Shark Depredation and Unwanted Bycatch in Pelagic Longline

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Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries Table A9.4. (Continued) Author(s) Year Title Primary data Source(s) Notes Baum et al. 2003 Collapse and Conservation of shark populations in the Northwest Atlantic U.S. Logbook Reports on the decline of several coastal and pelagic sharks; abundance trends derived through CPUEs. Baum and Myers 2004 Shifting baselines and decline of pelagic sharks in the Gulf of Mexico (1954-57) Exploratory pelagic longline cruises; (1990s) POP Catch rates standardized and compared between two time periods (50s vs. 90s) in the GOM. Estimations of sharp declines in silky and oceanic whitetip populations. Beerkircher et al. 2004 SEFSC Pelagic Observer Program data summary fro 1992-2002 POP A comprehensive summation of POP data that includes shark catch data and depredated/live/dead catch data (without resolution of which species was source of depredation). Although not explicitly addressed here, has been a reliable data source for several subsequent reports addressing shark bycatch. Brooks et al. 2005 Standardized catch rates for blue shark and shortfin mako shark from the U.S pelagic logbook and U.S. pelagic observer program, and U.S weighout landings POP; U.S. Logbook; weighout-landings POP and logbook data both illustrate a decline in blue shark catches over time. This decline may indicate a change in catchability or a change in abundance. Campana et al. 2005 Catch, by-catch and indices of population status of the blue shark (Prionace glauca) in the Canadian Atlantic Scotia-Fundy Observer Program (SFOP) Foreign fishing efforts also accounted for; Blue shark catch almost all discarded; catches heavily underreported since many are cut-offs and bite-offs prior to reaching deck; mortality high through landings and discard mortality; although resilient, indications are that populations have declined in Canadian Atlantic in recent years. Harrington et al. 2005 Wasted Resources: bycatch and discards in U.S. fisheries POP (in relation to pelagic discards) Addresses incidental capture and discard across fisheries. Independently report on the pelagic LL fishery and sharks. Matsunaga and Nakano 2005 Estimation of shark catches by Japanese tuna longline vessels in the Atlantic ocean Japanese logbook data Emphasizes species differences. Most noteworthy is a decreasing trend in shark CPEU by Japanese vessels since the mid-1990s, before which time CPUE had been relatively stable since the early 1970s. Senba and Nakano 2005 Summary of species composition and nominal CPUE of pelagic sharks based on observer data from the Japanese longline fishery in the Atlantic Ocean from 1995 to 2003 Japanese observer data Species and catch rates summarized from specific six specific regions in the Atlantic; blue shark catch rates were highest across species, most notably in the Northwest Atlantic area that included the Grand Banks. Diaz and Serafy 2005 Longline-caught blue shark (Prionace glauca): factors affecting the numbers available for live release POP Expansion of previous investigations into the effects of LL soak time by introducing the effects of fish size, set duration, and water temperature on shark survival following longline capture Campana et al. 2006 Effects of recreational and commercial fishing on blue sharks (Prionace glauca) in Atlantic Canada, with inferences on the North Atlantic population SFOP; tournament catch records Similar to Campana et al. (2005) ICCAT document, integrating recreational component through tournament records. Diaz 2006 Estimation of large coastal sharks dead discards for the US pelagic longline fishing fleet NMFS 2006 Annual Report of the United States of America POP; U.S. Logbook U.S. Logbook* The amount of dead discarded shark carcasses estimated by species for the year 2004. * In relation to shark discards only (many additional data sources are utilized throughout report) in the section on shark fishery statistics. Presents temporal data on blue and mako shark landings and discard numbers. 140
USA Atlantic, Gulf of Mexico and Caribbean Pelagic Longline Swordfish and Tuna Fisheries Aside from the blue shark, recent declining trends in CPUE for other shark species caught in the U.S. Atlantic PLL fishery have been reported (e.g. Baum et al., 2003; Baum and Myers, 2004). A similar pattern since the mid-1990s has been echoed via observer reports from Japanese vessels operating in the Atlantic (e.g. Senba and Nakano, 2005). Although whether a true reflection of declines in abundance is a topic beyond the scope of this report, the decreases in catchability could be explained by underreporting, increased biteoffs from lighter gear (Brooks et al., 2005) and the historical use of J-hooks, changes in observed fishing effort through alternate shifts in gear or fishing distribution (Beerkircher et al., 2002), and most speculatively, the potentially successful establishment of personal fishing strategies and gear configurations by industry to reduce shark interactions. A9.2.2. Takes according to region and alternative factors Independent of seasonal and geographic factors, the highest rate of blue shark catch (spanning 1990-1997) coincided with swordfish as opposed to tuna targeted effort according to observer data (Hoey and Moore, 1999). Under the same conditions, swordfish were generally targeted in sets deployed between 2:00PM and 10:00PM with retrieval sometime between 4:00AM and 10:00AM. Alternatively, deployment and retrieval of tuna-targeted sets occurred at 2:00AM-12:00PM and 4:00PM-12:00AM respectively (Hoey and Moore, 1999). Although this could imply that blue sharks are more readily caught in the dusk to late evening hours and less frequently so in the early morning and daylight hours, the concordance between their catch rates and those of swordfish could also be a function of the high abundance of blue shark on the Grand Banks where swordfish have conventionally been the primary target species of the Northeast Distant (NED) fleet. The CPUE of blue sharks on the Grand Banks peaks in the summer months with reported rates of 0.10 (Cramer, 1997C). This differs with the CPUE estimates of 0.001 in more southeast zones (GOM, SAB, and FEC). As a function of the high catch rates for the species in the Northeast distant areas like the Grand Banks, Canadian fisheries account for a very high overall percentage of blue shark bycatch (DFO, 2002). Fig. A9.6. Standardized CPUE (number per 1000 hooks) and 95% confidence intervals for blue shark. All indices are standardized to the mean of the overlapping years (Brooks et al., 2005). Coupled with season and depth, behavioral thermoregulation also appears to be an important variable dictating the catch rates of blue sharks (John Hoey, personal communication). Although highly migratory and able to tolerate a wide array of temperature gradients, the species tends to prefer more temperate zones. Catch rates of blue sharks have been found to decline by 9.7-11.4% in response to an only 0.6 °C increase in sea surface temperature (Watson et al., 2005). Not surprisingly, it has also been shown that blue sharks tend to prefer subsurface depths that possess cooler temperatures (e.g. Simpfendorfer et al., 2002). However, more comprehensive studies on blue shark distribution according to full water column temperature profiles and thermocline dynamics are necessary before amending fishing practices in accordance with patterns in sea-surface temperatures. In a study which assessed catch characteristics in two southeastern zones, a more standardized CPUE estimate than could be assigned 141
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Shark Depredation and Unwanted Byca
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Contents Summary and Conclusions 1
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Contents Appendix 3. Fiji Pelagic L
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Contents Appendix 8. USA Hawaii Lon
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Chapter 1 Introduction and Methods
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Introduction and Methods 1.2. Metho
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Fishing Gear and Operational Charac
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Fishing Gear and Operational Charac
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Shark Catch Rates and Disposition T
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Chapter 4 National and Internationa
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National and International Measures
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Economic, Practical, Ecological and
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Economic, Practical, Ecological and
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Chapter 6 Industry Attitudes and Pr
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Industry Attitudes and Practices Lo
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Industry Attitudes and Practices Fi
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Chapter 7 Potential of Deterrents,
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Potential of Deterrents, Hotspot Av
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References Campana, S.E., L. Marks,
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References Neves dos Santos, M., Ga
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Appendix 5 Japan Pelagic Longline F
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Japan Pelagic Longline Fisheries Fi
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Shark Depredation and Unwanted Bycatch in Pelagic Longline

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