Variation in Growth of Dover Soles and English Soles as Related to Upwelling

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Abstract
Variations in growth rates of Dover sole (Microstomus pacificus) off Astoria and Brookings, and of English sole (Parophrys vetulus) off Astoria and Coos Bay, Oregon were studied by means of increments between annuli on scales and interoperculum bones for Dover and English sole, respectively. Age‐specific growth rates of both species were statistically different among years. The maximum variation for Dover sole was 19% of the mean growth rate for the period 1958–1975. English sole growth varied as much as 17% from the mean growth between 1961 and 1974. Dover and English sole showed the same good or poor years for growth simultaneously among all locations. The growth increments were significantly greater for Dover sole captured off Astoria than for Dover sole captured off Brookings. There were no significant growth differences for English sole by location. Dover sole off Astoria had a general long‐term increase in growth rate between 1958 and 1966 followed by a gradual decrease through 1969. Large fluctuations in the rate occurred through the mid‐1970s. A similar long‐term trend occurred for English sole but was less apparent due to the shorter time series of data. The growing season for English sole begins in March and probably extends through September. The most rapid growth occurs during May and June. For these months annual variations in a continental shelf temperature index are significantly and negatively correlated with annual fluctuations in growth increments of both species. Although variations in the May and June upwelling index were not significantly correlated with annual fluctuations in growth, long‐term trends of these two factors appear to be related. Growth does not seem to be associated with stock density changes.

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