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On the optimal path of growth in chum salmon (Oncorhynchus keta) Wild, Alexander

Abstract

The effects of temperatures within the optimal range for incubation of salmon, and hyperoxic and hypoxic oxygen tensions, were examined to develop an optimal path of growth during the pre- rearing stage for chum salmon (Oncorhynchus keta). During early development, and at constant oxygen tension, an elevated temperature of 55°F (12.8°C) led to accelerated growth and most efficient conversion of yolk compared to 50°F (10°C) or 45°F (7.2°C). With increased age, growth and efficiency were favored by decreasing temperature with its associated increase in oxygen concentration and reduced metabolic demand by the embryo. After hatching, the detrimental effect of a high temperature was not offset by the increased availability of oxygen and growth was retarded relative to lower temperatures. Oxygen tensions within the treatment range of 145 to 253 mm Hg did not contribute significantly to embryo weight when measured at equal stages of development in day-degrees. The optimal path for growth with minimal mortality involved a gradual reduction in temperature from 55° to 45°F during incubation, a constant temperature of 45°F after hatching to the beginning of active feeding, and an oxygen tension not in excess of air saturation.

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