FISHERY BULLETIN: VOL. 76, NO. 4 



in the water column extending to 385-460 m. We 

 estimate 0.61-1.24 myctophid fish/m^ based on av- 

 eraged day and night series (Table 10). No quan- 

 titative study comparable to ours has been made 

 in the open subarctic Pacific, but Pearcy and Laurs 

 (1966) provided data on the abundance of 

 mesopelagic fish near the Oregon coast. In two 

 cruises (August 1963), Pearcy and Laurs found 

 about 0.78 myctophid fish/m^ in the 0-500 m water 

 column at night; this estimate is based upon the 

 three numerically dominant myctophid fish cap- 

 tured (Pearcy and Laurs 1966, fig. 4), two of which 

 ranked 1 and 3 in abundance among myctophids 

 in our study. The average standing stock of all 

 mesopelagic fish found by Pearcy and Laurs ( 1966) 

 was 2.9 g wet weight/m^ in the 0-500 m water 

 column at night. Using a factor of 0.3 to convert 

 wet weight to dry weight, the average nighttime 

 standing stock is 0.87 g/m^, a value probably not 

 significantly different from our estimates based on 

 night samples (Table 9), especially since the 

 Pearcy and Laurs estimate is based on all 

 mesopelagic fish captured. Similar concentrations 

 of myctophids (about 0.6-0.8 fish/m^) are found in 

 the subtropical Pacific near Hawaii (Clarke 1973; 

 Maynard et al. 1975). However, many more 

 species of myctophids (47) occur there, and the 

 standing stock of myctophids (about 0.3-0.7 g wet 

 weigh t/m^) is somewhat less than our estimates 

 (0.23-0.53 g dry weight/m^, Table 9), probably be- 

 cause the fish are considerably smaller in average 

 size (Clarke 1973). 



With regard to sampling bias, we found no evi- 

 dence of light-aided avoidance of the nekton trawl 

 by either myctophids or other types of micronek- 

 ton occurring in the upper 385-460 m during the 

 daytime (Table 3). Consistent day-night differ- 

 ences in catches of organisms, such as those ob- 

 served for the largest size class ( >80 mm SL) of S. 

 leucopsarus and for Sergestes similis, were proba- 

 bly due to migration of these organisms below the 

 depth range of daytime sampling. The results of 

 the single very deep vertical series at Station P 

 (Table 4) support this interpretation. Further- 

 more, very deep vertical migrations of both species 

 are well documented in other parts of their geo- 

 graphical ranges in the North Pacific (Omori et al. 

 1972; Pearcy et al. 1977). 



In addition to determining vertical distributions 

 and vertical migrations of myctophid fishes, on 

 each cruise we also sampled zooplankton with a 

 smaller trawl (Frost and McCrone 1974). Analyses 

 of the zooplankton samples, together with data on 



stomach contents of the three most abundant myc- 

 tophids, are the subject of a report (in preparation) 

 on the feeding behavior of myctophids in relation 

 to their vertical distribution and the vertical dis- 

 tribution of their zooplankton prey. 



ACKNOWLEDGMENTS 



We extend special thanks to David Thoreson for 

 his assistance in all phases of the research. Bruce 

 Davies participated in the cruises and was primar- 

 ily responsible for nearly flawless operation of the 

 trawl. We were fortunate to obtain help and advice 

 on systematics of myctophid fishes from Richard 

 McGinnis. Karl Banse made many useful sugges- 

 tions on the manuscript. Others whom we wish to 

 thank for participating in the cruises or assisting 

 with the analysis include Gene Anderson, Arthur 

 Griffiths, Louise Hirsch, Jeffrey Napp, Bruce Nes- 

 set, Mary Nirini, Layne Nordgren, Scott Ralston, 

 Wesley Rowland, Gary Shigenaka, and Steve 

 Spyker. 



This research was supported by the Office of 

 Naval Research (Contract N00014-75-C-0502, 

 Project NR 083-012). Early development of the 

 trawl was supported by National Science Founda- 

 tion Grant GA-25385. 



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