132 



Fishery Bulletin 90(1), 1992 



each year. The interval between batches is a few days. 

 The number of eggs per batch and size of eggs decrease 

 with successive batches. These patterns have been 

 observed both in Funka Bay (Sakurai 1982) and 

 Shelikof Strait (Hinckley 1990). 



Fecundity 



Miller et al. (1986) related fecundity of walleye pollock 

 from Shelikof Strait to gutted weight and fork length, 

 while Sakurai (1982) related fecundity of walleye 

 pollock from Funka Bay to whole weight and body 

 length. Conversions were applied here to the Funka 

 Bay length and weight data so fecundity could be com- 

 pared with Shelikof Strait values based on 



Y = 0.7634X + 23.4472 (r^ 0.96628, N 40) 



where X = body weight and Y = gutted weight 

 (Y. Sakurai, unpubl.); and 



Y = 1.0659X + 4.050 {r^ 0.9959, N 53) 



where X = body length and Y = fork length (T. Maeda, 

 unpubl.). 



The relative fecundity of Funka Bay fish is repre- 

 sented by the relationship F = 8.73x lO-^^L^-ss and 

 F = 106.2 Wi-21, where L = body length in mm and W 

 = body weight in grams (A^ 94) (Sakurai 1982); there- 

 fore a 300 g (gutted weight) fish produces 129,000 eggs 

 and a 1000 g fish yields 589,000 eggs. In Shelikof Strait, 

 the relationship was found to be F = 1.2604L2-2169 a,nd 

 F = 387.4551 W'oieo (N 60), where L = fork length 

 in cm and W = gutted weight in grams; this yields 

 127,000 eggs for a 300g fish and 433,000 eggs for a 

 lOOOg fish (Miller et al. 1986). Thus small fish from 

 Funka Bay have about the same number of eggs, but 

 larger fish have more eggs than those from Shelikof 

 Strait (Fig. 2). 



Eggs 



Development Eggs from Funka Bay are more vari- 

 able in size and slightly larger than those from Sheli- 

 kof Strait. In Funka Bay, eggs are 1.15-1. 68mm (i 

 1.46mm) in diameter (Nakatani and Maeda 1984, 

 T. Nakatani, unpubl.). In Shelikof Strait, egg diameter 

 ranges from 1.30 to 1.41mm, and egg size has been 

 shown to vary interannually and decrease during the 

 spawning season (Hinckley 1990). 



Eggs from Funka Bay develop at a rate dependent 

 on temperature according to the relationship 



D = 31.70 exp(-0.12T), 



where D is days to 50% hatch and T is temperature 



(°C). Thus 50% hatch times are 22.1 days at 3°C, 17.4 

 days at 5°C, and 15.4 days at 6°C (Nakatani and Maeda 

 1984). No measurements of incubation time are avail- 

 able for eggs from Shelikof Strait; however, reared 

 eggs from Auke Bay in southeast Alaska (58°20'N) re- 

 quired 19.2 days at 3°C, 14.1 days at 5°C, and 12.2 

 days at 6°C for 50% hatch (Haynes and Ignell 1983). 

 Thus eggs from southeast Alaska developed to hatching 

 more quickly, by about 2-3 days, than those from 

 Funka Bay (Fig. 3). 



Vertical distribution The vertical distribution and 

 buoyancy of eggs have been investigated in both Funka 

 Bay and Shelikof Strait. In Funka Bay, eggs rise in the 

 water column as they develop. Stage-1 (fertilization to 

 morula) eggs were found at a depth of roughly 30 m 

 (10-40 m), whereas Stage-5 (embryo more than three- 

 fourths yolk circumference) eggs were mainly at depths 

 of 10-20m (Nakatani 1988). The specific gravity of 

 Funka Bay eggs throughout development was within 

 a range of 1.020-1. 025 g/cm^ (x 1.0226g/cm3). This 

 resulted in an upward velocity of 4.9 m/h in ambient 

 water through the homogenized water column early in 

 the spawning season (o' 26.41-27.17), and is consis- 

 tent with field observations of shallower depths for 

 older eggs compared with those recently spawned 

 (Nakatani and Maeda 1984, Nakatani 1988). 



In Shelikof Strait, the vertical distribution of eggs 

 changes during development in response to their 

 changing specific gravity. Newly spawned eggs are 

 positively buoyant, and thus rise from the deep loca- 

 tions where they are spawned. In middle stages of 

 development, the eggs become heavier and sink until 

 just before hatching when they again rise toward the 

 surface (Kendall and Kim 1989). The specific gravity 



