Fecundity, Spawning, and Maturity of Female Dover Sole, Microstomus Pacificus, with an Evaluation of Assumptions and Precision

Southwest Fisheries Science Center, National Marine Fisheries Service, NOAA P.O. Box 271, La Jolla, California 92038 Fecundity, spawning, and maturity of female Dover sale Microstomus pacificus, with an evaluation of assumptions and precision 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 fecundity is determinate. More central California females had atretic advanced oocytes than Oregon females, but rates of atresia were not sufficiently high to have an important effect on the potential annual fecundity of the population. A I-kg female matured about 83,000 advanced yolked oocytes at the beginning .of the season. Vitellogenesis continued for the advanced yolked oocytes during most of the spawning season while batches were repetitively matured and spawned. About nine batches were spawned over a six-month spawning season (December-May), and spawning ceased when the standing stock of advanced oocytes was exhausted. A I-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 reproductively active. Annual reproductive effort 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 332mm total length. Various methodological issues were also treated in this paper, including validation of key assumptions underlying 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.