FISHERY BULLETIN: VOL. 85, NO. 1 



Table 2.— Species composition of copepods consumed by 

 sablefish larvae. Data are expressed as numerical percentages 

 of all copepods that were ingested by each size class in each 

 year. 



Table 3.— Size selection of copepods by sablefish larvae. Data are 

 expressed as a percentage of all copepods that were consumed 

 by each size class of larvae in each year. 



DISCUSSION 



A comparison of the diet of sablefish larvae in 

 1980 and 1983 revealed several differences. Most 

 notably, for larvae of all sizes, copepods <1 mm con- 

 tributed significantly more to the diet in 1983 than 

 in 1980. Appendicularians were the dominant prey 

 for large larvae in 1980, but were negligible in the 

 diet during 1983. Amphipods were only of conse- 

 quence in the diet of large larvae in 1983. Pteropods 

 comprised a substantial portion of the diet of small 

 and medium- sized larvae in 1980, but made a trivial 

 contribution to the diet in 1983 although ingested 

 by larvae of all sizes. 



Although concurrent zooplankton data are lack- 

 ing in this study, judging from the diet, prey popu- 

 lations were probably quite different in 1980 and 

 1983. As a result of the anomalous conditions dur- 

 ing 1983, a separate study extensively sampled zoo- 

 plankton off the Oregon coast (Miller et al. 1985), 

 where almost half (48%) of the sablefish larvae from 

 1983 were collected. 



In both 1980 and 1983, the timing of sablefish lar- 

 vae collections corresponded to the spring transi- 

 tional period off Oregon reported for previous years 

 (Peterson and Miller 1976, 1977). During this period 

 winds and currents shift, upwelling develops, and 

 the zooplankton is transitive between a winter 

 assemblage that is dominated by southern species 

 of copepods and a summer assemblage that is domi- 

 nated by copepods with northern affinities. During 

 1980, 8% of the copepods that were ingested were 

 northern species, representative of the spring transi- 

 tion, i.e., Pseudocalanus sp. and Acartia spp., 

 especially Acartia longiremis. In contrast, during 

 1983 as a result of the El Niiio event manifested 

 through increases in surface water temperatures, 

 sea level, and poleward currents, reductions in salin- 

 ities and coastal upwelling, and a depression of the 

 thermocline (Fiedler 1984; Huyer and Smith 1985; 

 McGowan 1985), only a partial spring transition 

 occurred, with southern (winter) species, especial- 

 ly P. parvus continuing to dominate the plankton 

 through July (Miller et al. 1985). The diet during 

 1983 reflected this same trend with P. parvus being 

 paramount in importance while northern species ac- 

 counted for <1.5% of the ingested copepods. 



The fact that the pteropod Limacina helicina, a 

 species with northern affinities which is the domi- 

 nant pteropod species off Oregon, was not very 

 abundant in 1983 (C. B. Miller^) correlates well with 



*C. B. Miller, College of Oceanography, Oregon State Univer- 

 sity, Corvallis, OR 97331, pers. commun. December 1985. 



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