876 



Necropsy findings in sea turtles taken as bycatch 

 in the North Pacific longline fishery 



Thierry M. Work 



Hawaii Field Station 



National Wildlife Health Center 



U.S. Geological Survey 



300 Ala Moana Blvd., Room 5-231 



Honolulu, Hawaii 96850. 



E-mail address, thierryworkia'usgs.gov 



George H. Balazs 



Honolulu Laboratory 



Southwest Fisheries Science Center 



National Manne Fisheries Service, NOAA 



2570 Dole St. 



Honolulu, Hawaii 96822. 



Concern about interactions between 

 fisheries and marine turtles has in- 

 creased in recent years, particularly 

 since East Pacific leatherback turtles 

 (Derrnochelys coriacea) may become 

 extinct (Spotila et al., 2000). However, 

 relatively little published information 

 exists on interactions between sea 

 turtles and North Pacific longline fish- 

 eries. The most available literature on 

 the topic focuses on modeling data from 

 fisheries observers for estimating the 

 probability of animals dying and fish- 

 ery-induced mortality (McCracken'; 

 Kleiber-). A more recent study was 

 undertaken with satellite telemetry 

 and remote sensing to evaluate the 

 probability of interaction between 

 longline fisheries and loggerhead 

 sea turtles iCaretta caretta) and the 

 effects of hooking (Polovina et al., 

 2000; Parker, in press). 



Necropsies on turtles caught by 

 longline fisheries may provide ad- 

 ditional objective data on the causes 

 of mortality and the health of pelagic 

 turtles. Although ample literature ex- 

 ists on evaluating the health of benthic 

 coastal-residing immature sea turtles 

 in Hawaiian waters (Aguirre et al., 

 1994; Work and Balazs, 1999), noth- 

 ing is known about the health status 

 of pelagic sea turtles because of the 

 difficulty in locating animals (Boltcn 

 and Balazs, 1983) and the unavailabil- 

 ity of specimens for diagnosis. Most 



turtles caught in longline fisheries are 

 released alive (McCracken'; Kleiber^). 

 The few dead turtles that area recov- 

 ered can be returned to shore legally 

 only by observers (who are present in 

 only ~59c of the Hawaii-based North 

 Pacific fishing fleet) (Balazs et al, 

 1995). Nevertheless, examining freshly 

 dead turtles caught in longline fisher- 

 ies provides a unique opportunity to 

 gain insight into the health status and 

 diet of pelagic sea turtles. Our objec- 

 tive was to systematically evaluate all 

 available carcasses of fresh-frozen sea 

 turtles that had been caught in the 

 Hawaii-based longline fishery for an 

 evaluation of their health and to docu- 

 ment their diet. 



Methods 



Free-ranging marine turtles acciden- 

 tally taken as bycatch by the North 

 Pacific longline fishery were landed 

 on the fishing vessel and evaluated 

 for signs of life by fishery observers 

 employed by the National Marine 

 Fisheries Service. Sea turtles that 

 were judged to be dead by specific cri- 

 teria (Balazs et al., 1995) were stored 

 frozen and returned to Honolulu, 

 Hawaii, where we recorded weight (kg) 

 and body morphometries (cm). 



Gross necropsies entailed a complete 

 external and internal exam of all organ 



systems. We also recorded any identifi- 

 able stomach contents. Body condition 

 of turtles was subjectively classified as 

 good, fair or poor if coelomic and mesen- 

 teric fat reserves appeared ample, mod- 

 erate, or sparse, respectively. Postmor- 

 tem condition was classified as good, 

 fair, or poor depending on the gross ap- 

 pearance of organs during the nec- 

 ropsy. We classified turtles as lightly 

 hooked if the longline fish hook was 

 lodged in the mouth or externally, or 

 as deeply hooked if the hook was pres- 

 ent in the gastrointestinal tract caudal 

 to the glottis. Hooks were classified as 

 tuna (3.6 or 3.8 mm) or swordfish and 

 mustad (offset 8/0 or 9/0). 



Tissue samples (heart, lung, kidney, 

 liver, spleen, brain, stomach, small 

 intestines, skin, trachea, salt gland, 

 gonad, thyroid, pancreas, and brain) 

 were fixed in 10% buffered formalin, 

 sectioned at 5 pm and stained with 

 hematoxylin and eosin for microscopic 

 examination. Representative tissues 

 were stored frozen (-70°C) in sterile 

 plastic bags. Where gross necropsy 

 findings suggested infectious or in- 

 flammatory disease, swabs or tissues 

 were processed for microbiology. For 

 bacteriology, swabs were plated on Mc- 

 Conkey and blood agar and incubated 

 at 27°C and 37°C for 48 h. For virus 

 isolation, frozen tissues were homog- 

 enized, the supernate filtered through 

 a 0.22-pm filter, and plated on green 

 sea turtle embryo fibroblasts (Moore 

 etal.. 1997). 



' McCracken, M. L. 2000. Estimation of 

 sea turtle take and mortality in thie Ha- 

 waiian longline fisheries. Administra- 

 tive Report H-00-06, 29 p. Southwest 

 Fisheries Science Center, Nat. Mar. Fish. 

 Service, NOAA. 2570 Dole St.. Honolulu, 

 HI 96822. 



- Kleiber, P. 1998. Estimating annual takes 

 and kills of sea turtles by the Hawaiian 

 longline fishery. 1991-97, from observer 

 program and logbook data. Administra- 

 tive Report H-98-08, 21 p. Southwest 

 Fisheries Science Center, Nat. Mar. Fish. 

 Serv.. NOAA, 2570 Dole St., Honolulu, HI 

 96822. 



Manu.script accepted 28 May 2002. 

 Fish. Bull. 100:876-880 (2002). 



