192 



Fishery Bulletin 98(1) 



and time of day for all sharks combined (AN OVA, 

 P=0.77). Water temperature decreased linearly with 

 depth (r2=0.61» and ranged from 5.9° to 9.0°C. 



The most abundant shark (by weight) was the shovel- 

 nose dogfish (Deania calcea), which represented 32.59^ 

 of the shark catch in 1990, 50.59c in 1993, and 37.2'7f 

 overall. The longnose velvet dogfish (Centroscymnus 

 crepidater), southern lantern shark (Etmopterus gran- 

 ulosus), and Owston's dogfish (Centroscymnus owstoni ) 

 also formed large proportions of the shark catch (Table 

 1). The largest catch (by weight) for any species of 

 shark in a single trawl was 850 kg for D. calcea 

 (area 5), followed by 441 kg for C. owstoni (area 1). 

 Although sharks dominated the catch in some trawls, 

 they formed only 4.2% of total biomass collected in 

 trawls. Even the most abimdant species (D. calcea) 

 accounted for only 1.6% of total biomass caught (Table 

 1). The highest estimate for number of individuals of 

 any species of shark captured in a single trawl was 308 

 for D. calcea, followed by 194 for E. granulosus. 



The most abundant shark in terms of number of 

 individuals captured was E. granulosus, which was 

 present in 79.3% of trawls (Table 1). Deania calcea and 

 C crepidater were also captured in large numbers and 

 appeared in a high proportion of the trawls. For three 

 of the larger species of squalids (the leafscale gulper 

 shark, Centrophorus squamosus; the Plunket shark, 

 Scymnodon plunketi; and the kitefin shark, Dalatias 

 licha ) few individuals were captured, and these species 

 occurred in a low percentage of the trawls (Table 1). 

 Preliminary examination of stomach contents revealed 

 that orange roughy were most common in stomachs of 

 E. granulosus and C. owstoni, but were also consumed 

 by C. squamosus and D. licha. 



Abundance 



There was a significant difference between mean 

 densities (kg/km'^) caught in the two surveys for 

 E. granulosus, C. owstoni, C. crepidater and Apris- 

 turus spp., but not for the other species (ANOVA, 

 P<0.01). A comparison of common areas that were 

 fished in both surveys (areas 6, 8, 9, and 10) showed 

 that there was no significant difference between the 

 densities of any of the species for the two surveys 

 (^test, P>0.01), and data from common areas for the 

 two surveys were therefore combined. In the orange 

 roughy survey, there was a significant difference 

 among areas for densities of all species except D. 

 licha, whereas in the oreo survey, significant differ- 

 ences were observed among areas for only two spe- 

 cies, C. crepidater and D. calcea (ANOVA, P<0.05). 

 The highest densities for all sharks combined were 

 recorded at the eastern tip of Chatham Rise, in areas 

 5 and 6 (1003.4 and 2249.1 kg/km^), and the lowest 

 were in the southwestern areas 8 and 10 (257.7 and 

 254.4 kg/km2). 



Composition of the shark catch varied consider- 

 ably with location fished. In areas on the north of 

 Chatham Rise, closest to New Zealand (areas 1 and 

 2), the catch was dominated by C. owstoni and C. 

 crepidater, which accounted for 84% of the shark 

 catch by weight (Fig. 3). On the mid-north of Cha- 

 tham Rise (area 3), C. owstoni and C. crepidater still 

 formed the majority of the catch; however D. calcea 

 was also abundant and all eight major taxa were 

 recorded. The northeast of Chatham Rise included 

 those areas (4 and 5) where the most trawls were 

 conducted. Here, C. crepidater still formed a large 



