Daily “predawn” peak of locomotion in fish

摘要: Abstract Bluegill and largemouth bass held under alternating, 12-hour periods of light “darkness” (very dim light) fed daily at the onset show a predawn peak locomotion. The appeared between tenth twentieth days when fish became active during last 1 to 3 hours “dark” period. When feeding were shifted 6 later time day, delayed small amount day for 4 restore its original relation light. advanced an earlier reappeared in 2 days. Six-hour shifts or failed cause corresponding peak. both hours, as though alone had been altered. A locomotion persisted constant without days, then disappeared periodicities illumination resumed. conclusion is discussed that regulated from within by internal rhythm which itself co-ordinated change