652 



Fishery Bulletin 103(4) 



1 00 



75  



50 



25 



Month 



Jvjtt j\M S<# v O 1 * <W 



1500 



1000 = 



500 



Figure 2 



The mean abundance of flathead sole {Hippoglossoides elassodon) eggs in the 

 western Gulf of Alaska during the year. Standard deviation and number of 

 stations used for each time period are also shown. The abundance in March 

 was very low (0.01 eggs/10 m 2 >. 



high abundance. Early stage eggs were most abundant 

 in mid-water; they accounted for 79% of the total number 

 of eggs collected between 50 and 159 m depth. Sixty- 

 six percent of all eggs collected above 66 m depth were 

 middle- and late-stage A eggs. The largest numbers of 

 late-stage B eggs were found below 124 m depth, where 

 they accounted for 83% of all eggs collected. Mean egg 

 stage depth showed that as the eggs developed from the 

 early stages to the middle stages they rose toward the 

 surface (mean depth of the eggs changed from 54 to 28 

 m); then in the later stages of development the eggs sank 

 and hatched at depth. Late-stage B eggs were collected 

 significantly deeper (mean depth 90 ±37 m) than late- 

 stage A eggs (mean depth 35 ±7 m; ANOVA, P=0.007; 

 Tukey HSD multiple comparison test, P= 0.006). 



Larvae 



Geographic distribution and abundance Larvae were 

 found from early April to October, but they were most 

 abundant from mid-May to mid- June (Fig. 5). From 

 mid- to late April, larvae were most abundant near the 

 Kenai Peninsula (Fig. 6A), and as spring progressed 

 their abundance increased southwest along the Alaska 

 Peninsula (Fig. 6B). Peak abundance occurred during the 

 first two weeks of June in the southern portion of Shelikof 

 Strait (Fig. 6C). From mid- to late June larvae were most 

 abundant on the east side of Kodiak Island (Fig. 6D). 

 Although most of the surveys were conducted in this 

 area, it is possible that larvae may have been abundant 

 elsewhere in the study area during this time. From July 

 through October, only the area east of Kodiak Island was 

 surveyed, and larval abundance there was low. 



Larval drift Satellite-tracked drifters released in May 

 1994 and drogued at 40 m indicated that the Alaska 

 Coastal Current flow was strong and moving to the 

 southwest — typical surface current flow for this area 

 (Bailey 4 ). In May 1996, drifters showed that flow was 

 weak, disorganized and moving somewhat to the north- 

 east (Bailey et al., 1999). In early May 1994, very few 

 flathead sole larvae were collected; therefore the center 

 point of the flathead sole egg distribution was used to 

 infer the starting location of larval drift. Size-at-age 

 data have shown that the growth rate for flathead sole 

 larvae is 0.3 mm/day in Auke Bay, Alaska (Haldorson et 

 al., 1989). Using this growth rate, we determined that 

 larvae hatched in early May could have grown as much 

 as 6 mm in the 21 days between surveys. The size class 

 of larvae greater than 9 mm was assumed to include 

 larvae that had hatched from the eggs present in early 

 May. The location of the centers of distribution of the 

 early May eggs and late May larvae indicated that the 

 larvae had drifted southward over the continental shelf 

 (Fig. 7). In 1996 all the larvae collected in early May 

 were 7.1 mm and smaller (range 4.2 to 7.1 mm). The 

 area was surveyed 26 days later, and growth of about 

 8 mm could have occurred between surveys. For larvae 

 collected at the end of May, the size group longer than 12 

 mm was assumed to include the early May larval group. 

 The location of the centers of distribution of the early 

 May and late May larvae showed that the larvae were 

 retained at nearly the same location (Fig. 8). 



4 Bailey, K. M. 2002. Personal commun. NOAA, Alaska 

 Fisheries Science Center, 7600 Sand Point Way NE, Seattle, 

 WA 98115. 



