Effects of food availability on temporal activity patterns and growth of Atlantic salmon

摘要: 1. Patterns of sheltering and activity are fundamental importance in the ecology animals determining interactions among predators prey. Balancing decreased mortality risk when with increased feeding rate exposed is believed to be a key determinant diel patterns many animals. 2. Despite lower foraging efficiency at night than during day, Atlantic salmon Salmo salar parr nocturnal winter low summer temperatures. Nocturnal also occurs warm water temperatures summer, but little known about functional significance this behaviour. 3. This study aimed determine: (1) preferred shelter pattern months, (2) their response variations food availability balancing growth (G) (M), as expressed through time out shelter. We differentiated four potential responses reduced availability: no response; G decreases M remains constant; (3) constant increases; (4) increases. 4. Time from was inversely related availability. Fish subject high were significantly less active day those restricted rations. However, had significant effect on extent which fish night. There evidence variation 5. Salmon predominantly ration levels, consistent previously reported behaviour winter. Rather switching diurnal per se, supposed, it appears that only needed sustain rate, depends 6. modulate amount they rather responding over an order magnitude.