Quantifying the effects of fisheries on threatened species: the impact of pelagic longlines on loggerhead and leatherback sea turtles

The depletion of fish stocks from global fisheries has been a long-standing concern. More recently, incidental catch of non-target (termed bycatch) vertebrates also has been proposed as a serious conservation issue. Here we present a bycatch assessment for loggerhead and leatherback sea turtles that are incidentally caught by global pelagic longlines. We integrate catch data from over 40 nations and bycatch data from 13 international observer programmes. Despite infrequent rates of encounter, our analyses show that more than 200 000 loggerheads and 50 000 leatherbacks were likely taken as pelagic longline bycatch in 2000. Our analyses suggest that thousands of these turtles die each year from longline gear in the Pacific Ocean alone. Given 80‐95% declines for Pacific loggerhead and leatherback populations over the last 20 years, this bycatch level is not sustainable. Adopting a large-scale, synthetic approach is critical to accurately characterize the influence of global fisheries bycatch on globally distributed and imperilled pelagic vertebrates.

[1]  Ransom A. Myers,et al.  Collapse and Conservation of Shark Populations in the Northwest Atlantic , 2003, Science.

[2]  D. L. Alverson,et al.  By-Catch: Problems and Solutions , 2000 .

[3]  M. Hall.  On bycatches , 2004, Reviews in Fish Biology and Fisheries.

[4]  L. Crowder.  Leatherback's survival will depend on an international effort , 2000, Nature.

[5]  B. Worm,et al.  Rapid worldwide depletion of predatory fish communities , 2003, Nature.

[6]  Hal Caswell,et al.  Demography of the endangered North Atlantic right whale , 2001, Nature.

[7]  Larry B. Crowder,et al.  Fisheries Bycatch: Implications for Management , 1998 .

[8]  L. Crowder,et al.  The Impact of Turtle Excluder Devices and Fisheries Closures on Loggerhead and Kemp's Ridley Strandings in the Western Gulf of Mexico , 2003 .

[9]  L. Crowder,et al.  Life table analysis of long-lived marine species with implications for conservation and management , 1999 .

[10]  T. Polacheck,et al.  By-catch of Albatrosses and other Seabirds by Japanese Longline Fishing Vessels in the Australian Fishing Zone from April 1992 to March 1995 , 1997 .

[11]  H. Weimerskirch,et al.  Modelling the impact of fishery by-catches on albatross populations , 2001 .

[12]  D. Pauly,et al.  Fishing down marine food webs , 1998, Science.

[13]  L. Crowder,et al.  ESTIMATING FISHERY BYCATCH AND EFFECTS ON A VULNERABLE SEABIRD POPULATION , 2003 .

[14]  R. Gales,et al.  Seabird mortality in the Japanese tuna longline fishery around Australia, 1988–1995 , 1998 .

[15]  F. Paladino.  Pacific leatherback turtles face extinction Fisheries can help avert the alarming decline in population of these ancient reptiles , 2000 .

[16]  Larry B. Crowder,et al.  Predicting the impact of Turtle Excluder Devices on loggerhead sea turtle populations , 1994 .

[17]  Hal Caswell,et al.  HARBOR PORPOISE AND FISHERIES: AN UNCERTAINTY ANALYSIS OF INCIDENTAL MORTALITY , 1998 .