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Fishery Bulletin 92(2). 1994 



(Fig. 6), there were few small larvae caught at night, 

 which cannot be explained by gear avoidance. Since 

 the majority (>95%) of these lengths were from lar- 



100 200 300 400 500 600 

 NO./1000 m J 



Figure 3 



Vertical distribution of all larvae ex- 

 cluding walleye pollock (Theragra 

 chalcogramma) combined over all time 

 periods. Bars are mean abundances 

 per 1000 m 3 at each depth interval and 

 error bars are ± one standard deviation 

 about the mean abundance. 



vae collected from the same location (Series 9), sam- 

 pling variability cannot be invoked as an explana- 

 tion for this pattern. 



Discussion 



Our results indicate that the vast majority (>99%) 

 of pelagic eggs and larvae (excluding walleye pol- 

 lock) are distributed in the upper 100 m of the wa- 

 ter column during the spring months. Therefore, 

 sampling to this depth should be sufficient to char- 

 acterize the horizontal distribution patterns of these 

 species. Of the common taxa we examined, all but 

 H. elassodon have demersal eggs (Matarese et al., 

 1989). The transit time to surface waters following 

 hatching from demersal eggs is apparently of such 

 short duration that even newly hatched larvae were 

 rarely collected below 100 m. However, this does not 

 appear to be the case for walleye pollock, which 

 spawn at depths greater than 200 m in Shelikof 

 Strait, with mean depths of eggs and yolk-sac lar- 

 vae generally greater than 100 m (Kendall and Kim, 

 1989; Kendall et al. 1 ). 



The diel vertical distribution pattern that we ob- 

 served for several taxa is not the pattern typically 

 observed for most ichthyoplankton and for zooplank- 

 ton in general. The more common pattern, termed 

 a 'Type F migration (Neilson and Perry, 1990), in- 

 volves a nocturnal ascent into surface waters and 

 is undertaken by larvae of a diversity offish species. 



