FISHERY BULLETIN: VOL. 85, NO. 3 



|jLm, Bailey and Stehr^), this band was presumed 

 to be the hatching check and was counted as the 

 first increment. Nishimura and Yamada (1984) 

 found that increments were formed daily, begin- 

 ning with the day of hatching, on the otoliths of 

 laboratory-reared larval pollock. Similar obser- 

 vations have been made on larval walleye pollock 

 otoliths viewed with both light and scanning elec- 

 tron microscopy by Bailey and Stehr (fn. 8). Incre- 

 ments were, therefore, considered to be deposited 

 daily and increment counts were equated with 

 the age of the fish in days after hatching. 



The mean of two independent increment counts 

 was used in growth rate analysis. Age-at-length 

 data from each station were fitted separately with 

 simple linear regressions. Analysis of covariance 



8K. Bailey and C. Stehr, Northwest and Alaska Fisheries 

 Center, National Marine Fisheries Service, NOAA, 7600 Sand 

 Point Way, N.E., Seattle, WA 98115, pers. commun. 7 February 

 1985. 



was used to compare growth rates and Dunnett's 

 test of multiple comparisons identified signifi- 

 cantly different rates (Zar 1974). 



RESULTS 



Hydrographic Observations 



Temperature in the survey area varied from 

 just above 7°C at the surface at some stations to 

 slightly <5°C in deeper shelf water (Fig. 4). Tem- 

 perature gradually decreased with depth, and 

 temperatures in the upper 50 m (where most of 

 the walleye pollock larvae were found) were gen- 

 erally between 7.0° and 5.5°C. At the diel-vertical 

 distribution station, temperatures were similar 

 to those found throughout the area, although the 

 temperature gradient was more uniform than 

 elsewhere. In the upper 60 m at this station, tem- 



FlGURE 3.— Otolith from a 11.57 mm SL walleye pollock larva showing 27 daily growth increments. 

 The arrow near the focus indicates the first increment. Scale bar indicates 20 nm. 



504 



