Fishery Bulletin 90(1), 1992 



cles, hydrated oocytes, migratory nucleus oocytes, and 

 other advanced yolked oocytes. These data were ex- 

 pressed as the number of spawning states per spawner 

 (spawns per spawner, Fig. 3, lower left). The average 

 number of spawns per spawner increased from about 

 one in mid-March to about three by early April. These 

 data also indicated that spawning frequency may in- 

 crease near the end of the spawning season. 



The fraction of females with inactive ovaries that 

 were classed as postspawning also increased late in the 

 season (Fig. 3, lower right). This index can be con- 

 sidered a measure of the rate females in the popula- 

 tion pass from the active to the inactive state. Although 

 the duration of this stage was unknown, we were cer- 

 tain that it was ephemeral because there were always 

 many fewer females classed as postspawning than the 

 cumulative total of females that had passed from the 

 active to inactive state. This index increased sharply 

 in late-March through April, indicating that the rate 

 females passed into the inactive stage accelerated 

 during the last part of the season. 



The sharp increases in the three indices described in- 

 dicated that the daily production of eggs by the popula- 

 tion may be higher in March than February even 

 though fewer fish were spawning. For example, by mid- 

 March (13 March), a half to a third as many females 

 had reproductively active ovaries than in mid-February 

 (10 Feb.). On the other hand, in mid-March as compared 



with mid-February, about twice as many females with 

 active ovaries were classed as spawning, and the 

 ovaries of the spawners contained evidence of about 

 twice as many past or potential spawnings. Thus the 

 reproductive output of the reproductively active fe- 

 males in the population in mid-March might be four 

 times that of the active fish in mid-February. If this 

 is true, half the number of active females could pro- 

 duce twice as many eggs per day. This is, of course, 

 sheer speculation because the duration of these spawn- 

 ing stages is unknown. Nevertheless, the data pre- 

 sented in this section collectively suggest that the daily 

 production of eggs by the population may increase near 

 the end of the season even though fewer females are 

 spawning. 



Total fecundity 



Location of tissue samples 



A key assumption underlying the gravimetric method 

 of fecundity estimation is that oocytes are randomly 

 distributed in the ovary. To determine if advanced 

 yolked oocytes are randomly distributed in the ovary, 

 we compared the densities of advanced yolked oocytes 

 in tissue samples taken from five different locations 

 in the ovary of ten females. The location of a tissue 

 sample within the ovary was defined in terms of three 

 characteristics: longitudinal 

 plane of the ovary (anterior end, 

 middle, and posterior end); cross- 

 sectional plane (interior near the 

 lumen, exterior near the ovarian 

 wall, or interior and exterior 

 combined); and right and left 

 lobes of the ovary. The char- 

 acteristics of the five ovarian 

 locations along with the mean 

 oocyte density of each location 

 are indicated in Table 5. 



Initially we tested the overall 

 effect of location of the tissue 

 sample on oocyte density using 

 two-way ANOVA; the effect of 

 position was insignificant at the 

 5% level of significance (Table 5, 

 lower). We also tested for pos- 

 sible differences between pairs of 

 location characteristics: posterior 

 end vs. middle; posterior vs. 

 anterior ends of the ovary; right 

 vs. left lobes of the ovary; and in- 

 terior and exterior sections of the 

 ovary. No significant differences 

 were detectable between any of 



