The Relative Strengths of Whitefish Year Classes as Affected by Egg Plantings and Weather

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Abstract
Over the period 1941-1950 a total of 13,062 whitefish has been collected in small annual samples from each of seven Alberta lakes. The lakes lie between 53[degree] and 56[degree] North latitude and 110[degree] and 116[degree] longitude; they range in size from 12 to nearly 500 square miles in area. The ages of the fish were detd. from their scales and the data used to determine the relative strengths of the year classes of 1935-1945 (in a few cases, to 1947). The relative strengths are compared to the hatchery record; it is shown that hatchery plantings have had no effect on year class strengths; e.g., unsupported year classes are, in several instances, stronger than supported ones. In six of the lakes a remarkable similarity in the variation of the year classes was observed; thus year classes were weak in 1935-36, strong from 1937-40, and generally weaker in 1941, 42 and 43. Somewhat limited data on temperatures, precipitation and winds were studied; no conclusive findings were made but there is a reasonable suggestion that year class strength may be inversely correlated with strength of winds in September, October and November.

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