DIET FEEDING RHYTHM AND GASTROINTESTINAL EVACUATION TIME OF JUVENILE CHANNEL CATFISH AND HYBRID STURGEON

A once-per-day satiation feeding (one day was divided into eight time periods, each time period was used as one treatment, the fish of each treatment was fed to apparent satiation once a day) and a continuous feeding with fixed interval (one day was divided into eight time periods, the fish of each tank was fed to apparent satiation, eight times a day) were used to investigate the diet feeding rhythm of channel catfish and hybrid sturgeon, and gastrointestinal evacuation times of the tested fish after feeding during a 24h collection period were also studied. The results showed that channel catfish exhibit a 24h diet feeding cycle and the two feeding peaks appeared at the 06:00 and 18:00 time periods, respectively under two feeding scenarios (P0.05). Hybrid sturgeon displayed a 24h diet feeding cycle and the three feeding peaks appeared at the 11:00, 17:00, and 05:00 time periods, respectively under a once-per-day satiation feeding. However, hybrid sturgeon displayed a 48h diet feeding cycle and the three feeding peaks appeared at the 11:00, 17:00 and 36:00 time periods, respectively under a continuous feeding with fixed interval. Stomach digesta ratio of channel catfish decreased sharply after a 1-9h feeding (P0.05), and it reached a minimum after the 24h feeding. But the bowel digesta ratio of the channel catfish increased sharply after a 1-9h feeding, and it achieved the maximum value after the 9h feeding and it achieved the minimum value after the 24h feeding. Stomach digesta ratio of hybrid sturgeon decreased sharply after a 1-7h feeding (P0.05), and it reached a minimum after the 24h feeding, but the bowel digesta ratio of the fish increased sharply after a 1-7h feeding and it reached the minimum value after the 24h feeding. Our results indicated that channel catfish and hybrid sturgeon exhibited the different diet feeding rhythms under two feeding scenarios, and their diet feeding rtythms were not only affected by their gastrointestinal evacuation time, but also by the different feeding time. The present results suggested that the optimal feeding period were dawn (05:00–06:00) and dusk (17:00–18:00) in cultured of juvenile channel catfish and hybrid sturgeon.