strained to shallower water in the day as compared 

 with the southern subpopulation. 



The clearest case of vertical migration was that 

 of Gadus macrocephalus (Ihbles 3, 4), which was 

 most abundant at 20-30 m in the day and deeper than 

 50 m at night. The migration of this species was 

 primarily responsible for the increased total abun- 

 dance of larvae near the bottom at night (Fig. 3). This 

 pattern of movement is similar to that observed for 

 larval Ammodytes personatics by Yamashita et al. 

 (1985), who suggested that this reverse vertical 

 migration allowed feeding in daytime and avoidance 

 of migrating predators at night. This nocturnal de- 

 scent, not previously reported for Gadus larvae, 

 should be confirmed with further sampling. Gadus 

 morhua larvae 3.8-4.9 mm long move from deeper 

 water in the day to 0-2 m at night, and descend in 

 the water column with growth (Hardy 1978). Lar- 

 vae of another gadid, Melanogrammus aeglefinu^, 

 are most common in the thermocline and their depth 

 of greatest abundance fluctuates as the thermocline 

 depth changes with rotary tidal currents, causing oc- 

 casional descent in the water column at night (Miller 

 et al. 1963). 



Offshore taxa in Oregon coastal waters should oc- 

 cur in greatest numbers during onshore surface 

 water transport during winter and early spring. This 

 was true in our study for the mesopelagic Myc- 

 tophidae and Bathylagidae, but not for other offshore 

 assemblage taxa (Tkbles 5, 6, 7). Almost all of the 

 bathylagid and myctophid larvae except Steno- 

 brachiv^ leucopsaru^ were found below 30 m. 

 Ahlstrom's (1959) work confirms these general 

 distributions; he found most larvae of the genera 

 taken in this study (Electrona = Protomyctophum; 

 Laynpanyctus = Stenobrachiu^) at depths >56 m, 

 beneath the thermocline, except Stenobrackius. He 

 found Stenobrachius to have the shallowest distribu- 

 tion of all myctophid larvae in his study (0-41 m). 

 Richardson and Pearcy (1977) also found Steno- 

 brachius larvae to be in shallow waters (0-50 m) with 

 many at 0-10 m during the day. The distribution of 

 larval mesopelagic fishes, or other offshore taxa, can- 

 not be related to the depth of onshore transport 

 because virtually nothing is known about the depth 

 of winter onshore transport off Oregon (Peterson et 

 al. 1979; Huyer*). Both deep and surface dwelling 

 larvae of mesopelagic fishes collected in our study 

 appear to be transported onshore, however, sug- 

 gesting that transport occurs over a broad depth 

 range off Oregon. 



*A. Huyer, Associate Professor, Oregon State University, Cor- 

 vallis, OR 97331, pars, commun. 29 September 1983. 



FISHERY BULLETIN: VOL. 83, NO. 4 



ACKNOWLEDGMENTS 



This research was supported by NOAA Office of 

 Sea Grant, Department of Commerce, under Grant 

 No. NA81-D-00086. We thank M. Yoklavich, J. 

 Shenker, and the crew of the RV Sacajawea for 

 assistance in sampling. We also thank W. G. Pearcy 

 and H. G. Moser for reviewing the manuscript. 



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