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Fishery Bulletin 88(3). 1990 



Figure 5A 



Relationship between mean diameter of a batch of walleye 

 pollock eggs spawned in the laboratory, and the mean stan- 

 dard length of larvae at yolksac absorption. 



Figure 5B 



Relationship between mean dry weight of a liateh of 

 walleye pollock eggs spawned in the laboratory, and the 

 mean standard length of larvae at yolksac absorption. 



val between batches of eggs spawned in Atlantic cod 

 Gadus m,orhua (Kjesbu 1988). 



Egg size variation within and among females 



The laboratory studies showed that egg diameter in 

 walleye pollock declined significantly over the spawn- 

 ing period of an individual. This was also shown by 

 Sakurai (1982) for walleye pollock (over a limited por- 

 tion of the spawning cycle) and for other gadoids by 

 Hislop et al. 1978 and Moksness and Vestergard 1982 

 (Melanogrammus aeglefinus), by Grauman 1965 and 

 Solemdal 1970 (Gadus morhua), and Hislop 1975 (Mer- 

 langius meriangus). The amount of decrease seen in 

 walleye pollock, about 12%, was comparable with that 

 seen in Gadus morhua by Kjesbu (1988) (7-15%) and 

 with that in Merlangius meriangus by Hislop (1975) 

 (9-14%). This decline may represent an adaptation by 

 the parent stock to conditions faced by the larvae, as 

 discussed later in this section. 



Egg size in walleye pollock does not appear to be cor- 

 related with female length. The measurement of eggs 

 from the first batch spawned (a method also used by 

 Kjesbu (1988) for Gadus morhua) removes variation in 

 egg size caused by the decline in egg size over the 

 course of the spawning cycle, a problem which may 

 have confused the results of other studies of the rela- 

 tionship between egg size and female size. Egg size in 

 walleye pollock did not appear to correlate with female 

 age or condition. Wet weights of body, gonad, and liver 

 are not particularly sensitive indicators of condition in 

 fish, however, and use of these measures may have 

 obscured a correlation between these indices and egg 

 size. 



There are many contradictory studies on the egg size- 

 female size relationship. Sakurai (1982, Theragra chal- 

 cogramyna). Marsh (1984, Etheostomxi specfahilis), 

 Zilstra (1973, Clupea harengus). Solemdal (1970, Gadus 

 morhua) and Ossthuizen and Daan (1974, G. morhua), 

 and others did not find egg size-female size or age 



