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Letteratura scientifica selezionata sul tema "Bycatches (fisheries)"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 29 luglio 2024

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Articoli di riviste sul tema "Bycatches (fisheries)"

T. Murray, Kimberly, Andrew J. Read e Andrew R. Solow. "The use of time/area closures to reduce bycatches of harbour porpoises: lessons from the Gulf of Maine sink gillnet fishery". J. Cetacean Res. Manage. 2, n. 2 (1 settembre 2000): 135–41. http://dx.doi.org/10.47536/jcrm.v2i2.497.

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In 1994, the United States National Marine Fisheries Service (NMFS) implemented a series of time/area closures for the Gulf of Maine sink gillnet fishery to reduce the bycatch of harbour porpoises (Phocoena phocoena). The present study evaluates the effectiveness of the Mid-Coast closure area, implemented during November 1994. Rates of porpoise bycatches are analysed prior to, during and after the closure. In addition, individual vessels are tracked and the spatial distribution of fishing effort examined to determine how fishermen responded to the closure. The highest bycatch rate occurred in September in the Mid-Coast region, well before the closure. During November, fishermen concentrated much of their effort adjacent to the closed area in unrestricted waters, where bycatch occurred. The Mid-Coast closure was not in place for a long enough period, nor was it large enough, to be effective in reducing bycatch rates of harbour porpoises. The failure of the Mid-Coast closure is attributed to temporal and spatial variation in patterns of bycatch rates, and to the displacement of fishing effort and porpoise bycatch outside the closed area.

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Lesage, Veronique, Joanne Keays, Samuel Turgeon e Sylvain Hurtubise. "Bycatch of harbour porpoises (Phocoena phocoena) in gillnet fisheries of the Estuary and Gulf of St. Lawrence, Canada, 2000-02". J. Cetacean Res. Manage. 8, n. 1 (8 marzo 2023): 67–78. http://dx.doi.org/10.47536/jcrm.v8i1.703.

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The incidental catch of harbour porpoises (Phocoena phocoena) in the gillnet fishery of the Estuary and Gulf of St. Lawrence, Canada, was examined using: (1) questionnaires mailed to fishermen inquiring about bycatches in 2000 and 2001 (n=2,277 or 44% of the fishermen with valid licenses); and (2) using data from an at-sea observer programme and sentinel fishery programme in 2001 and 2002. The questionnaire survey had a low response rate (22%) and provided bycatch estimates of 2,215 (95% CI 1,151-3,662) and 2,394 (95% CI 1,440-3,348) porpoises in 2000 and 2001, respectively. The low number of hauls monitored by at-sea observers prevented the estimation of bycatch levels for several zones and the study area as a whole, and provided only imprecise estimates for all other zones. The results from questionnaires indicated a 24-63% reduction in harbour porpoise bycatches since the late 1980s, whereas the at-sea observer programme provided bycatch levels for 2001 and 2002 that were unreliable and underestimated, approaching one quarter of those documented in the late 1980s. Although both indices indicated a decrease in bycatches since the late 1980s, the magnitude of this change remains uncertain given the weaknesses associated with the two approaches. Considering the maximum population rate of increase (Rmax) for harbour porpoises as 4% and the lower and upper 95% confidence limits (1,440-3,348) of our most reliable estimate of bycatches (i.e. the 2001 questionnaire survey results), the harbour porpoise population in the Gulf of St. Lawrence would need to be at least 36,000-83,700 individuals for current incidental catches to be sustainable. If the rate of increase is less than maximal, e.g. 0.5Rmax or 2%, then 72,000-167,400 harbour porpoises would be needed to attain sustainability. Kingsley and Reeves (1998) estimated that an average 36,000 to 125,000 porpoises occupied the Gulf of St. Lawrence during the summers of 1995 and 1996. Although the trajectory of the population since it was last surveyed in 1996 is uncertain, these findings suggest that bycatch levels might remain a cause for concern for the harbour porpoise population in the Gulf of St. Lawrence. The results from the comparison between the sentinel fishery and the commercial fishery subjected and not subjected to at-sea observations suggest that fine-scale temporal and spatial changes in fishing activities may greatly affect harbour porpoise bycatch levels.

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Winther, Morten. "Bycatches of harbour porpoises (Phocoena phocoena L.) in Danish set-net fisheries". J. Cetacean Res. Manage. 1, n. 2 (25 gennaio 1999): 123–35. http://dx.doi.org/10.47536/jcrm.v1i1.457.

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Data on bycatch of harbour porpoise (Phocoena phocoena L.) in the commercial Danish set-net fisheries were sampled from 5,591km nets in the period 1992 to 1998 using independent observers. A total bycatch of 325 harbour porpoises was reported. Cluster analysis was used to stratify the sampled fishing trips and official catch statistics into a number of different m6tiers defined by the target species for the trips. Extrapolation of the observed bycatch rate to total fish landings of the Danish set-net fleet gave an average annual bycatch of 6,785 (CV 0.12) for the North Sea fisheries in the period 1994-1998. Sampling was not sufficient to estimate total bycatch for other areas. Bycatch was observed in Kattegat but not in the Baltic Sea. Generalised Linear Models were used to identify significant factors for bycatch in the North Sea. The bycatch rate, given as number per length of nets x soak time, was significantly lower in fisheries for flatfish compared to roundfish fisheries. The highest bycatch rate was in the cod fishery over wrecks and no bycatch was observed in the sole fishery. Significant seasonal variation of bycatch was identified with the highest bycatch rate in the first and third quarter of the year. Bycatch rates had not changed in the observed period and there was no significant difference in bycatch rates between sub-areas.

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Gray, Charles A., e Steven J. Kennelly. "Bycatches of endangered, threatened and protected species in marine fisheries". Reviews in Fish Biology and Fisheries 28, n. 3 (29 maggio 2018): 521–41. http://dx.doi.org/10.1007/s11160-018-9520-7.

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Cullet, Philippe, e Annie Patricia Kameri‐Mbote. "Dolphin bycatches in Tuna Fisheries: A smokescreen hiding the real issues?" Ocean Development & International Law 27, n. 4 (gennaio 1996): 333–48. http://dx.doi.org/10.1080/00908329609546088.

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Faruque, Hasan, e Hiroyuki Matsuda. "Conservative Scoring Approach in Productivity Susceptibility Analysis Leads to an Overestimation of Vulnerability: A Study from the Hilsa Gillnet Bycatch Stocks of Bangladesh". Fishes 6, n. 3 (24 agosto 2021): 33. http://dx.doi.org/10.3390/fishes6030033.

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Despite different approaches used to assign the risk scores for missing information in productivity susceptibility analysis (PSA)—a widely used semi-quantitative risk assessment tool for target and non-target fisheries stocks—for the selected attributes of a given species, no formal comparison has been made between scoring approaches in terms of how well they can predict species vulnerability. The present study evaluated the PSA findings of 21 bycatch stocks of the Hilsa (Tenualosa ilisha) gillnet fishery of Bangladesh using two different scoring approaches (the conservative scoring approach, CSA; and the alternative scoring approach, ASA) to determine the most reliable approach to minimize false estimates of species vulnerability. Our analysis revealed that the V scores increased by 0.0−0.20 with a mean value of 0.09 for 21 selected bycatches when CSA was applied. The inconsistency between the vulnerability (V)-score-suggested fishing status (V ≤ 1.8 = underfishing, V > 1.8 = overfishing) and the fishing status defined by exploitation rate (E > 0.5 = overfishing, E < 0.5 = underfishing) were 38.1% and 19.0% under CSA and ASA, respectively. Likewise, the consistency between the V-score-suggested fishing status and fishers’ perceived catch trends was found to be higher when using ASA than when using CSA. Our analysis suggests that CSA could overestimate species vulnerability. Therefore, ASA is more reliable than CSA in PSA, which may increase the confidence of fisheries stakeholders in PSA.

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Szostek, Claire L., Lee G. Murray, Ewen Bell, Gwladys Lambert e Michel J. Kaiser. "Regional variation in bycatches associated with king scallop (Pecten maximus L.) dredge fisheries". Marine Environmental Research 123 (febbraio 2017): 1–13. http://dx.doi.org/10.1016/j.marenvres.2016.11.006.

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Östman, Örjan, Göran Sundblad, Peter Ljungberg, Sandra Levin, Martina Blass, Marju Kaljuste, Iris Dahlin, Rebecka Svensson e Jens Olsson. "Catches, bycatches and stock indicators of fisheries targeting cyprinids along the Swedish Baltic Sea coast". Fisheries Research 268 (dicembre 2023): 106829. http://dx.doi.org/10.1016/j.fishres.2023.106829.

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Herinirina, Patricia A., Lionel Bigot, Patrick Frouin, Huguette T. E. Volandrae, Roddy M. Randriatsara, Faustinato Behivoke, Lantoasinoro Ranivoarivelo e Marc Léopold. "Seagrass macroinvertebrate bycatches support mosquito net trawl fishery in Madagascar". Aquatic Living Resources 36 (2023): 18. http://dx.doi.org/10.1051/alr/2023014.

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The use of mosquito nets, primarily for targeting small and/or juvenile fish, has rapidly increased in Western Indian Ocean shallow seagrass beds and coral reefs over the last 20 years. However, to date, invertebrate by-catch by locally-made fishing gear has not been reported. We studied the mosquito net trawl fishery in seagrass areas in the Bay of Toliara, Southwest Madagascar through the GPS tracking of fishers from August 2018 to February 2019. Catches were monitored through monthly landing surveys to characterize spatial temporal patterns in the abundance and diversity of macroinvertebrates in the seagrass beds. Fishing was carried out at low tide, mostly at night, by fishers pulling a hand-made trawl net of varying dimensions. Overall, 43 macroinvertebrate taxa were identified out of 217,080 individuals collected from 109 catch samples. Catches were generally composed of crustaceans (mainly Portunidae, Processidae, Penaeidae, and Alpheidae). The crab Thalamita mitsiensis largely dominated the abundance and biomass of the macroinvertebrate assemblage (from 6% to 100% and from 5 to 100% of the overall density and biomass, respectively). Macroinvertebrates composed 1.5% to 100% of the total catch per trip (i.e., 4–55 kg trip−1). They were sold for human consumption or animal feed, which provided additional income to fishers (USD 1–24 trip−1 and 1–72% of catch income per trip). This study revealed that macroinvertebrate resources provide valuable by-catch to small-scale fishers in Southwest Madagascar. This bycatch generates income that further encourages the use of mosquito net trawls and exacerbates their negative effects on coastal seagrass ecosystems and fisheries.

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Cox, Tara M., Andrew J. Read, Andrew Solow e Nick Tregenza. "Will harbour porpoises (Phocoena phocoena) habituate to pingers?" J. Cetacean Res. Manage. 3, n. 1 (25 maggio 2023): 81–86. http://dx.doi.org/10.47536/jcrm.v3i1.904.

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Large bycatches of harbour porpoises (Phocoena phocoena) occur in gillnet fisheries throughout the Northern Hemisphere. Several mitigation measures, including acoustic deterrent devices or ‘pingers’, have been used in efforts to reduce this bycatch. The potential exists for harbour porpoises to habituate to pingers, thus reducing their effectiveness over time. A field experiment was conducted to test the hypothesis that porpoises habituate to the sound produced by pingers. Porpoise echolocation and movements were monitored around a mooring equipped with a pinger (Dukane NetMark™ 1000) for three months in summer 1998 in the Bay of Fundy. Using a mean-shift model it was estimated that porpoises were initially displaced 208m from the pinger (p = 0.019), but this displacement diminished by 50% within four days (p = 0.019). Using a probability model it was demonstrated that the probability of porpoises within 125m of the pinger initially decreased when the pinger was turned on, but then increased to equal the control in 10-11 days. Echolocation rate (p < 0.001) and occurrence (p < 0.001) were significantly reduced in the vicinity of the pinger. These results indicate that porpoises habituated to the Dukane NetMark™ 1000 pinger and are not alerted to echolocate in the presence of nets by pingers.

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Più fonti

Tesi sul tema "Bycatches (fisheries)"

McGowan, Conor P. "Incidental take and endangered species demography". Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5595.

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Thesis (Ph. D.)--University of Missouri-Columbia, 2008.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on June 9, 2009) Vita. Includes bibliographical references.

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Herrera, Guillermo E. "Spatial structure and informational asymmetry in the economics of multiple stock renewable resources /". Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/7425.

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Richter, Christoph. "Harbour porpoise and people : strategies for bycatch reduction in the Bay of Fundy /". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ36173.pdf.

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Secchi, Eduardo Resende, e n/a. "Modelling the population dynamics and viability analysis of franciscana (Pontoporia blainvillei) and Hector�s dolphins (Cephalorhynchus hectori) under the effects of bycatch in fisheries, parameter uncertainty and stochasticity". University of Otago. Department of Zoology, 2006. http://adt.otago.ac.nz./public/adt-NZDU20070118.162020.

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Incidental mortality in fisheries, especially gillnets, is one of the most important causes of decline of many species of cetaceans around the globe. Local populations of franciscana, Pontoporia blainvillei, and Hector�s dolphins, Cephalorhynchus hectori, have been subject to high levels of mortality in gillnets for several decades. This is due to a combination of extensive overlap in distribution of these coastal dolphins and large numbers of fishing nets. Stage-specific population dynamic models (without environmental stochasticity) suggest that both species have a low potential for population growth of approximately 0.2% (95% CI: -3.7% to 4.2%) to 3.4% (95% CI: 1.6% to 6.4%) for franciscana and 0.85% (95% CI: -1.0% to 2.6%) for Hector�s dolphins. Although the two species have similar population growth rates, they result from different life history strategies. Franciscana has a relatively low adult survival rate (0.86; SD = 0.016) which is compensated by a relatively high reproductive potential. The latter is a combination of early reproduction and high fecundity. Hector�s dolphin has a low reproductive potential, which is a combination of late reproduction and low fecundity, which is probably compensated by a relatively high adult survival rate (0.92; SD = 0.02) Apparent differences in growth rate among franciscana populations are possibly due to a combination of varying population-specific reproductive potential and, in some populations, inaccuracy in parameter estimates. Inaccuracy in estimating natural survival rates is also a cause for the low growth rate of Hector�s dolphins. The estimated low population growth rates of these species are insufficient to compensate for current levels of fishing-related mortality in some local populations, especially when environmental and/or demographic stochasticity is considered. Under these circumstances Banks Peninsula population would have a negative mean population growth rate of 0.54% (95% CI: -2.2% to 0.9%) and would decrease below its initial size in approximately 74% of the simulations. Stochasticity alone would decrease considerably the probability of the Banks Peninsula population to grow and recover from past and current high bycatch levels. Effects of stochasticity were also high for one of the franciscana stocks (i.e. stock from Franciscana Management Area II). In other areas (e.g. West Coast of the South Island; franciscana stock from FMA I) fishing effort and bycatch mortality rate seem not to be impeding population growth. Even in a stochastic environment and under current levels of fishing effort, the West Coast population and the franciscana stock from FMA I would grow at a positive rate of 0.32% (95% CI: -1.2% to 1.8%) and 3.1% (95% CI: 2.2 to 7.2%), respectively. Parameter uncertainty does not change the conclusion that immediate and extreme limitations on fishing practice and effort are necessary to increase the chances of recovery for some local populations/stocks. Fishing effort in New Zealand is regulated by a quota system. The quota system, the low number of fishing boats and the relatively low overlap between fishing nets and dolphins are probably the reasons for the positive population growth of Hector�s dolphins from the West Coast of the South Island. On the other hand, not even the Marine Mammal Sanctuary is sufficient to avoid negative mean population growth rate of Hector�s dolphins under current levels of fishing effort off Banks Peninsula. In Brazil, Uruguay and Argentina, where franciscana occurs, gillnet fisheries are not regulated. In some areas, faced with a declining fish stocks, fishermen have increased fishing effort to compensate for reduced catches, and the bycatch of franciscana has increased as a consequence. Strategies aiming at the conservation of these two species are likely to benefit other components of the ecosystem. Especially in the case of franciscana, reducing fishing effort is likely to promote the recovery of depleted fish stocks.

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Mackay, Alice I. "An investigation of factors related to the bycatch of small cetaceans in fishing gear". Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/1888.

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The bycatch of cetaceans in fishing gear is considered to be one of the biggest conservation threats to these species. Gear modifications have the potential to reduce these bycatches in global fisheries but there is little available information on how such modifications may change the fishing performance of gear, or indeed the behavior of cetaceans interacting with fishing gear. Generalized linear models (GLMs) were used to identify factors related to cetacean bycatches in UK bottom set gillnets. Rigged net height had a significant positive relationship with harbour porpoise (Phocoena phocoena) bycatch in ICES Area VII suggesting that lowering the profile of gillnets may have the potential to reduce bycatch rates. Modifications to gillnets, such as changing the amount of floatation or increasing the density of the meshes, were found to have significant effects on the active fishing heights of these nets. However, results from a bycatch mitigation trial in Argentina showed that the reduced fishing profile of one experimental net did not result in a concurrent reduction in the bycatch rate of Franciscana dolphins (Pontoporia blainvillei). While there was no significant difference in the rate, length or intensity of harbour porpoise encounters in the presence or absence of gillnets, the proportion of fast echolocation click trains were significantly higher when a net was present, indicating that porpoises either increased acoustic inspection of the net or foraging in the vicinity of the net. An analysis of underwater video footage collected inside trawl nets in an Australia fishery showed that bottlenose dolphins (Tursiops sp.) were present inside nets more frequently than they were caught and were actively foraging inside these nets. The orientation of dolphins inside these nets indicates that the current design of excluder devices used in this fishery could be improved to further reduce bycatch rates.

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Walmsley, Sarah Ann. "The assessment and management of bycatch and discards in the South African demersal trawl fishery". Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1005071.

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Over the past few decades it has become recognised that an ecosystem approach is required to manage world fisheries. Management strategies must ensure that non-target (bycatch) as well as target catches are sustainable. To achieve this, detailed commercial catch and biological information is required. The composition of catches made by trawlers operating off the south and west coasts of South Africa was investigated. Distinct fishing areas were identified on each coast, based on target species and fishing depth. Catch composition differed markedly among the areas defined. Although hake Merluccius sp. dominated South Coast catches, a large proportion of the catch was composed of bycatch. On the West Coast, hake dominated catches and this domination increased with increasing depth. On both coasts approximately 90% of the observed nominal catch was processed and landed. Estimates of annual discards suggested that the fishery discarded 38 thousand tons of fish per annum (16% of the nominal trawl catch). The data also indicated that hake discarding, the capture of linefish and the increased targeting of high value species might be cause for concern. Spatial analysis indicated that a variety of factors such as trawling position, catch size and catch composition affects bycatch dynamics. The monkfish Lophius vomerinus is a common bycatch species that has been increasingly targeted by demersal trawlers. This study showed that L. vomerinus is a slow-growing, long-lived species (West Coast males L∞ = 68.50cm TL, t₀ = -1.69yr, K = 0.10yr⁻¹; West Coast females L∞ = 110.23cm TL, t₀ = -1.54yr, K = 0.05yr⁻¹; South Coast sexes combined L∞ = 70.12cm TL, t₀ = - 0.80yr, K = 0.11yr⁻¹), that matures at approximately 6 years of age. These traits could have serious management implications for the species. Per-recruit analysis suggested that the stock might be overexploited, although further investigation is required to confirm this. Solutions were suggested for each of the concerns raised, taking cognisance of the differences observed between the South and West Coasts and the economic dependence of South Coast companies on bycatch. The needs of future research were considered.

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Winship, Arliss J. "Estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the North Sea". Thesis, St Andrews, 2009. http://hdl.handle.net/10023/715.

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Lobo, Aaron Savio. "The dynamics and impacts of trawl fishing along the Coromandel Coast of India". Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609292.

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Gedamke, Todd. "Developing a stock assessment for the barndoor skate (Dipturus laevis) in the Northeast United States". W&M ScholarWorks, 2006. http://web.vims.edu/library/Theses/Gedamke06.pdf.

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Booth, Anthony John. "Biology, stock assessment and management of the panga Pterogymnus laniarius on the Agulhas Bank, South Africa". Thesis, Rhodes University, 1998. http://hdl.handle.net/10962/d1005085.

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The panga, Pterogymnus laniarius (Cuvier, 1830), is a South African endemic sparid fish species. On the Agulhas Bank, South Africa it is a commercially important species, caught as bycatch in the hake directed trawlfisheries and targeted by offshore hook-and-linefishers. Recently there has been considerable interest shown in directing further fishing effort on this species. The lack of a suitable management procedure for teleost bycatch in South Africa was the principal reason for undertaking this study. This thesis investigates aspects the panga's life history, particularly those aspects that have management implications. A full knowledge of this species' distribution and abundance was necessary as this could highlight the existence of any nursery areas, ontogenetic migratory patterns and areas of high spawner biomass. The derived parameter estimates were then included as inputs into stock assessment models to determine the status and productivity of the resource. Growth studies based on sectioned sagittal otoliths revealed that the panga was a relatively slow growing fish with ages of 16 years being recorded. Growth was best described by the von Bertalanffy growth model as Lt=379.4(1-e⁻°·¹³⁽t ⁺ ¹·⁷⁸⁾). Total, natural and fishing mortalities were estimated at 0.36 year⁻¹, 0.28 year⁻¹ and 0.08 year ⁻¹, respectively. Detailed histological examination of the gonads revealed that panga is a late gonochorist, males and females maturing after a non-functional intersexual stage. Females mature at approximately 200 mm fork length or 4 years of age. Reproduction occurs throughout the year although there is a slight peak in winter. Gametogenesis was found to be similar to that of other sparid fishes and marine teleosts in general. The panga feeds predominantly on crustaceans with a distinct ontogenetic shift in feeding habits. Juvenile fish feed predominantly in the water column on mysids after which they move to the benthos. Subadult fish feed principally on ophiuroids and amphipods. Adult fish remain on or near the benthos, feeding predominantly on crabs, and on polychaetes, ophiuroids and fishes to a lesser extent. Several aspects of the panga's biology contribute to its ability to sustain a higher fishing pressure than other sympatric sparid species. These include its late gonochoristic reproductive style, protracted spawning season, maturation before recruitment and preference for soft substratum prey that enables it to utilise large areas of the Agulhas Bank. The panga's longevity, slow growth and low natural mortality rate, however, mitigated against these factors and were considered in the stock assessments. A heterogeneous Geographical Information System (GIS) was developed to analyse the distribution and abundance patterns of the panga. The GIS developed in this thesis makes a significant contribution towards the development of a South African Fisheries Information System to analyse and manage fish resources in general and bycatch resources in particular. The GIS developed in this study combines statistical Generalized Additive Modelling and standard GIS methods. Analysis of fourteen biannual fishery independent biomass surveys, disaggregated by life history stage, revealed that a nursery area for immature fish (<23 cm TL or < 4 years of age) exists on the Central Agulhas Bank. After sexual maturation, approximately 40% of the biomass migrated eastwards, colonising large areas of the Eastern Agulhas Bank.ilie location of the nursery area appears to be a result of the pelagic eggs and larvae being advected towards the coast in an anti-cyclonic gyre, stemming off the Agulhas current and later deposited over the Central Agulhas Bank. The weak bottom currents on the Central Agulhas Bank prevented juvenile loss to the Benguela system. The eurytopy of adult fish to various physical variables such as temperature, dissolved oxygen and stronger currents enabled it to reduce conspecific competition and migrate eastwards with distribution primarily determined by depth. Relative biomass estimates revealed a gradual increase in biomass of 5.5% per annum between 1988 and 1995. Predictions from yield-per-recruit, biomass-per-recruit and spawner biomass-per-recruit analyses showed that there was scope for further exploitation. A FSB₅₀ fishing strategy was considered to be the most appropriate fishing strategy as it did not reduce the spawner biomass-per-recruit to less than 50% of unexploited levels. Effort control was considered the most effective management tool as the age-at-50%-selectivity occurred after age-at-sexual maturity and releasing undersized fish was undesirable due to heavy mortalities resulting from severe barotrauma. The panga resource was also assessed using an age-structured production model. The values for the free parameters of the model were estimated using biomass indices derived from fishery-independent trawl surveys. Although the data were fairly uninformative about the productivity of the resource, the results indicated robustly, that the population has recovered from low levels in the mid-1970's and could sustain higher levels of fishing intensity. Risk analysis calculations were used to assess the sustainability of different catch scenarios. The level of sustainable catch was found to be sensitive to the selectivity pattern of the gear utilised. Both stock assessment methods used in this study to investigate the status of the panga resource showed that the resource could theoretically sustain higher catches. It was found that although the stock could be harvested using available fishing methods, the sympatry of this species with other commercial species was of concern as the latter would form a significant bycatch in a panga directed fishery. The failure of current harvesting methods to address the bycatch problem highlights the management problem in South Africa and stresses the need for creativity by both scientists and fishers in designing new and improved methods for selectively harvesting bycatch fish resources. Considering that no suitable method is currently available to fish the panga stock in a directed fishery the fishery should be managed as status quo until some suitable and efficient gear is developed.

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Più fonti

Libri sul tema "Bycatches (fisheries)"

Karp, William A. U.S. national bycatch report. Silver Spring, Maryland]: U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, 2011.

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K, Banerjee B. The shrimp fry by-catch in West Bengal. Madras: Bay of Bengal Programme, 1993.

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Stagliano, David M. Assessment of aquatic macroinvertebrates in USFS / BLM Lands of the Crooked and Sage Creek Watersheds. Helena (Mont.): Montana Natural Heritage Program, 2009.

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Weeks, Hal. 1997 Pacific Whiting Shoreside Observation Program. Newport, OR: Marine Finfish Program, Oregon Dept. of Fish and Wildlife, 1997.

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Dietrich, Kimberly S. Best practices for the collection of longline data to facilitate research and analysis to reduce bycatch of protected species: Report of a workshop held at the International Fisheries Observer Conference, Sydney, Australia, November 8, 2004. Silver Spring, MD: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Office of Protected Resources], 2007.

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1924-, Alverson Dayton L., a cura di. A global assessment of fisheries bycatch and discards. Rome: Food and Agriculture Organization of the United Nations, 1994.

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Southeast Fisheries Science Center (U.S.), a cura di. Analysis of sea turtle bycatch in the commercial shrimp fisheries of southeast U.S. waters and the Gulf of Mexico. Miami, FL: U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southeast Fisheries Science Center, 2002.

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McCracken, Marti L. Modeling a very rare event to estimate sea turtle bycatch: Lessons learned. Honolulu, Hawaii: U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Pacific Islands Fisheries Science Center, 2004.

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J, Pitcher T., Ratana Chuenpagdee e University of British Columbia. Fisheries Centre., a cura di. Bycatches in fisheries and their impact on the ecosystem. Vancouver, B.C: Fisheries Centre, University of British Columbia, 1994.

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Norris, James. Fishermen's guide to chinook salmon bycatch data from the NMFS observer program: Bering Sea/Aleutian Island pollock bottom, pollock midwater, and Pacific cod trawl fisheries. [Seattle, Wash.]: Alaska Fisheries Science Center, National Marine Fisheries Service, U.S. Dept. of Commerce, 1993.

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Più fonti

Capitoli di libri sul tema "Bycatches (fisheries)"

Mandelman, John W., Jeffrey R. Kneebone, Alexia Morgan, Jefferson Murua e Emily Jones. "Strategies to Reduce Fisheries Bycatch Mortality in Chondrichthyans". In Biology of Sharks and Their Relatives, 737–66. 3^a ed. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003262190-24.

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Koss, Mikołaj, Martin Stjernstedt, Iwona Pawliczka, Anja Reckendorf e Ursula Siebert. "Whaling, Seal Hunting and the Effect of Fisheries on Marine Mammals". In Marine Mammals, 33–47. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-06836-2_3.

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AbstractThere are various types of interactions between marine mammals and fisheries, and their presence in the same area inevitably leads to conflicts. Marine mammals may lose their lives as bycatch, which is the incidental catch of non-target species in fishing gear. On the other hand, some marine mammals specialise in feeding on fish caught in fishing gear, resulting in damaged and reduced catch as well as destroyed fishing gear. There are different methods to reduce bycatch and catch damage, such as reducing fishing efforts, using acoustic deterrent devices, employing temporal and zonal closure of fishing areas and using alternative fishing gear. Here we give an overview of whaling and sealing from historical and present perspectives, with examples for Baltic marine mammals. We present hands-on activities to familiarise students and teachers with investigations of prey remains, such as otoliths (fish ear stones) found in faeces, to learn about marine mammal diet. Additionally, we introduce a whaling role play designed as a debate between interest groups, to better understand whaling from different perspectives.

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Graham, Norman. "Technical Measures to Reduce Bycatch and Discards in Trawl Fisheries". In Behavior of Marine Fishes, 237–64. Oxford, UK: Wiley-Blackwell, 2010. http://dx.doi.org/10.1002/9780813810966.ch10.

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Supadminingsih, Fahresa N., Mochammad Riyanto e Ronny Irawan Wahju. "Condition of Horseshoe Crabs as Bycatch from Gillnet Fisheries in Mayangan Waters of Subang Regency, West Java, Indonesia". In International Horseshoe Crab Conservation and Research Efforts: 2007- 2020, 189–201. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-82315-3_13.

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Hall, M. "More on Bycatches: Changes, Evolution, and Revolution". In Fisheries Bycatch: Global Issues and Creative Solutions. Alaska Sea Grant, University of Alaska Fairbanks, 2015. http://dx.doi.org/10.4027/fbgics.2015.12.

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"Biology and Management of Dogfish Sharks". In Biology and Management of Dogfish Sharks, a cura di Tamee Mawani. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781934874073.ch28.

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Abstract.—The fishery for spiny dogfish Squalus acanthias within British Columbia (B.C.) has fluctuated greatly over the past 150 years. During the 1930s and 1940s it was one of the most valuable fisheries on the West Coast. Active management of this fishery began in 1977 after Canada extended its exclusive economic zone to 200 mi. The management of Pacific groundfish fisheries, including dogfish, is complex, and is further complicated by serious conservation concerns. Bycatch issues and the lack of full catch monitoring have been of particular concern. As a result, Fisheries and Oceans Canada (DFO) approached groundfish industry representatives to develop a plan to address these key issues. A program to make individual fishers more accountable for their harvest, to improve compliance with the DFO’s selective fishing and fishery monitoring policies, and to be consistent with Pacific fisheries reform was developed. This integration program was implemented in 2006 for commercial groundfish fisheries within B.C. As a result, at-sea monitoring was maximized to 100% and individual transferable quotas within each fishery allow fishermen to account for their groundfish bycatch on an annual basis. This new management system could help pave the way for other fisheries around the world to learn, adjust accordingly, and implement similar regimes.

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Bonanomi, Sara, Jure Brčić’, Alessandro Colombelli, Emilio Notti, Jacopo Pulcinella e Antonello Sala. "Fisheries Bycatch of Chondrichthyes". In Chondrichthyes - Multidisciplinary Approach. InTech, 2017. http://dx.doi.org/10.5772/intechopen.69334.

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"Catch and Release in Marine Recreational Fisheries". In Catch and Release in Marine Recreational Fisheries, a cura di Robert J. Trumble, Stephen M. Kaimmer e Gregg H. Williams. American Fisheries Society, 2002. http://dx.doi.org/10.47886/9781888569308.ch10.

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Abstract.—Management of the hook-and-line-only fishery for Pacific halibut Hippoglossus stenolepis in waters off the United States and Canada requires discard to the sea of Pacific halibut bycatch (out of season, undersized, or by fishermen without individual quotas or licenses). Depending on hook type and release methods, survival from longline discards can vary from nearly 100% to none. Conversion in the early 1980s from J-hooks, used by foreign fleets and the domestic halibut fleet, to circle hooks, now used by most domestic longline fishermen, increased survival potential through less damaging hooking locations. Bycatch mortality caused by a fishery was estimated by applying a discard mortality rate to the total halibut discarded. On-board observers collected viability data used to calculate annual fishery-specific Pacific halibut discard mortality rates and collected fisheryspecific bycatch rate data used to estimate total bycatch. Limits on bycatch mortality, which closed fisheries when exceeded, provided an incentive for the longline fleet to practice careful release. Estimated halibut bycatch mortality dropped following careful release regulations. Results of tagging studies on halibut released using careful release demonstrated that the distribution of hook injuries shifted to minor and moderate injuries compared with moderate and severe injuries when careful release did not occur. Tag return rates used to quantify survival by injury type led to criteria describing the injuries.

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Boyce, John R. "An Economic Analysis of the Fisheries Bycatch Problem*". In Fisheries Economics, 23–45. Routledge, 2020. http://dx.doi.org/10.4324/9780429288500-4.

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"Pacific Salmon: Ecology and Management of Western Alaska’s Populations". In Pacific Salmon: Ecology and Management of Western Alaska’s Populations, a cura di Diana L. Stram e James N. Ianelli. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781934874110.ch37.

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Abstract.—The Magnuson-Stevens Act emphasizes the importance of minimizing bycatch, to the extent practicable, as part of the goal to achieve sustainable fisheries. Measures to reduce Pacific salmon (Oncorhynchus spp.) bycatch for the eastern Bering Sea walleye pollock Theragra chalcogramma trawl fisheries have been developed and implemented, resulting in specific closed (no-fishing) areas when established bycatch limits for Pacific salmon are exceeded. These closure areas were designed based on analyses of groundfish observer data collected from 1990–1995, yet in recent years Pacific salmon bycatch in the pollock fishery has consistently exceeded the limits. As a result, large areas were closed to the fishery, and the spatial pattern of fishing by the pollock fleet was altered. An analysis of the effectiveness of the closed-area management system was reviewed by the North Pacific Fishery Management Council (Council) in 2005, and indicated that when areas were closed, salmon bycatch rates were often higher than observed earlier inside the closure areas. Thus, as an interim measure, the Council adopted a program in October 2005 to exempt vessels from the existing closed-area regulations so that near-real time inseason information could be used to establish dynamic closed areas where salmon bycatch levels are high. In this paper, we review information on the previous closed area management system and qualitatively characterize historical bycatch patterns using fishery observer data. Our results show that the spatial and temporal salmon bycatch patterns are highly variable between years. Variability in size and sex composition of the salmon bycatch adds to the complexity of developing effective management options aimed at minimizing the bycatch of the eastern Bering Sea pollock fishery. These results should assist managers in devising alternative approaches for managing salmon bycatch in the pollock trawl fisheries.

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Rapporti di organizzazioni sul tema "Bycatches (fisheries)"

Schram, Edward, Paul W. Goedhart e Pieke Molenaar. Effects of abiotic variables on the survival of discarded bycatches in North Sea pulse-trawl fisheries. IJmuiden: Wageningen Marine Research, 2019. http://dx.doi.org/10.18174/475614.

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van Overzee, H. M. J. Factsheet: Incidental bycatch monitoring in pelagic commercial fisheries (PETS). Stichting Wageningen Research, Centre for Fisheries Research (CVO), 2023. http://dx.doi.org/10.18174/634029.

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Börjesson, Patrik, Maria Eggertsen, Lachlan Fetterplace, Ann-Britt Florin, Ronny Fredriksson, Susanna Fredriksson, Patrik Kraufvelin et al. Long-term effects of no-take zones in Swedish waters. A cura di Ulf Bergström, Charlotte Berkström e Mattias Sköld. Department of Aquatic Resources, Swedish University of Agricultural Sciences, 2023. http://dx.doi.org/10.54612/a.10da2mgf51.

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Marine protected areas (MPAs) are increasingly established worldwide to protect and restore degraded ecosystems. However, the level of protection varies among MPAs and has been found to affect the outcome of the closure. In no-take zones (NTZs), no fishing or extraction of marine organisms is allowed. The EU Commission recently committed to protect 30% of European waters by 2030 through the updated Biodiversity Strategy. Importantly, one third of these 30% should be of strict protection. Exactly what is meant by strict protection is not entirely clear, but fishing would likely have to be fully or largely prohibited in these areas. This new target for strictly protected areas highlights the need to evaluate the ecological effects of NTZs, particularly in regions like northern Europe where such evaluations are scarce. The Swedish NTZs made up approximately two thirds of the total areal extent of NTZs in Europe a decade ago. Given that these areas have been closed for at least 10 years and can provide insights into long-term effects of NTZs on fish and ecosystems, they are of broad interest in light of the new 10% strict protection by 2030 commitment by EU member states. In total, eight NTZs in Swedish coastal and offshore waters were evaluated in the current report, with respect to primarily the responses of focal species for the conservation measure, but in some of the areas also ecosystem responses. Five of the NTZs were established in 2009-2011, as part of a government commission, while the other three had been established earlier. The results of the evaluations are presented in a synthesis and also in separate, more detailed chapters for each of the eight NTZs. Overall, the results suggest that NTZs can increase abundances and biomasses of fish and decapod crustaceans, given that the closed areas are strategically placed and of an appropriate size in relation to the life cycle of the focal species. A meta-regression of the effects on focal species of the NTZs showed that CPUE was on average 2.6 times higher after three years of protection, and 3.8 times higher than in the fished reference areas after six years of protection. The proportion of old and large individuals increased in most NTZs, and thereby also the reproductive potential of populations. The increase in abundance of large predatory fish also likely contributed to restoring ecosystem functions, such as top-down control. These effects appeared after a 5-year period and in many cases remained and continued to increase in the longer term (>10 years). In the two areas where cod was the focal species of the NTZs, positive responses were weak, likely as an effect of long-term past, and in the Kattegat still present, recruitment overfishing. In the Baltic Sea, predation by grey seal and cormorant was in some cases so high that it likely counteracted the positive effects of removing fisheries and led to stock declines in the NTZs. In most cases, the introduction of the NTZs has likely decreased the total fishing effort rather than displacing it to adjacent areas. In the Kattegat NTZ, however, the purpose was explicitly to displace an unselective coastal mixed bottom-trawl fishery targeting Norway lobster and flatfish to areas where the bycatches of mature cod were smaller. In two areas that were reopened to fishing after 5 years, the positive effects of the NTZs on fish stocks eroded quickly to pre-closure levels despite that the areas remained closed during the spawning period, highlighting that permanent closures may be necessary to maintain positive effects. We conclude from the Swedish case studies that NTZs may well function as a complement to other fisheries management measures, such as catch, effort and gear regulations. The experiences from the current evaluation show that NTZs can be an important tool for fisheries management especially for local coastal fish populations and areas with mixed fisheries, as well as in cases where there is a need to counteract adverse ecosystem effects of fishing. NTZs are also needed as reference for marine environmental management, and for understanding the effects of fishing on fish populations and other ecosystem components in relation to other pressures. MPAs where the protection of both fish and their habitats is combined may be an important instrument for ecosystembased management, where the recovery of large predatory fish may lead to a restoration of important ecosystem functions and contribute to improving decayed habitats. With the new Biodiversity Strategy, EUs level of ambition for marine conservation increases significantly, with the goal of 30% of coastal and marine waters protected by 2030, and, importantly, one third of these areas being strictly protected. From a conservation perspective, rare, sensitive and/or charismatic species or habitats are often in focus when designating MPAs, and displacement of fisheries is then considered an unwanted side effect. However, if the establishment of strictly protected areas also aims to rebuild fish stocks, these MPAs should be placed in heavily fished areas and designed to protect depleted populations by accounting for their home ranges to generate positive outcomes. Thus, extensive displacement of fisheries is required to reach benefits for depleted populations, and need to be accounted for e.g. by specific regulations outside the strictly protected areas. These new extensive EU goals for MPA establishment pose a challenge for management, but at the same time offer an opportunity to bridge the current gap between conservation and fisheries management.

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Stone, Robert P., Stephen D. Cairns, Dennis M. Opresko, Gary C. Williams e Michele M. Masuda. A guide to the corals of Alaska. US Department of Commerce, NOAA, NMFS Scientific Publications Office, gennaio 2024. http://dx.doi.org/10.7755/pp.23.

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The Magnuson-Stevens Fishery Conservation and Management Reauthorization Act of 2006 mandat¬ed the research and management of the nation’s deep-sea coral resources through establishment of the National Oceanic and Atmospheric Administra¬tion’s Deep Sea Coral Research and Technology Program. The challenge for Alaska was daunting, where expansive, world-class fisheries often coincided with extraordinarily rich coral habitats for a high-latitude region. The first chal¬lenge was to inventory known locations of deep-sea corals. Many coral records and some museum collections existed from Alaska, but the taxonomy of cor¬als was little studied and field iden¬tification of corals was problematic. Formal bycatch programs and research activities in recent decades provided many more specimens for taxonomic study, but guides to species were largely incomplete, inaccurate, and outdated given the fast pace of species discovery in Alaska. We provide a comprehen¬sive, up-to-date guide, detailing 161 coral taxa identified from museum collections, primary literature, and video records. Each profile includes a description, images for each taxon, taxonomic history, biology, ecology, geographical distribution, and habitat, including depth distribution. Corals are found in the six regions of Alaska but the coral fauna of the Aleutian Islands is by far the most species rich. The state of taxonomy for some coral groups is ex¬cellent, while others require additional collections and more taxonomic work. Construction of this guide resulted in descriptions of several antipatharian species, published separately from this guide (Alternatipathes mirabilis, Bathypathes alaskensis, B. ptiloides, B. tiburonae, and Parantipathes pluma) and the scleractinian Flabellum (Flabel¬lum) oclairi Cairns, sp. nov. described herein. The guide provides informa¬tion for targeting new collections and identifying areas of high abundance and indicator species of vulnerable marine ecosystems. Stakeholders can now more adequately assess Alaska’s coral resources and risks from natural and anthropogenic stressors.

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