189 



Abstract.— The distribution and abun- 

 dance of deep-sea sharks on Chatham 

 Rise, New Zealand, are described. 

 Sharks were collected as bycatch in two 

 deep-water trawl fisheries at a total 

 of 390 stations, which ranged in depth 

 from 740 to 1503 m. Sixteen species 

 of shark were caught: Deania calcea, 

 Centroscymnus crepidaten Etmopteriis 

 granulosus, and Centroscymnus owstoni 

 accounted for the largest portion of 

 the shark catch. Species that would 

 provide the highest yield of commer- 

 cially important liver lipids were not 

 abundant in trawls. All sharks com- 

 bined formed only 4.2^^^ of overall bio- 

 mass captured in trawls. Depth is a 

 major determinant of the composition 

 of the shark assemblage; both density 

 of sharks (kg/km-) and species diversity 

 were inversely proportional to depth. 

 Distributional patterns of the shark 

 community varied with location on Cha- 

 tham Rise, and species composition of 

 the shark catch varied with the spe- 

 cies of teleost targeted in deep-water 

 trawls. 



Assemblage of deep-sea sharks 

 on Chatham Rise, New Zealand 



Bradley M. Wetherbee 



Zoology Department 



2538 The Mall 



University of Hawaii 



Honolulu, Hawaii 96822 



Present address Northeast Fisheries Science Center 



National Marine Fisheries Service, NOAA 



28 Tarzwell Dr, Narragansett, Rhode Island 02882 



E-mail address: brad wetherbeea'noaa gov 



Manuscript accepted 12 July 1999. 

 Fish. Bull. 98:189-198 (20001. 



Sharks are common bycatch in deep 

 water fisheries around the world, 

 forming as much as 509?^ of the 

 catch in deep-sea trawls in areas 

 such as New Zealand and Austra- 

 lia (Deprez et al., 1990; Clark and 

 King' ). Most sharks captured in the 

 New Zealand and Australian deep- 

 water fisheries are dead by the time 

 they are brought to the surface and 

 are discarded, but some sharks are 

 retained for their liver oil. In Japan 

 and Australia, several species of 

 deep-sea shark in the family Squal- 

 idae are targeted in fisheries and 

 their liver oil is utilized. Although 

 the short-term potential of fisheries 

 directed towards deep-sea sharks 

 has been investigated for a few spe- 

 cies (Summers, 1987; Davenport 

 and Deprez, 1989), little informa- 

 tion on even basic biology is avail- 

 able for the species captured in 

 these fisheries. Thus, the effects 

 that deep-water fisheries have on 

 shark populations that are either 

 targeted directly or caught inciden- 

 tally are unknown. Information on 

 abundance, distribution, commu- 

 nity structure, reproduction, and 

 age and growth of deep-sea sharks 

 would improve understanding of 

 these effects. 



Shark liver oil contains commer- 

 cially important lipids, such as 

 squalene and diacyl glycerol ether, 

 which are used in cosmetic, phar- 

 maceutical, and other industries 

 (Deprez et al., 1990; Bakes and 



Nichols, 1995). The lipid composi- 

 tion of liver oil is quite variable 

 among and within species, and 

 consequently the most desirable 

 sharks are those individuals and 

 species that have the highest poten- 

 tial as a source for these valuable 

 lipids ( Davenport and Deprez, 1989; 

 Bakes and Nichols, 1995). There- 

 fore, understanding the distribution 

 and abundance of different species 

 of deep-sea shark, in conjunction 

 with knowledge of the lipid compo- 

 sition of their liver oil, is important 

 for optimal use of these resources. 



Some deep-sea sharks prey upon 

 commercially important teleosts 

 (Clark et al., 1989; Clark and King' ), 

 but the impacts of shark predation 

 on fish populations in terms of the 

 overall economic impact on the fish- 

 ery are unknown. Diet varies consid- 

 erably among even closely related 

 species of deep-sea shark (Com- 

 pagno et al., 1991; Ebert et al., 

 1992), and the level of predation 

 on commercially important species 

 of teleost by sharks also varies 

 among species (author's unpubl. 

 data). Information on the distri- 

 bution and abundance of deep-sea 

 sharks, in conjunction with knowl- 



1 Clark, M.R., and K.J. King. 1989. Deep 

 water fish resources off the North Island, 

 New Zealand: results of a trawl survey. 

 May 1985 to June 1986. New Zealand 

 Fisheries Technical Report 11, 56 p. MAF 

 Fisheries Research Center, RO. Box 297, 

 Wellington, New Zealand. 



