KENDALL ET AL.: GROWTH OF LARVAL WALLEYE POLLOCK 



week of April. Incubation time for walleye pollock 

 eggs held at 5°-6°C in the laboratory is estimated 

 to be 14 days (Haynes and Ignell 1983; Nakatani 

 and Maeda 1984; Nishimura and Yamada 1984); 

 spawning of walleye pollock occurs primarily in 

 late March and early April in Shelikof Strait 

 (Dunn et al. fn. 5), supporting our estimated 

 hatching dates distribution. 



DISCUSSION 



Relative Abundance of Eggs 

 and Larvae 



Neuston collections in spring in the northern 

 Gulf of Alaska have been reported only for 1978, 

 mainly over the shelf, south and east of Kodiak 

 Island, a month earlier than the present study 

 (Kendall and Dunn 1985). Eggs of Theragra 

 chalcogramma were most abundant; the rest of 

 the identified eggs were of several pleuronectids. 

 The greater abundance of T. chalcogramma in 

 relation to the pleuronectids in the earlier cruise, 

 when compared with the present data (Fig. 5), 

 probably reflects the seasonal difference in 

 spawning times. Pleuronectids spawn mainly in 

 late spring and early summer in the Gulf of 

 Alaska while T. chalcogramma is mainly a late 

 winter-early spring spawner (Kendall and Dunn 

 1985). 



Eggs have been reported from bongo catches 

 from three other cruises in the northern Gulf of 

 Alaska in May (Bates and Clark 1983^0. Kendall 

 and Dunn 1985); eggs of pleuronectids and those 

 of T. chalcogramma were most abundant. How- 

 ever, the rank order of abundance of the various 

 pleuronectids varied considerably among the 

 cruises. Usually eggs of Glyptocephalus zachirus, 

 Hippoglossoides elassodon, and Microstomas 

 pacificus were among the five most abundant 

 taxa. 



Among larvae in the neuston tows during the 

 present study, mainly spring spawning taxa (e.g., 

 Ammodytes hexapterus, Bathymaster spp., T. 

 chalcogramma) were represented; whereas lar- 

 vae of fall-winter spawning taxa (e.g., three hexa- 

 grammids, and Hemilepidotus spp. [Irish lords]) 

 were abundant during the earlier cruise (Kendall 

 and Dunn 1985). 



In bongo catches during other May cruises in 



lOBates, R. D.,andJ.Clark. 1983. Ichthyoplankton off Ko- 

 diak Island and the Alaska Peninsula during spring 

 1981. U.S. Dep. Commer., Natl. Mar. Fish. Serv., NOAA, 

 NWAFC Proc. Rep. 83-09, 105 p. 



the area, larvae of T. chalcogramma, Hippoglos- 

 soides elassodon, Bathymaster spp., and A. 

 hexapterus have always occurred frequently, as in 

 the present study (Bates and Clark fn. 9; Kendall 

 and Dunn 1985). 



Distribution of 

 Walleye Pollock Eggs 



The few eggs collected during the present study 

 represented a very late part of the spawning, 

 which occurs in Shelikof Strait mainly in early 

 April (Dunn et al. fn. 5) (Fig. 1). Recently hatched 

 larvae (<5 mm SL), which were collected during 

 our survey (Fig. 2), also indicate prolonged 

 spawning but probably at a low level after mid- 

 April. The eggs we found were mainly over the 

 deep waters at the southwest end of Shelikof 

 Strait, and it would be expected that they were 

 also farther to the northeast. This is the same 

 area of occurrence of eggs during the height of 

 spawning (Dunn et al. fn. 5), indicating that the 

 adults spawn mainly in Shelikof Strait through- 

 out this period, although individual spawning 

 fish probably migrate in and out of the area. 



Comparisons of Distribution of 

 Walleye Pollock Larvae 



In 1981, several sequential cruises to Shelikof 

 Strait mapped a large concentration of walleye 

 pollock eggs in early April; and in late April and 

 again in mid-May, a concentration of larvae was 

 found progressively further to the southwest of 

 the area where the eggs had been (Bates and 

 Clark fn. 10) (Fig. 1). The size of the larvae in the 

 concentration increased between the cruises. 



Sampling in 1981 and 1982 for walleye pollock 

 larvae was at the same area and time (24-28 May) 

 as the present study (Dunn et. al. fn. 5). Compari- 

 sons of distribution, abundance, and size of the 

 larvae among these 3 years reveal remarkable 

 differences (Table 6). Spawning time in 1981, 

 based on ages of eggs caught in early April, and 

 presence of newly hatched larvae in late April, 

 centered around 5-8 April. In 1983, based on 

 birthdate distributions presented here, modal 

 spawning time was also in the second week of 

 April. Sampling in subsequent years has shown a 

 remarkable consistency in spawning place and 

 time (Kendall unpubl. data). By 24-28 May the 

 patch of larvae in 1981 and 1983 had drifted to 

 the same area, just north of Sutwik Island (Figs. 



517 



