By William R. Heard
Animal Behaviour, Volume 12, Issues 2-3, April-July 1964, Pages 382-388, ISSN 0003-3472, DOI: 10.1016/0003-3472(64)90029-6.

A fry trap designed to study the behaviour of emerging sockeye salmon fry in Brooks River, Alaska, during the spring of 1961 revealed the following: 1. 1. The initial emergence of sockeye salmon, fry from natal gravels was basically nocturnal. Evidence is presented that suggests initial daylight emergence may exceed daylight downstream migration of fry.2. 2. The minimum duration of sockeye salmon fry emergence from twelve 4-square-foot gravel areas ranged from 37 to 48 days and averaged 41 days.3. 3. Nocturnal emergence was retarded and daylight emergence was accelerated when nursery gravels were exposed to artificial light at night. The over-all rate of emergence was retarded during periods of continuous light. This decrease was followed by a strong resurgence of nocturnal emergence on the first night of normal darkness after the experimentally lighted nights.

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