672 



Fishery Bulletin 98(4) 



those of our study because of differences in sampling and 

 maturation criteria, they suggest, however, the possibility 

 that female size at maturity may have declined since the 

 1950s. 



We found no difference between male and female length- 

 weight curves. Male and female length-weight curves were 

 virtually identical for fish less than 50 cm in length. 

 Comparisons between large mature females (>50 cm) and 

 males were not possible because maximum observed size 

 of male Dover sole is about 51 cm. In addition, some 

 geographic variation in length-weight relationships was 

 detected. Estimated length exponents from the allonietric 

 equation exceeded 3 for all INPFC areas, with the excep- 

 tion of the Vancouver area, where relatively few samples 

 were collected. Overall, it appeared that Dover sole weight 

 during late autumn, when samples were collected, was not 

 proportional to the cube of fish length. In contrast, Hager- 

 man (1952) found that Dover sole weight was roughly 

 proportional to the cube of length in commercial fishery 

 samples collected throughout the year. Hagerman's esti- 

 mates may not be comparable to ours owing to differences 

 in sampling and analysis. We recommend year-round col- 

 lection of Dover sole samples for length-weight analysis 

 to determine whether seasonal and geographic variation 

 are important in predicting mean weight at length in the 

 population. 



In comparison with other pleuronectids, we found that 

 Dover sole matured at relatively larger sizes and younger 

 ages. Beverton (1992) reported average ratios of L-q/L., of 

 0.47 and 0.52 for male and female pleuronectids, whereas 

 comparable values in our study were 0.56 and 0.64. Sim- 

 ilarly, male and female ratios of A^g/A^^^^^. of 0.28 and 

 0.39 from Beverton (1992) were higher than correspond- 

 ing values of 0.12 and 0.17 in our study. Observed dif- 

 ferences with other pleuronectids likely result from the 

 complex life history pattern of Dover sole in the California 

 Current. Dover sole are a relatively late-maturing flatfish. 

 The age at first reproduction (a) that maximizes expected 

 lifetime fecundity for this species is roughly a=15 years, 

 where a=log( 1+(3A7M))/A' (see Roff, 1991) using A'=0.091 

 for females from our study and a natural mortality rate 

 of M=0.09/yr (Brodziak et al., 1997). In contrast, observed 

 ages at first reproduction for Dover sole range from 4 

 to 6 years (Castillo, 1995), or roughly 1/3 of the optimal 

 age that would maximize fitness. However, these equilib- 

 rium calculations do not account for environmental forc- 

 ing, and differences between the optimal and obsei-ved 

 values probably reflect the importance of environmental 

 variation (Roff 1982) on the reproductive success of Dover 

 sole. It may be necessary for Dover sole to reproduce as 

 soon as possible to hedge their bets against natural cycling 

 in the sui-vival of pelagic lai-vae in the California Current 

 (Parrish et al., 1981). In comparison to the pleuronectids 

 reviewed in Beverton (1992), the lower Ar,nM„,,^^ ratio of 

 Dover sole may reflect the lack of growth experienced by 

 adults that inhabit the oxygen minimum zone. Similarly, 

 Dover sole may have a higher A-,/L . ratio than other 

 pleuronectids because they achieve most of their poten- 

 tial growth as juveniles while resident on the continental 

 shelf Overall, maturation rates of Dover sole appear to 



differ from other pleuronectids and we believe that these 

 differences reflect adaptation of Dover sole to the inherent 

 variability of the California Current. 



Acknowledgments 



We thank the Captains, crew, and scientific staff of the FV 

 Marathon, the FV Mys. Babiishkiua, the RV Miller Free- 

 man, the ¥V Posey don, and the MV Half Moon Bay for col- 

 lecting the samples used in our study We thank Richard 

 Methot and three anonymous reviewers for their helpful 

 comments on the draft manuscript. We also thank Mark 

 Saelens of the Oregon Department of Fish and Wildlife 

 (ODFW) and Marion Mann, Joseph O'Malley, and Bruce 

 Pederson of the ODFW and National Marine Fisheries 

 Sei-vice Cooperative Ageing Project for their support and 

 assistance in aging Dover sole. This work was partially 

 supported by Grants NA37FN0063 and NA67FN0174 from 

 the National Marine Fisheries Service of the National 

 Oceanic and Atmospheric Administration to the Oregon 

 Department of Fish and Wildlife. 



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