FISHERY BULLETIN: VOL. 71, NO. 



with water depth (Table 17). Average densities 

 ranged from to 20/m^ between 20 and 100 m 

 and from 735 to l,724/m2 between 150 and 567 m. 



Environmental features that contributed sub- 

 stantially to the observed correlations are the 

 low energy environment combined with the rel- 

 atively mild abrasive characteristics of the bot- 

 tom sediments. 



Densities of fish teeth, bones, and scales were 

 low (80/m- or less). Teeth were recovered at 

 only two stations (53 and 54), where water 

 depths were 179 and 366 m; densities were 20 

 to 30/m-. The teeth at station 53 were from the 

 blue shark, Prionace glauca, a cosmopolitan spe- 

 cies that commonly attains lengths of 2 to 3 m. 

 Fish scales were found at three stations, at water 

 depths of 49 to 106 m, and at densities of 10 

 to 20/m-. Fish bones were detected at 22 sta- 

 tions (Figure 20). Vertebrae and rib bones 

 were encountered most frequently but occasion- 

 ally skeletal sections from the oral and branchial 

 regions were taken. The small thin bones gen- 

 erally had a fresh appearance, whereas the lar- 

 ger thicker bones were often badly eroded and 

 stained brown. Fish bones were collected at 

 water depths from 38 to 366 m; densities ranged 

 from 10 to 80/m-. 



RELATIONS OF DENSITY TO SEDIMENTS 



A broad comparison of the geographic distri- 

 bution and density of fish remains (Figures 19 

 and 20) with bottom sediment types (Figure 2) 

 disclosed a moderately close correlation. The 

 most obvious aspects were the absence of fish 

 remains in gravel-sand mixtures, and an exceed- 

 ingly low density in coarse and medium sand 

 sediments. Conversely, fish remains were com- 

 paratively common in silt, sandy silt, and fine- 

 grained sand. Otoliths had highest densities in 

 the fine sand, whereas bones were common in 

 sediments composed chiefly of silt and clay with 

 admixtures of fine sand. 



DISTRIBUTION AND DENSITY 

 BY SPECIES 



Of the 26 fish species whose remains were re- 

 covered from the bottom sediments, only six 



were abundant or moderately abundant; Cera- 

 toscopelus maderensis, Citharichthys larctifrons, 

 Diaphus sp.-4, Lepophidium cervinum, Merluc- 

 cius bilinearis, and Myctophum sp. (Fish spe- 

 cies represented by otoliths are listed by station 

 in Table 15.) Each of these species occurred at 

 eight or more stations, and maximum densities 

 ranged from 60 to 2,160/m-. Four of the six 

 abundant species are pelagic forms (exceptions 

 are L. cervinum and M. bilinearis, although M. 

 bilinearis frequently is mesopelagic) . The most 

 common species was Ceratoscopelus maderensis. 

 Otoliths of this species occurred at 19 stations 

 and average density was 530/m-. 



Nearly all fish remains were collected in the 

 southern half of the area. The geographic dis- 

 tribution of otoliths of diff"erent species is illus- 

 trated in Figure 21. With few exceptions, oto- 

 liths of individual species were geographically 

 distributed in an east-west band across the area, 

 roughly parallel to the depth contours. A major 

 exception to this distribution was that for M. 

 bilinearis, the most widely distributed species. 

 It was found at 15 stations, most of which were 

 located on the outer continental shelf, but a few 

 otoliths occurred on the central and inner por- 

 tions of the shelf. This species is one of the few 

 whose remains were found in the inner-shelf 

 region. 



Water depths at which remains of individual 

 fish species occurred ranged from 44 to 567 m. 

 Considerable differences in depth range were 

 evident among species, probably in part because 

 of the sparse representation of some. Depth-of- 

 occurrence data, by species, are summarized in 

 Table 18 and Figure 22. Only two species, 

 "Stromateus" and Merluccius bilinearis, were 

 found at depths shallower than 50 m, and only 

 six occurred at less than 100 m. On the other 

 hand, 15 species were recovered from depths 

 greater than 200 m, and 6 from depths greater 

 than 360 m. The species that were distributed 

 over the widest depth range are Ceratoscopelus 

 maderensis and Citharichthys "larctifrons; their 

 remains were taken at depths from 95 to 567 m. 

 Other species whose remains were spread over 

 a wide depth range are: Benthosema glaciale, 

 Diaphus sp.-2, Diaphus sp.-4, and Lepophidium 

 cervinum. About 61 Vf of the species were found 



30 



