THE EFFECTS OF FEEDING TIME ON ACTIVITY LEVELS AND RHYTHMS OF HYBRID TILAPIA

A 6d trial with Videomex2V image motion monitor systemwas conducted to investigate the activity levels and rhythms inhybrid tilapia ( Oreochromis niloticus ♀×O. aureus ♂) on different feeding times. The trial was carried out in a self2circulationsystem consisting of 36 organic glass tanks (28cm ×24cm ×20cm,water 10 —12cm deep). The monitor light period was from8:00 —19:00 and the dark period from20:00 —7:00,and two hours were spent to adjust image motion monitor systemfrom7:00to 8: 00 and 19: 00 to 20: 00. During the experiment, dissolved oxygen was maintained above 5. 53mg/ L, ammonia below011025mg/ L and temperature 25 ℃.The fish were deprived of diet for one day at the beginning of the experiment,and then individual fish was randomly select2ed,batch2weighed and allocated into each tank. The 36 tanks were divided into 4 groups and each group contained 9 tanks select2ed randomly. The fish were fed twice a day and the feeding time was 8:00 + 14:00,14:00 + 20:00,20:00 + 2:00 and 2:00 +8:00 individually (expressed by S1,S2,S3 and S4 individually),and uneaten feed was collected 60 min after feeding.The results showed that the diet weights per body weight were significantly lower in groups S1 and S2 than in groups S3 andS4,and S1 and S2 were similar,S3 and S4 being,too;Activity rhythms,not swimming distance and time per day,were affectedsignificantly by feeding time,and S1 had more similar activity rhythms to S2,and S3 had more similar activity rhythms to S4.