Porter: Temporal and spatial distribution and abundance of eggs and larvae of Hippoglossoides elassodon 



653 



B 



172° 168° 164' 160° 



148" 144" 172' 168° 164° 160 156" 152' 148° 144" 



168° 164° 160° 156 



164° 160° 156" 152° 148 "W 



C D 



172° 168" 164" 160' 156 152° 148° 144" 172° 168° 164° 160° 156° 152° 148" 144" 



164° 160° 156° 152° 148° 



168° 164° 160° 156° 152 148 W 



egg abundance per 10 m 2 

 ZD0 I !0-10 



; 10-50 □ 50-100 



5iiS 1 00-200 



I > 200 



Figure 3 



The geographic distribution of flathead sole (H. elassodon) eggs in the western Gulf of Alaska 

 during the spawning season; I A) March, (B) early to mid-April, (C) early to mid-May, ID) early 

 to mid-June. 



Vertical distribution There were similar trends in the 

 vertical distribution of larvae among tows (Fig. 9). 

 Abundance peaked at about 15 to 30 m below the sur- 

 face, then decreased, and larvae were collected from the 

 deepest sampling depth interval from one tow (1996A; 

 Fig. 9). Because the tows were alike, to increase sample 

 size in the depth intervals, we pooled data from simi- 

 lar depth intervals but from different tows for fur- 

 ther analyses. Larval abundance was highest near the 

 surface and at the deepest depths sampled (Fig. 9). 

 In Auke Bay, Alaska, flathead sole larvae migrated 

 vertically at night no more than 15 m, ending at 20 m 

 depth, and they were less aggregated (Haldorson et al., 

 1993). This depth was much shallower than the depth 

 at which larvae and late-stage eggs were collected in 

 tow 1996A (sampling depth interval was 174-236 m). 

 Therefore the deep concentration of larvae in 1996 was 

 probably due to eggs hatching rather than to vertical 



migration. The deepest sample comprised embryos and 

 larvae (the larvae, however, were too damaged to deter- 

 mine whether they were prefeeding or feeding larvae), 

 and samples collected above 100 m were a mixture 

 of embryos and prefeeding larvae (29%), and feeding 

 larvae (71%). The smallest larvae (<5 mm) were found 

 in deepest water (mean depth 166 ±32 m), and larger 

 larvae (>5 mm) were found in shallower water (above 

 about 60 m depth; ANOVA, P<0.001; Tukey HSD mul- 

 tiple comparison test, P<0.001). The size distribution of 

 the larvae indicated that soon after hatching they rise 

 to the surface to feed. 



Discussion 



Flathead sole inhabit the continental shelf of the North 

 Pacific Ocean, and the area used for the present study 



