Porter: Temporal and spatial distribution and abundance of eggs and larvae of Hippoglossoides elassodon 649 



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150° 



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Umnak 

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Unimak 

 Island 





Shumagm 

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s Kodiak 

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Figure 1 



The western Gulf of Alaska where ichthyoplankton surveys were conducted in 1972 and from 

 1977 to 1999 by the Alaska Fisheries Science Center to examine the timing of spawning, 

 geographic distribution and abundance, and vertical distribution of flathead sole (Hippoglos- 

 soides elassodon). 



cesses that affect the drift of walleye pollock larvae 

 may also affect the drift of flathead sole larvae in this 

 area. For example, the drift of walleye pollock larvae in 

 Shelikof Strait can be slowed if they become entrained 

 in eddies that form there (Bailey et al., 1997). The 

 Alaska Coastal Current flows southwest through She- 

 likof Strait and branches just south of it; one branch 

 continues along the continental shelf, and the other 

 heads seaward (Bailey et al., 1997). Whether larvae will 

 stay near shore or move off shore is determined by one 

 or other of these two branches of the current. 



Information about the early life history of flathead 

 sole in the Gulf of Alaska is lacking. Data from ich- 

 thyoplankton surveys conducted in the western Gulf of 

 Alaska were used to examine the timing of spawning, 

 geographic distribution and abundance, and the verti- 

 cal distribution of flathead sole eggs and larvae. The 

 purpose of this study was to give a general overview of 

 flathead sole egg and larval distribution and abundance 

 in the Gulf of Alaska during the calendar year. 



Materials and methods 



The study area covered the continental shelf (approxi- 

 mately 300 m depth and less) of the western Gulf of 



Alaska from the Kenai Peninsula southwest along the 

 Alaska Peninsula to Umnak Island (Fig. 1). Also covered 

 was the east side of Kodiak Island out to the continental 

 shelf break (Fig. 1). The Alaska Stream and the Alaska 

 Coastal Current are two major surface currents that 

 flow through the study area. Both currents flow south- 

 westerly: the Alaska Stream along the shelf break and 

 the Alaska Coastal Current through Shelikof Strait 

 (Kendall et al., 1996). 



A series of ichthyoplankton surveys were conducted in 

 1972 and from 1977 to 1999 (no data were collected in 

 1980) by the Alaska Fisheries Science Center (NOAA, 

 NMFS) in the western Gulf of Alaska (Tables 1 and 

 2). Data were used from 75 surveys. Surveys were con- 

 ducted from February to November; the most intensive 

 sampling was in April and May. Not all months were 

 sampled every year, and not all cruises surveyed the 

 same area. A 60-cm diameter bongo sampler with a 

 net mesh size of 333 or 505 ;<m was towed in a double 

 oblique fashion (from the surface to near bottom and 

 back to the surface) to collect samples used to examine 

 the geographic distribution and abundance of eggs and 

 larvae. Interannual variability in the abundance of 

 eggs and larvae in the Shelikof Strait spawning area 

 can vary as much as tenfold (S. Porter, unpubl. data), 

 but to increase sampling coverage of the study area. 



