eat more than they do in the North Sea.
33
Ntiba, Micheni J. "The biology and ecology of the long rough dab, Hippoglossoides platessoides (Fabricius 1780) in the North Sea." Thesis, University of East Anglia, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328557.
Full text
34
Dean, Susan. "Tracking sea lice : Lepeophtheirus salmonis, between host fish populations using stable carbon and nitrogen isotopes." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31433.
Full textAbstract:
This study was undertaken to assess the use of carbon and nitrogen stable isotope
analyses as methods to identify source host fish populations of sea lice, Lepeophtheirus
salmonis. The delta carbon signatures of parasitic copepodid sea lice used to infect
cultured Atlantic salmon in the laboratory were found to be statistically indistinguishable
from the delta carbon signatures of blood (ANOVA, p = 1.000) and mucus (ANOVA, p =
0.430) sampled from the wild pink salmon population from which the sea lice originated.
As a result, delta carbon signatures show potential as tools to track the movement of sea
lice between fish populations. In contrast, delta nitrogen analysis did not show such
promise as the natal host fish, wild pink salmon, and novel host fish, cultured Atlantic
salmon, between which sea lice were transferred during the study, did not display distinct
isotope signatures and thus could not be differentiated. This study found that when
applying stable isotope analysis as a method to studying the dispersal of sea lice (1) the
blood and mucus of potential source host fish populations should be sampled when
assessing their possible relationship to sampled sea lice, (2) sea lice in no later than the
parasitic copepodid stage should be analysed, (3) sea lice should be given time to clear
their guts of any host materials before analysis takes place, (4) sea lice sampled from the
gills should not be not grouped with sea lice sampled from the body surface or fins, and
(5) replication unit for sampled parasitic copepodids should be set at the individual and
not host fish level. The application of stable carbon isotopes to tracking the movement of
sea lice between host fish is a promising method for directly identifying sources of sea
lice epizootics and of quantifying the exchange of sea lice between host fish populations.Land and Food Systems, Faculty of
Graduate
35
Smith, Alastair. "On brain, behaviour and biochemistry of the deep-sea demersal grenadier fish, Coryphaenoides (Nematonurus) armatus." Thesis, University of Aberdeen, 1996. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU089956.
Full textAbstract:
In surface-dwelling vertebrates, pineal melatonin is secreted in a manner directly related to photoperiod. Despite an absence of solar light, several deep-water fishes show some seasonality. The presence of central melatonin receptors was investigated using in vitro autoradiography in the deep-sea fish Coryphaenoides (Nematonurus ) armatus. No specific 2-[125I]iodomelatonin (IMEL) binding was found in optic tectum, cerebellum or hypothalamus. Specific binding was however found over mid-brain tegmentum and hindbrain. Two possible cues in the deep-sea are seasonal depositions of phytodetritus and diurnal/semidiurnal currents. Both gustatory and acousticolateralis systems are well developed and capable of detecting such cues. The principle sites of specific IMEL binding are regions which integrate inputs from these non-optic senses. The behaviour of deep-sea scavenging fishes was investigated using a baited free-fall photographic and fish tracking system - AUDOS (Aberdeen University Deep Ocean System). Data collected during spring (April, 1994) at 4800m depth, NE Atlantic were compared with previous studies at the same location during summer, 1989. The time and species of first arrivals and mean staying time showed no differences between years or season. However, radial swimming speed (0.009 m.s-1) of C.(N) armatus was significantly slower than in previous studies. A change in size distribution to smaller individuals in spring 1994, might also suggest C.(N) armatus may undertake major episodic or seasonal migrations. The white muscle protein content of deep-water fishes is about 40% lower than in shallow-water species. This appears to be accompanied by lower numbers of ribosomes. Any increase in RNA content to compensate for low efficiency at low temperatures is not apparent and may be due to reductions caused by other factors.
36
Acebes, Jo Marie. "Hunting “Big Fish”: A marine environmental history of a contested fishery in the Bohol Sea." Thesis, Acebes, Jo Marie (2013) Hunting “Big Fish”: A marine environmental history of a contested fishery in the Bohol Sea. PhD thesis, Murdoch University, 2013. https://researchrepository.murdoch.edu.au/id/eprint/28259/.
Full textAbstract:
The Bohol Sea in the Philippines has a high biodiversity of large marine vertebrates. It is also one of the primary fishing grounds in the Central Visayas. This is a study of the history of interactions of the fishers of the Bohol Sea with the ‘big fishes’ living within it. These ‘big fishes’ are the large marine vertebrates, namely whales, dolphins, whale sharks and manta rays. It is the story of the changes in the Bohol Sea and how the communities who depended on it affected these changes. Similarly, it discusses how the Bohol Sea and the large marine vertebrates shaped the lives of the coastal peoples living around it. This study aims to determine the extent of the fisheries for whales, dolphins, whale sharks and manta rays in the Bohol Sea from the 19th century to recent times. It focuses on the fishing communities of southern Bohol, Camiguin and Southern Leyte in the Central Visayas, who are known to hunt these large marine vertebrates, and aims to describe the characteristics and trace the evolution of these fisheries. Through a multidisciplinary approach, this study uses a combination of ethnographic and historical research methods, together with biological data, from published and unpublished sources. The study aims to determine if the abundance and distribution of large marine vertebrates in the Bohol Sea changed in the long-term. It also examines how the fishing communities adapted to the ecological, socio-economic and political changes over time.
From its beginnings in the late nineteenth century, the hunting of whales, dolphins, whale sharks and manta rays, in the different communities around the Bohol Sea underwent very similar and, for some, identical technological developments. These fishing technologies and patterns were adapted to the nature of their target species. By the late twentieth century, with increasing population, worsening economic conditions, and declining fish stocks in the country, the Bohol Sea fishing communities’ dependence on the fisheries for large marine vertebrates also increased. Likewise, fishery policies and legislative frameworks were also evolving with a more protectionist and conservationist stance. The implementation of fishery bans in the 1990s compelled most fishers to comply and adapt, however others resisted. Communities who lived in an environment endowed with more diverse and abundant resources proved to be more resilient. While those who heavily depended on the fishery and had little else to turn to have continued to hunt up to the present day. Despite continuing protests and public clamour for a total ban on hunting for all other species of rays in the Philippines, the ray fishery in the Bohol Sea continues.
This study demonstrates how state efforts to conserve whales, dolphins, whale sharks and manta rays in the Philippines have been ineffective. This is primarily because of the lack of legitimacy of these fishery policies in the eyes of the communities. This study also highlights the importance of using multiple and non-traditional data sources in evaluating fisheries that are data deficient. The study shows how it is important to examine the historical context of ecological and social systems in order to understand the causes of contemporary resource management problems.
37
Speckman, Suzann Gail. "Characterizing fish schools in relation to the marine environment and their use by seabirds in lower Cook Inlet, Alaska /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/5301.
Full text
38
Minghetti, Matteo. "Characterisation and expression of copper homeostasis genes in sea bream (Sparus aurata)." Thesis, University of Stirling, 2009. http://hdl.handle.net/1893/1113.
Full textAbstract:
The redox properties of Copper (Cu) make it both an ideal cofactor for many enzymes, and, in its free form, a highly toxic molecule capable of stimulating production of reactive oxygen species or binding to protein thiol groups. Therefore, living organisms have evolved homeostatic systems to “handle” Cu avoiding dangerous and wasteful aspecific interactions. These systems comprise uptake, carrier, storage and excretion proteins. The importance of Cu-homeostatic systems was initially discovered in humans where alterations of Cu-excretory proteins were shown to be responsible for two lethal genetic disorders; the Wilson and Menkes diseases. The levels of bioavailable Cu in the aquatic environment is important because concentrations in oceanic waters tend to be minute, whilst in some fresh and coastal waters, particularly around areas of mineral extraction, viniculture and farming operations, concentrations can be excessive. In contrast to terrestrial vertebrates, fish are not only exposed to dietary sources of copper but are also exposed to dissolved ionic copper that may enter via the skin and gills. Indeed, the latter route is important in fish and it has been demonstrated in physiological studies that under conditions of dietary deficiency, fish can satisfy their own body requirements by uptake from water. Therefore, fish must have systems relating to both gill and gut to enable maintenance of body homeostasis of this essential, yet toxic, metal. In an attempt to understand the mechanisms of Cu homeostasis in fish, whether under conditions of deficiency, adequacy or excess, it is essential to consider the expression of known Cu-homeostasis proteins. Thus, cDNAs for sea bream (Sparus aurata) homologues of copper transporter 1 (Ctr1), antioxidant protein 1 (Atox1), Menkes protein (ATP7A), Wilson protein (ATP7B), and metallothionein (MT), which are responsible for the uptake, delivery to the secretory pathway and scavenging of intracellular Cu, were cloned and their mRNA tissue expression levels measured. To investigate the molecular basis of the different homeostatic and toxic responses to waterborne or dietary Cu, sea bream were exposed to sub-toxic levels of Cu in the diet (130 mg/Kg of dry diet) or water (0.3 mg/L) and tissue mRNA and Cu levels were measured. Moreover, to discriminate between the effect of different metals on the transcriptional regulation of Cu homeostasis genes in fish, Sparus aurata fibroblast (SAF1) cells were exposed to sub-toxic levels of Cu (25 μM), Zn (100 μM) and Cd (10 μM). In addition, a microarray was used to gain a broader overview of the transcriptional response of SAF1 cells to Cu (25 μM). Waterborne or dietary Cu resulted in distinct expression profiles of Cu-homeostasis genes and markers of oxidative stress. After dietary exposure, Cu increased in intestine and liver, whilst after waterborne exposure Cu increased in gill and liver. Exposure to dietary Cu resulted in decreases in Ctr1 and ATP7A mRNA in both liver and intestine. Renal Ctr1 levels remained unchanged, whilst ATP7A mRNA decreased. In contrast, waterborne Cu exposure increased intestinal Ctr1 and ATP7A mRNA, and increased renal Ctr1 and decreased renal ATP7A mRNA. Both dietary and waterborne Cu increased ATP7B mRNA in liver. Metallothionein (MT) mRNA increased in liver and gill after waterborne Cu. Glutathione reductase (GR), a marker of oxidative stress, increased expression in liver and gill after waterborne Cu exposure, but decreased in intestine. Thus, exposure to Cu via water or diet has different, often opposite effects on Cu-homeostasis genes. The decrease in expression of both Cu-transport genes in intestine after dietary exposure may indicate a defensive mechanism to limit uptake of Cu. The opposite effects in intestine after waterborne exposure are more difficult to explain, but again may reflect a defence mechanism against excess bloodborne Cu coming from the gill. Since both dietary and waterborne Cu increased Cu levels in liver and increased hepatic ATP7B it is likely that well-characterised mammalian route of Cu excretion to bile is active in sea bream. However, only hepatic Cu derived from gill increased the expression of the stress markers MT and GR. This suggests that Cu is delivered to liver in a different form from gill as that from intestine, the intestinally derived pool being less toxic. Thus the increase in copper transport gene expression in intestine after gill exposure might be a mechanism to enable incorporation of excess bloodborne Cu into the intestinal pathway of Cu delivery to liver, thus minimizing toxicity. The in vitro exposure of SAF1 cells to Cu showed a similar response to liver of fish exposed to waterborne Cu indicating similar Cu availability and complexation. ATP7A mRNA levels were induced by Cu but not by Zn or Cd suggesting Cu-specific regulation. Conversely, MT and GR were induced by all metals tested. The transcriptomic analysis highlighted that the biological processes most significantly affected by Cu were secretion, protein trafficking and stress. Overall, these results show that in fish copper has distinct effects on tissue Cu transporter genes and oxidative stress depending on whether it is taken up via the gill or gut and that intestinal absorption may be required for normal uptake and metabolism of Cu, regardless of the route of uptake. Moreover, changes in mRNA levels indicate that Cu homeostasis genes, at least in fish, may be regulated at the transcriptional level. Although more work needs to be done to identify genes that are robust predictors of Cu toxicity, the microarray results presented here show a clear transcriptional fingerprint which may characterize Cu toxicity in fish.
39
Mitchell, Rebecca E. "Large scale influence of fishing, fish and habitat on sea urchin abundance on Fijian coral reefs." Thesis, University of Newcastle Upon Tyne, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401620.
Full text
40
Al-Habsi, Saoud. "Trophic relationships of a demersal fish assemblage in the Arabian Sea elucidated by stable isotope approaches." Thesis, University of Newcastle Upon Tyne, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432492.
Full text
41
Stockley, Bruce MacDonald. "Spatial and temporal population genetics of two commercially exploited deep-sea fish from the Azores Archipelago." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392699.
Full text
42
Buckman, Kate Lynn. "Biotic and abiotic interactions of deep-sea hydrothermal vent-endemic fish on the East Pacific Rise." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54566.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references.
A study of the ecology of fish endemic to hydrothermal vents on the East Pacific Rise was undertaken utilizing a variety of techniques, focusing on the bythitid Thermichthys hollisi. Stable isotope and gut content analyses were used to elucidate prey choice and trophic relationships. Otolith chemical signatures were investigated to determine whether this technique could be utilized to examine life history strategy and habitat use. Chemical characteristics of preferred fish habitat and gene expression responses habitat chemistry were explored. Gut contents indicated that T. hollisi specimens were actively feeding upon a combination of brachyuran crabs, Alvinocaris shrimp, polychaetes, and zoarcid fish with the majority of fish containing evidence of crustacean prey. Carbon, nitrogen, and sulfur stable isotopic measurements support a chemosynthetically based prey source and place T. hollisi in the uppermost trophic levels of vent communities. The influence of exposure to hydrothermal fluids was apparent in otoliths from both species of vent fish, most noticeably within the relatively elevated Sr:Ca and depleted Mg:Ca ratios. Otolith chemistry suggested that the zoarcid Thermarces cerberus experiences greater direct exposure to diffuse fluids than does T. hollisi, which is concurrent with apparent habitat preferences. Isotopic patterns across the span of the otolith suggested that T. cerberus spends its entire life within the vent system. In contrast, it appeared that T. hollisi exists outside of the influence of hydrothermal activity for some early portion of its life-cycle.
(cont.) Time-lapse photography and in situ electrochemistry indicated that T. hollisi are preferentially utilizing fish holes where there are elevated temperatures and sulfide levels, and variable oxygen levels in comparison to ambient bottom water. A fragment of Cu, Zn superoxide dismutase was successfully amplified from T. hollisi mRNA, but there were no differences in expression levels between tissue types or among individuals within the small sample examined. In general, it appears that T. hollisi is both influenced by and may exert a greater influence on hydrothermal vent communities to a greater degree than initially hypothesized.
by Kate Lynn Buckman.
Ph.D.
43
Rodger, Andrew Neil Sutherland. "Sea-based integrated multi-trophic aquaculture : investigation of a fish, bivalve and macroalgal co-culture system." Thesis, University of the Highlands and Islands, 2010. https://pure.uhi.ac.uk/portal/en/studentthesis/seabased-integrated-multitrophic-aquaculture(cf63b33d-c09c-449d-a501-215df54b9395).html.
Full textAbstract:
Sea-based integrated multi-trophic aquaculture (sIMTA) was explored as an amalgam of the processes of polyculture and biofiltration, with the primary objectives of improved aquaculture production efficiency and wastes remediation. The study established a coculture of Atlantic salmon (Salmo salar, L.), Pacific oyster (Crassostrea gigas, Thunberg) and sugar kelp (Saccharina latissima, L.), in Scotland, and explored their production in relation to the background environment, historical aquaculture production modes, regulation and resource-use. The field trials demonstrated the dominance of the ambient environment in regulating trophic linkage of co-cultures. Enhanced growth of the bivalve and macroalgal components, over reference cultures, was only observable when ambient nutrients were limiting or favoured food, i.e. phytoplankton, was scarce. Localised differences within and between sealoch systems were also observed to be of importance. The complex physical processes of particulate waste dispersion and dissolved nutrient diffusion were simulated using established models and field data drivers. This process illustrated the potential benefits of designing the integrated farm to optimise trophic linkages as well as considering the final fate of wastes. The application of sIMTA was explored within the current regulatory regime, illustrating what regulatory gains (statutory and non-statutory) might be possible on account of the process and how the products of integration, as studied, are likely to meet with few regulatory food safety constraints within a UK market. The scarcity of aquaculture resources, partly through inefficient use, was explored. sIMTA is presented as a method which could possibly alleviate some of these resource-use inefficiencies when ambient environment supports, and as such sIMTA is proposed to qualify for priority resource allocations, in the context of greater socio-economic advantage.
44
Skaring, Ida. "Selective serotonin reuptake inhibitors in the Baltic Sea region : The effects of SSRI on teleost fish." Thesis, Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-35727.
Full textAbstract:
Pharmaceuticals, enter the aquatic environments through sewage treatment plants and may affect fish. This examination paper is a literature study that focuses on Selective serotonin reuptake inhibitors, SSRIs, exposure and the impacts on teleosts in the Baltic Sea by assessment of peer-reviewed literature and material. Teleosts affected by exposure of these substances may demonstrate physiologically as well as behavioral alterations. These can be observed as alterations in aggression, boldness, mobility, growth, feeding rate or in endocrine processes. The potential of which SSRI may effect teleosts depends on the pH of the aquatic environment, temperature, other contaminants and the fat solubility of the substances. Some effects caused by SSRI exposure may elicit ecological impacts. These particularly concern changes and effects in terms of evasiveness, reproductive capacity and ability to find food as well as alterations of interspecificity. Even the balance between population density, individual fitness and by extension survival might be affected. Effects in interspecificity may potentially lead to local extinctions and changes in food webs. Furthermore, results demonstrated that when a substance is bioaccumulated and the teleosts are eaten by predators on higher trophic levels, marine ecosystems can also be affected. Moreover a conclusion could be drawn the level of concentration of SSRIs in the aquatic environment may be of less significance since teleosts have the potential to bioaccumulate SSRIs in tissue over time and in this sense concentrations may reach harmful levels that can cause physiological or behavioural alterations. Continuous studies should refer to chronic tests studies with focus on a field testing environment for understanding of natural conditions and exposure. Furthermore, studies on how ecosystems may be affected should be important to give an overview of the problem with SSRI exposure. As the Baltic Sea is a sensitive environment, studies should preferable be made on species living in this environment.
45
Mindel, Beth L. "Variation in the structure and function of deep-sea fish assemblages with depth and over time." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/13277/.
Full textAbstract:
The deep sea is the largest environment on Earth, but has remained relatively under-studied due to its inaccessibility. In recent years however, technological advances have increased our understanding of this globally important system. In this thesis, I add to this understanding by examining fish assemblage structure along the environmental gradient of the continental slope at depths of 300–2000 m and over a time period (1998–2014) following a reduction in fishing pressure from previous levels. I show that body size is an important factor in structuring deep-sea assemblages along a depth gradient and that it increases at least up to 1500 m. A new metric, fractional size, builds on our knowledge of size structure by accounting for both intra- and interspecific variation in body size and also increases with depth. The Large Fish Indicator, the slope of the biomass spectrum and fractional size have increased over time, signifying recovery of the size structure of deep-sea assemblages, but this increase is depth-dependent. I reveal other depth-related changes by linking morphological traits that relate to function, such as caudal fin aspect ratio and gape size, to the shifting dominance of feeding guilds and patterns in functional diversity. I show that despite the uniqueness of deep-sea ecosystems, the general macroecological pattern of increasing regional occupancy with increasing local abundance still applies. I incorporate the all-pervading importance of depth into these abundance–occupancy relationships by calculating occupancy based on depth distribution as well as spatial distribution. This thesis reveals some surprising characteristics of deep-sea assemblages, such as high biodiversity and the ability to recover from fishing pressure. It further highlights the importance of body size in the marine environment and of depth resolution in deep-sea ecology.
46
Penner, Johan. "Effect of temporal increases in prey fish abundance on individual growth rates of coastal piscivores." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-121854.
Full textAbstract:
Commercial fishing in the Baltic Sea has led to decrease in abundance of large predatory fish and as a result the predation pressure on smaller fish species has been reduced. Three-spined stickleback (Gasterosteus aculeatus) is among the species that have benefited from reduced predation pressure. Sticklebacks are a small fish species that spends its juvenile stage in coastal habitat and its adult stage in the open sea with a yearly migration from the sea to coastal habitat and lakes for spawning. Sticklebacks have been shown to have a negative effect on fry of coastal species, such as perch (Perca fluviatilis). Therefore an increase in stickleback abundance, as a consequence of reduced predation pressure, can potentially further reduce abundance of fry of coastal species, such as perch. On the other hand sticklebacks could be subject to predation from adult perch. This two-species interaction is studied in the perspective of general ecological IGP (intra guild predation) theory. In order to determine how the observed increase of three-spined sticklebacks negatively or positively affects the growth of different stages of perch, a time series of operculum bones from perch collected by the coastal monitoring program prior to the increase of sticklebacks and up until present was analyzed. Three areas along the Swedish coast showing increased stickleback abundance (Gaviksfjärden, Norrbyn and Holmön) were compared to areas that had no sticklebacks or only a small increase in abundance (Kinnbäcksfjärden, Råneåfjärden, Långvindsfjärden) prior and after the general increase in stickleback density. In addition to the growth analysis, a dietary analysis of perch was carried out in order to determine to what extent perch utilize sticklebacks as a food source. I found that there were significant differences in regard to perch growth between the two time periods; however there was no significant difference in growth between the control areas and the stickleback areas except for perch of medium size. Further, this difference in growth between the control and stickleback areas was present both before and after the stickleback increase and could therefore not be tied directly to stickleback increase. Consequently, results from a multiple regression showed that stickleback abundance was not able to significantly explain the observed changes in perch growth. The dietary analysis showed that larger and intermediate perch tend to consume sticklebacks as well as benthic fauna and other fish species while smaller perch tended to feed exclusively on smaller invertebrates. This study concluded that the increase in stickleback abundance had only a very weak effect on perch growth.
47
Ciannelli, Lorenzo. "Cross-scale analysis of the Pribilof Archipelago, southeast Bering Sea, with a focus on age-0 walleye pollock (Theragra chalcogramma) /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/5292.
Full text
48
Massari, Francesco. "Species identification of archived fish bones collected from the Mediterranean Sea 100 years ago using molecular techniques." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8085/.
Full textAbstract:
With the discovery that DNA can be successfully recovered from museum collections, a new source of genetic information has been provided to extend our comprehension of the evolutionary history of species. However, historical specimens are often mislabeled or report incorrect information of origin, thus accurate identification of specimens is essential. Due to the highly damaged nature of ancient DNA many pitfalls exist and particular precautions need to be considered in order to perform genetic analysis. In this study we analyze 208 historical remains of pelagic fishes collected in the beginning of the 20th century. Through the adaptation of existing protocols, usually applied to human remains, we manage to successfully retrieve valuable genetic material from almost all of the examined samples using a guanidine and silica column-based approach. The combined use of two mitochondrial markers cytochrome-oxidase-1(mtDNA COI) and Control Region (mtDNA CR), and the nuclear marker first internal transcriber space (ITS1) allowed us to identify the majority of the examined specimens using traditional PCR and Sanger sequencing techniques. The creation of primers capable of amplifying heavily degraded DNA have great potential for future uses, both in ancient and in modern investigation. The methodologies developed in this study can in fact be applied for other ancient fish specimens as well as cooked or canned samples.
49
Ahlbeck, Ida. "Living in a predation matrix : Studies on fish and their prey in a Baltic Sea coastal area." Doctoral thesis, Stockholms universitet, Systemekologiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-75238.
Full textAbstract:
This thesis was written within the framework of a biomanipulation project where young-of-the-year (YOY) pikeperch (Sander lucioperca) were stocked to a Baltic Sea bay to improve water quality through a top-down trophic cascade. The aim of my doctorial studies was however focused on a broader ecological question, namely predation (the main driving force in a biomanipulation). Hence, this thesis consists of four papers where we study the interactions between predator and prey using fish and zooplankton and how these interactions can be measured. In paper I we evaluated the performance of different diet analysis methods by individual based modelling and found that when having a nutritional gain perspective, mass based methods described diets best. Paper II investigated how the explorative, foraging and anti-predator behaviour of the YOY pikeperch used for stocking were affected by their rearing environment (pond vs. tank rearing). The more complex and varied environment in the semi-natural ponds seemed to promote a more flexible and active behaviour, better equipping young fish for survival in the wild. For paper III we studied the diel vertical migration in the six copepodite stages of the zooplankton Acartia spp. and Eurytemora affinis in relation to fish biomass, phytoplankton abundance and temperature. Both species migrated and in addition showed increased migration range with size within species, indicating evasion from visual predators. Paper IV addressed the movement of littoral Eurasian perch (Perca fluviatilis) via stable isotope signatures (13C and 15N) and body condition. We found clear indications of sedentarity and intra-habitat dietary differences. Interactions between predators and prey are complex and affected by both physiological and environmental characteristics as well as behavioural traits. The results in this thesis suggest that different species and even different life stages pursue different strategies to survive.At the time of doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 2: In press. Paper 4: Submitted.
50
Wilde, James D. "Analysis of a niche market for farm-raised black sea bass Centropristis striata in North Carolina." View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-3/wildej/jameswilde.pdf.
Full text