MIDDLETON and MUSICK: ABUNDANCE AND DISTRIBUTION OF MACROURIDAE 



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 HEADLENGTH 



Figure 21— The gonadal maturity stages plotted against head 

 length for Coryphaenoides armatus. 



and temperature ranges; however, the N. aequalis 

 in this area were at the northern limit of their 

 geographic range, occurred in small numbers, and 

 may have been in direct competition with TV. bair- 

 dii. Although C. rupestris also occupied the lower 

 section of the two Nezumia spp. temperature and 

 depth regimes, direct competition was probably 

 low because of their dissimilarity in mouth size and 

 morphology and related differences in diet 

 (Podrazhanskaya 1971; Geistdoerfer 1975; McLellan 

 1977). 



Abundance and Density of 

 the Family Macrouridae 



In the study area the abundance of macrourids, 

 in water shallower than 2,000 m, was fairly constant 

 with respect to other bottom fishes. The average per- 

 cent of macrourids by number in each cruise was 

 16.6% in cruise 73-10 (June), 15.0% in 74-04 

 (December), 14.6% in 75-08 (September), and 18% 

 in 76-01 (January). The major peaks of abundance 

 were found between 300 and 400 m, where Coelorin- 

 chus c. carminatus was present, and around 800 m 

 where the complex comprised of Nezumia aequalis, 



N. bairdii, and Coryphaenoides rupestris dominated 

 (Fig. 22). In depths of over 2,000 m the numerical 

 dominance of C. armatus was evident. Some of the 

 minor inflections can be attributed to the contagious 

 distributions displayed by these fishes. 



The graph of macrourid biomass (Fig. 23), as per- 

 cent of the catch, was similar to that for numerical 

 abundance except for a shift in biomass from 800 

 m to below 1,000 m between January and June. This 

 was probably because of the seasonal movement of 

 the larger macrourid Coryphaenoides rupestris. Be- 

 tween about 1,400 and 2,200 m, macrourids made 

 up a very small portion of the biomass, although 

 their percent by number was comparable with lesser 

 depths. The dominant macrourid in this area, C. 

 carapinus, was small, and Antimora rostrata, a 

 large morid, was the most abundant member of the 

 benthic fish community from 1,300 to 2,500 m (Wen- 

 ner and Musick 1977). In depths >2,200 m the 

 biomass of C. armatus steeply increased with depth, 

 until it was the predominant member of the benthic 

 community. 



All the macrourid species, with the exception of 

 C. rupestris, maintained a fairly constant numerical 

 distribution from cruise to cruise There was ap- 

 parent variability for C. carapinus and C. armatus, 

 but this was due to the small number of samples 

 from deeper areas. Distribution of macrourids as the 

 percent of catch revealed a gradual replacement of 

 species with depth, and the predominance of C. ar- 

 matus in depths >2,500 m. 



Macrourids made up a major numerical portion of 

 the benthic fish community from 300 m to the 

 deepest station at 3,083 m. Macrourids were also 

 a main component of the biomass of the commu- 

 nities from 300 to 3,083 m, excluding the 1,300- 

 2,500 m range where the morid, A. rostrata, 

 dominated. 



Although Macrouridae is a dominant family in the 

 Norfolk Canyon area, the potential for a fishery is 

 essentially nonexistent. Coryphaenoides rupestris is 

 the only species which attains an appreciable size 

 in the mid-Atlantic area; a modal length of 46 cm 

 TL. However, this size is much smaller than typically 

 found in the North Atlantic and the density of 

 organisms is generally low (normally <0.86 in- 

 dividuals/100 2 ). In addition, C. rupestris demon- 

 strates a tropical submergence, being found deeper 

 in lower latitudes. The depth range of this species 

 in the Norfolk Canyon area (578-1,698 m), combined 

 with smaller size and lower density of organisms, in- 

 dicate that a commercial fishery would not be 

 economically feasible 



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