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A study of the principal spawning grounds and of the spawning of the lemon sole, Parophrys vetulus (Girard), in the Gulf of Georgia in relation to the commercial fishery Taylor, Frederick Henry Carlyle

Abstract

The winter fishery for lemon sole in the gulf of Georgia depends on populations spawning in Baynes sound and Boat harbour from January to March. The peak period in 1946 was from January 24 to February 23 in Baynes sound and 10 days earlier in Boat harbour. Although some spawning took place throughout the whole of both regions, with the exception of Porlier pass, spawning was more intense in certain areas of each region. Minimum estimates of fishing intensities of 42% and 26.3% for the Baynes sound and Boat harbour regions respectively appear too heavy to maintain the fishery at its present level. During the 1947 fishing season Baynes sound was largely closed to trawling; in Boat harbour the percentage tag recovery was 6.3% as compared to 18.8% for the same period in 1946. These recoveries indicated an average annual increase in length of 7.3% or in weight of 21.9%. Lemon sole spawning in Baynes sound dispersed to parts of the gulf north of Nanoose bay, while those spawning in Boat harbour dispersed southward as far as the American boundary. Although these two populations do not mix to an appreciable extent, their composition is very similar except for a larger number of immature and small mature fish in Baynes sound. The Porlier pass population, consisting of two-thirds immature fish differed markedly. An estimate of the amount of population change on the spawning grounds was made by comparing the variations in tag returns per period calculated on the basis of a constant number of tagged fish available and a constant weight of fish caught each period. Stomach analysis showed that lemon sole do not feed actively during the winter and that fully matured fish feed less actively than- immature or spent individuals. Worms, clams, and brittlestars formed the principal foods.

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