Feeding behaviour of hatchery-reared juveniles of the Japanese flounder following a period of starvation

The effect of starvation on feeding behaviour was studied in hatchery-reare d juveniles of the Japanese flounder in the context of improving stock enha ncement strategies. Fish (54.0 +/- 5.9 mm in total length) were deprived of food (mysids) for 1, 2, or 4 days, and their subsequent feeding behaviour was observed using a video camera. The phase of feeding action, the foragin g pattern, the off-bottom duration, and the swimming speed were defined and analyzed. The feeding action was divided into four phases: aim, creep, att ack, and return. The foraging patterns were classified into four types. The typical foraging pattern, with a single attack and a quick return to the i nitial position (type A), became less common as the fish were starved, whil e there was a greater incidence of slower returns (type B), returns to diff erent positions (type C), and multiple feeding (type D). The frequency of t he feeding action and the duration of off-bottom swimming increased as the food deprivation period increased, The swimming speed for creeping to the m ysid prey increased, but that of the return decreased as the fish were star ved. These changes in feeding behaviour under starvation may prolong the ti me flounder juveniles spend in the water column and may result in a higher risk of predation. In the stock enhancement program of Japanese flounder, s tarvation should be avoided to reduce predation and improve survival. (C) 2 000 Elsevier Science B.V. All rights reserved.