Abstract.- The potential annual 

 fecundity of Dover sole becomes fixed 

 before the spawning season when the 

 average diameter of the advanced 

 stock of yolked oocytes exceeds 0.86 

 mm; hence potential annual fecun- 

 dity is determinate. More central 

 California females had atretic ad- 

 vanced oocytes than Oregon females, 

 but rates of atresia were not suffi- 

 ciently high to have an important ef- 

 fect on the potential annual fecundity 

 of the population. A 1-kg female ma- 

 tured about 83,000 advanced yolked 

 oocytes at the beginning pf the sea- 

 son. Vitellogenesis continued for the 

 advanced yolked oocytes during most 

 of the spawning season whUe batches 

 were repetitively matured and 

 spawned. About nine batches were 

 spawned over a six-month spawning 

 season (December-May), and spawn- 

 ing ceased when the standing stock 

 of advanced oocytes was exhausted. 

 A 1-kg female released about 10,000 

 eggs per spawning, except for the 

 first and last batches which were 

 smaller than the rest. Near the end 

 of the season, females may spawn 

 more frequently than earlier in the 

 year, increasing the daily production 

 of eggs by the population even 

 though fewer females are reproduc- 

 tively active. Annual reproductive ef- 

 fort of Dover sole was equivalent to 

 about 14% of body wet weight per 

 year. Fifty percent of the females 

 had become sexually mature when 

 they reached 332 mm total length. 

 Various methodological issues were 

 also treated in this paper, including 

 validation of key assumptions under- 

 lying estimates of annual fecundity; 

 fecundity sample-size requirements; 

 evaluation of criteria and bias in 

 estimating female sexual maturity; 

 and comparisons of classification by 

 histology and gross anatomy. 



Fecundity, spawning, and 

 maturity of female Dover sole 

 Microstomus pacificus, with an 

 evaluation of assumptions 

 and precision 



J. Roe Hunter 

 Beverly J. Macewjcz 

 N. Chyan-huei Lo 

 Carol A. Kimbrell 



Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA 

 P,0. Box 271, La Jolla, California 92038 



Manuscript accepted 15 January 1992. 

 Fishery Bulletin, U.S. 90:101-128 (1992). 



Fecundity and sexual maturity esti- 

 mates are staples of fishery science. 

 Inevitably, they will be estimated for 

 every species of economic conse- 

 quence because of their importance 

 in the dynamics of the population. A 

 second reason for studying fecundity 

 is that when fecundity estimates are 

 combined with estimates of the abun- 

 dance of eggs in the sea, they can be 

 used to estimate the biomass of a 

 stock. Our laboratory is currently 

 evaluating such ichthyoplankton me- 

 thods for estimating the biomass of 

 Dover sole Microstomus pacificus, a 

 large demersal resource occurring 

 along the upper continental slope of 

 the west coast of North America. The 

 fecundity of Dover sole from Oregon 

 has been estimated (Yoklavich and 

 Pikitch 1989), but no estimate exists 

 for the segment of the stock living in 

 central California waters, nor have 

 the assumptions underlying fecun- 

 dity and sexual maturity assessments 

 been studied with the thoroughness 

 necessary for accurate estimates of 

 adult biomass. Thorough analysis of 

 these assumptions is usually lacking 

 in the fecundity literature. 



Our objectives were to describe the 

 reproduction of Dover sole off central 

 California and Oregon, and evaluate 

 the assumptions underlying fecun- 

 dity and sexual maturity estimates. 



We describe changes in the reproduc- 

 tive state of female Dover sole dur- 

 ing the spawning season, estimate 

 annual fecundity, batch fecundity, 

 rates of atresia, annual rates of 

 spawning, and length at 50% mature 

 (ML,5o). 



Evaluation of the assumptions under- 

 lying annual fecundity estimates re- 

 quires defining six fecundity terms, 

 and those underlying maturity esti- 

 mates require defining four terms for 

 reproductive state. 



Fecundity 



Annual fecundity Total number of 

 eggs spawned by a female per year. 



Total fecundity Standing stock of 

 advanced yolked oocytes. 



Potential annual fecundity Total 

 advanced yolked oocytes matured per 

 year, uncorrected for atretic losses. 

 In species with determinate fecun- 

 dity, potential annual fecundity is 

 considered to be equivalent to the 

 total fecundity prior to the onset of 

 spawning. 



Determinate fecundity Annual 

 fecundity is determinate when the 

 potential annual fecundity becomes 

 fixed prior to the onset of spawning. 

 In fishes with determinate fecundity, 

 total fecundity decreases with each 



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