Effect of varying temperature regimes on the development of pink salmon (Oncorhynchus gorbuscha) eggs and alevins

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Abstract
Eggs and alevins from six odd-year, brood-line stocks of pink salmon (Oncorhynchus gorbuscha) spawning in southern British Columbia were incubated under varying temperature regimes and subjected to rapid temperature changes at specific developmental stages. Increasing or decreasing temperature regimes had no significant effect on egg and alevin survival. The inclusion of 2 or 4 °C in the temperature regime reduced egg survival. Rapid temperature changes from 12 to 1 °C late in development reduced alevin survival when compared with transfers from 8 to 1 °C. Hatching and emergence time varied inversely with mean incubation temperature. Decreasing temperature regimes produced longer and heavier alevins and fry than increasing temperature regimes. Low mean incubation temperatures from fertilization to fry emergence resulted in longer and heavier alevins and fry than those at higher mean temperature. Transfers from 8 or 12 °C to 1 °C early in development had a greater effect on alevin length and weight than transfers late in development. Temperature regimes can be manipulated to enhance survival, control development time, and increase alevin and fry size.