FISHERY BULLETIN: VOL. 85, NO. 2 



that occur off California (Moser and Ahlstrom 1978; 

 Richardson and Laroche 1979; Laroche and Richard- 

 son 1980, 1981; Anderson 1983); the difficulties of 

 differentiating between similar species are evident 

 in these studies. Knowledge of the principal month 

 of parturition may be a useful tool when identify- 

 ing species in the age population. Principal month 

 of parturition would have to be documented for the 

 year that recruitment is investigated. 



Life history parameters that are interrelated, such 

 as growth, maturity, and fecundity, can be influ- 

 enced by external conditions, such as temperature, 

 prey abundance, and predation (Stearns and Cran- 

 dall 1984). The manner in which they can be affected 

 is species-specific and may change in a predictable 

 manner. Observed changes that coincide with re- 

 duced population sizes include increase in growth 

 rates (Templeman and Bishop 1979), decrease in age 

 at maturity (Murphy 1977; Parrish and MacCall 

 1978; Schmitt and Skud 1978; Templeman and 

 Bishop 1979), and decrease in size at maturity (Aim 

 1959; Pitt 1975). Stearns and Crandall (1984) pro- 

 posed that changes in age and/or size at maturity 

 are determined by genetic as well as environmental 

 factors, so that populations will respond in a predict- 

 able manner. A shift in either the age or size at 

 maturity in Sebastes may be an indication of a 

 change in population densities. In order to detect 

 any population changes, age and size at maturity 

 for species should be determined yearly and within 

 a well-defined geographic area. Fish of the esti- 

 mated age and size at first maturity should be 

 included— sampling from market fish tends to yield 

 only mature fish. Ages should be determined from 

 the same fish that are sampled for maturity. 



Fecundity in poikilotherms is generally related to 

 size; changes in growth rates and size at maturity 

 will affect fecundity. Fecundity often relates more 

 to body size in short-lived species and to available 

 energy in long-lived species (Ware 1980). Fecundity 

 increases with size in at least some species of Sebas- 

 tes (Phillips 1964), but annual reproductive success 

 may be linked to available energy. Gonad volumes 

 of female S. flavidus were reported for 1981 (Guille- 

 mot et al. 1985) and compared with volumes mea- 

 sured during the El Nifio winter of 1983-84 (Lenarz 

 and Wyllie Echeverria 1986); this comparison 

 showed reduced gonad volumes in 5. flavidus for the 

 1983 reproductive season. Whether the decreased 

 gonad volume was due to egg size or number was 

 not determined. 



Shifts in age and/or size at maturity may occur 

 in species that have a multigenerational, late-matur- 

 ing population. In his studies of flatfish populations. 



Roff (1982) predicted that size at maturity would be 

 primarily influenced by size-dependent mortality and 

 that changes in size at maturity would occur in 

 species where growth to a minimal size is more adap- 

 tive than early reproduction. Changes in age at 

 maturity will more likely occur in species that 

 mature early. Changes in size, rather than age, at 

 maturity would most likely occur in Sebastes sub- 

 jected to overfishing or long-term environmental 

 stress. 



General changes in life history parameters may 

 be predictable according to a species' position on the 

 r-/iC selection continuum. Increased fishing mortality 

 resulting in decreased populations may affect life 

 history parameters by increasing growth rates, re- 

 ducing age at first maturity, increasing fecundity 

 at age (Adams 1980; Gunderson 1980), and reducing 

 variability in the gene pool by reducing the number 

 of spawning groups in the more /C-selected species 

 (Leaman and Beamish 1984). The reproductive 

 strategy of Sebastes reflects more A'-type character- 

 istics, which include later maturity, slower growth 

 rates, lower individual fecundity, or some degree of 

 parental care (Garrod and Horwood 1984). The K- 

 type reproductive strategy enables a species to 

 minimize the effects of a poor reproductive year 

 (Roff 1984). A disadvantage for a heavily fished K- 

 type species is the late age at maturity, as exists 

 in Sebastes, so that the advantage of many reproduc- 

 tive seasons must be balanced against adult popu- 

 lation size to obtain an allowable harvest. 



The reproductive strategy of Sebastes, with multi- 

 ple generations reproducing simultaneously and the 

 plasticity of annual timing, results in a buffered 

 system. The populations of exploited stocks of 

 Sebastes should be able to recover from a single year 

 of high mortality due either to poor recruitment or 

 to adult mortality. However, overfished populations 

 or long periods of poor recruitment could result in 

 a reduced size at maturity and a corresponding re- 

 duced fecundity. 



ACKNOWLEDGMENTS 



Among the many people who contributed to this 

 research, I wish to thank the biologists and seasonal 

 samplers of the California Department of Fish and 

 Game, the personnel who assisted me in the collec- 

 tion and processing of these samples, including but 

 not limited to Lisa Andrade, Todd Anderson, 

 Patrick Guillemot, Steven Pace, Dana Tryde, 

 Mickey Singer, Stuart Running, Marianne McKean, 

 Karen Novak, Sonia Linnik, Michael King, Sally 

 Krenn, Lisa Natanson, Kathleen Mathews, Laura 



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