Reproduction of darkblotched rockfish off the oregon coast

Seasonal reproductive development, size and age at sexual maturity, and fecundity were described for darkblotched rockfish Sebastes crameri collected off the Oregon coast. Altogether. 1,060 fish captured by commercial groundfish and shrimp trawlers between July 1986 and July 1987 were examined. Reproductive events were protracted. Insemination of females occurred from August to December, and fertilization and parturition followed from December through March. Spermatozoa were observed within both vitellogenic and previtellogenic ovaries between July and November. Reproductive events in smaller males and females were delayed relative to those in larger individuals. Females attained 50% maturity at a greater size (36.5 cm total length) and age (8.4 years) than males (29.6 cm total length; 5.1 years). The unimodal development of eggs and larvae indicated one parturition per year. Most age-6, age-7, and age-8 females possessed ovaries in an intermediate “maturing” condition. Histological analysis revealed that most of these females were immature: ovaries showed no evidence of previous spawning, oocytes never developed beyond an early vitellogenic stage, and during months of parturition, many of these females were resorbing their advancing oocytes. Total fecundities ranged from 19,815 to 489.064 oocytes per ovary pair and increased exponentially with increasing fish length, linearly with fish weight, and asymptotically with fish age (6 to 66 years).