THIRTY-FOUR SPECIES OF CALIFORNIA ROCKFISHES: MATURITY 

 AND SEASONALITY OF REPRODUCTION 



Tina Wyllie Echeverriai 



ABSTRACT 



The viviparous rockfishes (Sebastes spp.) differ among species in age and size at maturity, and in the 

 timing of peal< spermatogenesis, fertihzation, and larval extrusion. Age at 50% maturity ranges from 

 2 years in S. jordani to 9 years in S. diploproa. Within species, males usually mature either at the same 

 age and size as females or at a younger age and smaller size. Rockfishes have two major seasons of lar- 

 val extrusion, winter (November-March) or spring (April-July). The reproductive season for a particular 

 species will fall within one of the major seasons throughout its geographic range. Within the major season, 

 annual variations in the peak month of larval extrusion was observed for individual species. A long 

 reproductive season and variations in the annual timing of that season are evidence of plasticity in the 

 reproductive biology of rockfishes. 



Reproductive development at the cellular level was compared with the coincident changes in the gross 

 morphology of the gonads. The resulting description of the developmental sequences of the testes and 

 ovaries enables the determination of maturity stage in the field. 



Reproductive parameters such as age and size at 

 maturity have been shown to be adaptive character- 

 istics and are responsive to external pressures. For 

 example, reduced population size due to fishing pres- 

 sure may be associated with increased growth rate, 

 reduced age at maturity, decreased fecundity, or a 

 change in the gonadal index (Adams 1980; Gunder- 

 son 1980). For haddock, Melanogrammus aeglefinis, 

 age at maturity was reduced and growth rates in- 

 creased as the fishery increased (Templeman and 

 Bishop 1979; Beacham 1983). Clupeoids shifted 

 spawning location or time, and reduced age at 

 maturity (Murphy 1977; Blaxter and Hunter 1982). 

 A study of depleted populations of Pacific mackerel, 

 Scomber japonicus, suggested a direct relationship 

 between population size and age at maturity (Par- 

 rish and MacCall 1978). Pacific halibut, Hippoglossns 

 stenolepis, stocks also showed reduced age at matur- 

 ity and increased growth rates with reduced popu- 

 lations (Schmitt and Skud 1978). Age at maturity 

 may thus be a useful indicator of heavy fishing mor- 

 tality. 



Rockfishes exhibit a variety of life history pat- 

 terns, but only a few species have been studied in 

 detail (Chen 1971; Miller and Geibel 1973; Patten 

 1973; Moulton 1977; Larson 1980; Love and West- 

 phal 1981; McClure 1982). Previously, the most com- 

 prehensive work on the maturity of rockfishes was 



^Southwest Fisheries Center Tiburon Laboratory, National 

 Marine Fisheries Service, NOAA, 3150 Paradise Drive, Tiburon, 

 CA 94920. 



by Phillips (1964) and Westrheim (1975). Phillips 

 (1964) sampled market landings from northern and 

 central California over several years. For each of 

 the 10 species he investigated, maturity was re- 

 ported for the sexes combined, and ages at matur- 

 ity were derived from back-calculated von Berta- 

 lanffy growth curves. Westrheim (1975) summarized 

 10 years of data gathered on trawl-caught fish off 

 British Columbia and the Gulf of Alaska, for which 

 he reported on size at maturity and reproductive 

 seasonality. Most of the fish in his study are com- 

 mercially important species for British Columbia 

 and, except for three species, do not occur off 

 California. 



There are some difficulties in assessing maturity 

 stages and reproductive seasonality in rockfishes. 

 One problem is the use of external morphology of 

 gonads to determine maturity stages. Some re- 

 searchers have questioned the accuracy with which 

 immature fish can be distinguished from resting, 

 mature fish during the nonreproductive months 

 (Gunderson et al. 1980; Rosenthal et al. 1982). Also, 

 the potential reproductive season may be protracted 

 and the peak time of reproduction may shift within 

 this season, so that short-term studies may be mis- 

 leading. Thus, reported variation in length and age 

 at maturity between studies could be the result of 

 uncertainty in maturity-stage determinations. 



In this study, I clarify the determination of sexual 

 maturity stages, determine age and size at sexual 

 maturity, and survey the reproductive seasonality 

 for 34 species of rockfishes from the waters off 



Manuscript accepted February 1987. 

 FISHERY BULLETIN: VOL. 85. NO. 2, 1987. 



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