26 



Fishery Bulletin 105(1) 



atretric eggs in the ovary by length category is shown 

 in Figure 6C. Average number of batches correspond- 

 ing to potential and realized fecundity are shown in 

 Figure 6D. 



The average fork length for females during the 1994 

 NMFS survey was 40 cm (Lowe and Fritz, 1994). Po- 

 tential fecundity (stage 5-1-) was estimated to be 41,994 

 eggs, and realized annual fecundity was estimated to 

 be 30,664 eggs for a 40-cm female (Table 2). Batch 

 fecundity for a 40-cm female was estimated to be 6689 

 eggs and the number of batches spawned showed no 

 statistically significant relationship with length for 

 both potential (P=0.35) and realized (P=0.75) fecun- 

 dity (Fig. 6D). The estimated number of batches pro- 

 duced annually per female was calculated by using the 

 grand mean and standard deviation for all specimens 

 combined. The average number of batches of eggs for 

 potential and realized fecundity was estimated at 6.1 

 and 4.5 batches per year, respectively, with corre- 

 sponding 95% confidence intervals of ±2.64 and ±2.21 

 batches. This result would indicate that the average 

 female has the potential to spawn about 6 batches, 

 but may reabsorb 1-2 batches of eggs at the end of 

 the season. 



Discussion 



The reproductive strategy of Atka mackerel and other 

 hexagrammids has been characterized by low fecun- 

 dity and large eggs, high parental care, and by larvae 

 hatched at an advanced stage of development (Gorbu- 

 nova, 1962). Potential fecundity for an average female 



Atka mackerel of 40 cm was 41,994 eggs for oocytes 

 at stage 5+ and is higher than the estimates for Kam- 

 chatkan waters by Gorbunova (1962), who gave a range 

 between 5000 and 31,000 eggs for a 52-cm female. Zolo- 

 tov (1993) estimated potential fecundity to be 38,700 

 eggs (vitelline oocytes plus hydrated oocytes in first 

 batch) off Kamchatka, which is also slightly lower than 

 our estimate. Our batch fecundity estimate of 6689 eggs 

 for an average female of 40 cm is similar to Zolotov's 

 (1993) estimate of 6930 for a fish of the same size. 



Atka mackerel are characterized by a continuous size 

 distribution of oocytes much like that of indeterminate 

 spawners. However, Atka mackerel have a distinct 

 spawning season (July-October) during which they 

 spawn batches containing a large number of eggs (Zo- 

 lotov, 1993; McDermott and Lowe, 1997). This spawn- 

 ing pattern differs from that of typical indeterminate 

 spawners that spawn a small number of eggs (in rela- 

 tion to the total number present) almost continuously 

 for many months, as characterized by the northern 

 anchovy (Engraulis mordax) (Hunter et al., 1985). 

 Atka mackerel seem to lie somewhere in the middle of 

 determinate versus indeterminate spawning fish. It 

 appears that there is a potential to develop and spawn 

 up to seven batches if all stage-4 oocytes are devel- 

 oped and spawned. Most of the stage-4 oocytes still 

 remaining in the ovary during the spawning phase 

 probably constitute the pool of oocytes to be spawned 

 in the next season. However, those oocytes could be a 

 reserve to be developed and spawned in highly produc- 

 tive years (i.e., during favorable spawning conditions). 

 Estimates of fecundity based on oocytes at stage 5-i- 

 may be conservative if some of the stage-4 oocytes are 



