661 



Abstract— Variation in the life history 

 parameters of Dover sole (Microstonuis 

 pacificus) off the coasts of Washington, 

 Oregon, and northern California was 

 investigated by using research survey 

 data. We compared growth, maturation, 

 and length-weight cuives of Dover sole 

 within the International North Pacific 

 Fisheries Commission (INPFC) statis- 

 tical areas of Monterey, Eureka, Colum- 

 bia, and Vancouver We found strong 

 evidence of dimorphism in growth and 

 maturation rates between sexes. In 

 addition, geographic variation in both 

 growth and maturation rates was also 

 suggested. Male and female Dover sole 

 from the Columbia area had lower Brody 

 growth coefficients and larger asymp- 

 totic lengths than Dover sole from other 

 areas. Further, there was an apparent 

 latitudinal cline in maturation rates 

 because males and females matured 

 at smaller size and younger ages at 

 higher latitudes. In contrast, no differ- 

 ence between male and female length- 

 weight relationships was detected. In 

 comparison with other pleuronectids, 

 we found that Dover sole matured at 

 relatively larger sizes and younger ages. 

 These differences likely reflect adapta- 

 tion of Dover sole to the inherent vari- 

 abilitv of the California Current. 



Variation in life history parameters of Dover sole. 

 Microstomas pacificus, off the coasts of 

 Washington, Oregon, and northern California 



Jon Brodziak 



Hatfield Marine Science Center 



Northwest Fisheries Science Center 



National Marine Fisheries Service, NOAA 



2030 SE Marine Science Drive 



Newport, Oregon 97365 



Present address; Northeast Fisheries Science Center 



166 Water Street 



Woods Hole, Massachusetts 02543 

 E mail address Jon 8rodzlak@noaa.gov 



Robert Mikus 



Hatfield Marine Science Center 

 Oregon Department of Fish and Wildlife 

 2040 SE Marine Science Dnve 

 Newport, Oregon 97365 



Manuscript accepted 15 March 2000. 

 Fish. Bull. 98:661-673 (2000). 



Dover sole {Mici-osloiuus pacificus) is 

 a deep-water pleuronectid fish that 

 ranges from Baja, California, to the 

 Bering Sea (Hart, 1973) at depths from 

 10 m to 1200 m (Pearcy et al., 1982; 

 Allen and Smith, 1988). Dover sole are 

 demersal and have a complex life his- 

 tory that includes an extended pelagic 

 larval phase of one year or more ( Pearcy 

 et al, 1977; Markle et al., 1992; Toole 

 et al., 1993; Butler et al.. 1996) and 

 an ontogenetic migration range from 

 continental shelf to continental slope 

 (Jacobson and Hunter, 1993). Dover 

 sole support an important commercial 

 fishery off the coasts of Washington, 

 Oregon, and California, where annual 

 landings have averaged about 12,000 t 

 during 1956-96 (Brodziak et al, 1997). 

 Previous research on life history 

 parameters of Dover sole off the west 

 coast of the United States was con- 

 ducted during the late 1940s and 

 the 1980s. Hagerman (1952) estimated 

 growth, maturation rates, and length- 

 weight curves of Dover sole from com- 

 mercial fishery samples collected from 

 the ports of Eureka and Fort Bragg, Cal- 

 ifornia during 1948-49. Harry (1959) 

 estimated maturation rates of Dover 

 sole from commercial fishery samples 

 collected at the port of Astoria, Oregon, 

 during 1948-49. More recently. Hunter 



et al. (1990) have estimated growth 

 and maturation rates of Dover sole 

 from research survey samples collected 

 between Point Conception and Half 

 Moon Bay, California, during 1985-88. 

 Hunter et al. (1992) refined matura- 

 tion rate estimates of female Dover sole 

 through histological analysis of sui^ey 

 data collected off the coasts of Oregon 

 and California during 198.5-89. 



In this study, we investigated varia- 

 tion in life history parameters of Dover 

 sole off the coasts of Washington, Oregon, 

 and northern California from samples 

 collected duiing research surveys during 

 1984-85 and 1990-93. Dover sole sam- 

 ples were partitioned into geographic 

 regions based on International North 

 Pacific Fisheries Commission statistical 

 areas in order to investigate latitudinal 

 differences among potential manage- 

 ment units. We used length-at-age data to 

 estimate growth and to quantify sexual 

 dimorphism and geographic variation in 

 growth. Maturation of male and female 

 Dover sole as a function of length and 

 age was estimated and geographic varia- 

 tion in maturity was quantified. Sexual 

 dimorphism and geographic variation on 

 weight at length were also explored. We 

 discuss apparent differences between life 

 history parameters of Dover sole and 

 other pleuronectids. 



