Wetherbee: Assemblage of deep-sea sharks on Chatham Rise, New Zealand 



195 



700-1000 m versus 1300+ m 

 intei-vals. 



Morisita's index of dispersion 

 (/^) indicated that all species 

 of sharks tended to be aggre- 

 gated on Chatham Rise to some 

 degree. The three large squalid 

 sharks were the most aggre- 

 gated: S. plunketi (7^=104.5), 

 C. squamosus (82.4), D. licha 

 ( 55.4 ), followed hyE. granulosus 

 {24.3), Apristurus spp. (21.2), C. 

 owstoni (10.9), D. calcea (8.2), 

 and the most randomly distrib- 

 uted was C. crepidater {1^-5.4}. 



Discussion 



Kg sharli per km - 

 Number of Species 



12 



10 



3 



Sharks are abundant and 

 widely distributed on Chatham 

 Rise. Even though sharks form 

 a relatively small percentage of 

 the overall catch in deep-water 

 trawls they are frequently 

 caught by the hundreds and 

 occasionally dominate catches. 



The most abundant shark (by weight) on Chatham 

 Rise, D. calcea, was often caught in large numbers, 

 which suggests the presence of large aggregations. 

 However, this species was caught in a high percent- 

 age of trawls and was widely distributed on Chatham 

 Rise, which resulted in a fairly low index of disper- 

 sion (/^). D. calcea is abundant elsewhere in New Zea- 

 land waters, accounting for as much as 70% of the 

 shark catch off the North Island (Clark and King'). 

 Kobayashi (1986) reported that D. calcea was one of 

 the most common sharks in deep-water catches from 

 Japan as well. The most ubiquitous shark in terms 

 of presence at nearly all depths and locations on Cha- 

 tham Rise was E. granulosus, although this species 

 may have a fairly limited distribution outside of New 

 Zealand and southeast Australia. Tachikawa et al. 

 (1989) synonimized the New Zealand lantern shark, 

 E. baxterl, with the widely-distributed southern lan- 

 tern shark, E. granulosus; however, there may be sev- 

 eral species within the E. granulosus group and E. 

 baxteri may well be a valid species (Compagno et al., 

 1991; Wetherbee, 1996). 



Catsharks captured in trawls were keyed out to 

 five undescribed species ( A-E ) belonging to the genus 

 Apristurus (Paulin et al., 1989). That several hundred 

 specimens of these undescribed sharks were collected, 

 underscores the paucity of information on deep-sea 

 sharks. This genus also contains many undescribed 



Depth (m) 



Figure S 



Average density (kg/km- ±SDl of all sharks combined and number of species captured 

 within various depth intervals on Chatham Rise, New Zealand, for both surveys com- 

 bined. For comparison of mean densities among intervals with ANOVA, P = 0.011, 

 df=389. 



species in other locations, such as Australia (Last and 

 Stevens, 1994), and may eventually be recognized as 

 one of the most speciose genera of sharks. 



