Leatherback turtle captured by ingestion 

 of squid bait on swordfish longiine 



Robert A. Skillman 

 George H. Balazs 



Honolulu Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service, NOAA 



2570 Dole Street, Honolulu, Hawaii 96822-2396 



The leatherback turtle Dermochelys 

 coriacea is the only species of the 

 family Dermochyidae. The other six 

 extant marine turtles are hard- 

 shelled members of the family Che- 

 loniidae. The leatherback inhabits 

 the pelagic marine environment, ap- 

 parently only leaving to breed in 

 coastal waters. With recorded dives 

 to 475m, it is among the world's 

 deepest-diving vertebrates (Eckert 

 et al. 1986). With weights up to 916 

 kg, it is the world's largest turtle 

 (Eckert and Luginbuhl 1988). The 

 leatherback is listed as endangered 

 under the U.S. Endangered Species 

 Act, the International Union for 

 Conservation of Nature, and the 

 Convention on International Trade 

 in Endangered Species. Conse- 

 quently, fishery interactions involv- 

 ing the leatherback are of concern. 

 This paper reports an interaction 

 with longiine gear while fishing for 

 swordfish. 



Leatherbacks ingest and become 

 entangled in marine debris (Balazs 

 1985), and they are taken by oper- 

 ative fishing gear (Nishemura and 

 Nakahigashi 1990). Entanglement 

 has been reported with lobster pot 

 lines (Lazell 1976), drift nets (Balazs 

 1982, Wetherall et al. In Press); 

 pelagic longiine (Witzell 1984, 

 Tobias 1991); gillnets (Margaritoulis 

 1986); and swordfish Xiphias 

 gladius tangle nets (Frazier and 

 Brito Montero 1990). Interactions 

 with tuna and swordfish longiine 

 fishing have involved entanglement 

 and foul-hooking, particularly with 

 the leatherback's long flippers 



(Honolulu Star-Bulletin 1935, 

 Witzell 1984, Dollar 1991, Tobias 

 1991, USFWS 1969). In the Hawaii 

 swordfish fishery, sightings of 

 leatherbacks and reported interac- 

 tions are not rare, particularly in 

 the area of the seamounts above the 

 Northwestern Hawaiian Islands 

 (Robert Dollar, NMFS Honolulu 

 Lab., pers. commun.). It is not un- 

 common for leatherbacks to become 

 entangled in driftnets set north 

 of Hawaii between 30° and 45°N. 

 However, virtually nothing is 

 known about their overall distribu- 

 tion, abundance, and life history in- 

 cluding stock structure (Wetherall 

 et al., In press). The nearest col- 

 onies of nesting leatherbacks occur 

 in the eastern Pacific along the 

 coast of Mexico and Costa Rica and 

 in the western Pacific in peninsular 

 Malaysia. To our knowledge, inges- 

 tion of baited hooks has not been 

 reported in the literature. 



Leatherbacks are known to feed 

 on gelatinous, pelagic animals. 

 These include the medusa of sycho- 

 zoan coelenterates (true jellyfish) 

 (Bleakney 1965, Brongersma 1969) 

 and hydrozoan coelenterates (Por- 

 tuguese man-of-war Physalia are- 

 thusa) (Bacon 1970). Davenport 

 (1988) and Davenport and Balazs 

 (1991) have suggested the potential 

 importance of bioluminescence in 

 the predation of free-swimming 

 colonial tunicates (pyrosomas) by 

 leatherbacks during the night or on 

 deep dives. Neither fish (tuna bait) 

 nor squid (swordfish bait) have been 

 cited in the literature as prey of 



leatherbacks. Accordingly, Witzell 

 (1984) stated that leatherbacks are 

 not likely to be taken on a baited 

 hook. 



The present paper presents docu- 

 mentation of a leatherback captured 

 after ingesting squid bait on sword- 

 fish longiine gear. The chemical 

 light sticks used to attract sword- 

 fish may have attracted the leather- 

 back to the gear. 



On 24-25 January 1991, while ex- 

 perimental longiine fishing opera- 

 tions were being conducted for 

 swordfish from the NOAA research 

 ship Toumsend Cromwell, a leather- 

 back turtle was hooked and released 

 alive at lat. 26°58.3'N, long. 168° 

 53.5'W. The turtle swam vigorous- 

 ly while being hauled next to the 

 research vessel and after being 

 released. The hook line could be 

 seen coming from the turtle's 

 mouth, but the exact location of the 

 hook was not apparent. No blood or 

 external injuries were apparent. A 

 tree branch lopper on the end of an 

 extendable fiberglass pole was used 

 to cut the hook line a few centi- 

 meters from the turtle's mouth. The 

 estimated carapace length of the 

 turtle was 170 cm. The turtle was 

 too large to haul on board, and the 

 prevalence of sharks, including blue 

 shark Prionace glauca, made it im- 

 possible to enter the water for ac- 

 curate measurement or tagging. 

 Other site specifics included the 

 following: 2400 m bottom depth, 

 21.4°C sea surface-water tempera- 

 ture, 18.9°C air temperature, 

 150-180cm sea swells, northeaster- 

 ly trade winds at 15 kn, and approx- 

 imate depth of the upper mixed 

 layer at 85 m. 



Details of the set and gear are as 

 follows. The longiine gear consisted 

 of ~16km of 4.0 or 3.2mm mono- 

 filament main line suspended with 

 floats every 3 hook lines. The gear, 

 with 206 hooks, was set on 24 



Manuscript accepted 6 August 1992. 

 Fishery Bulletin, U.S. 90:807-808 (1992). 



807 



