Influence of water temperature and feeding rate on ammonia excretion of juvenile black rockfish Sebastes schlegelii

Abstract

An experiment was conducted to determine the effects of water temperature and feeding rate on daily pattern and rate of total ammonia nitrogen (TAN) in juvenile Korean rockfish Sebastes schlegelii (mean body weight 15.0 ± 1.2 g). Fish were acclimated over 4 weeks under three different water temperatures (12 and 26℃) and three feeding rates (0.5, 1.0 and 1.5% of body weight at 12℃ and 1.0, 2.0 and 3.0% of body weight at 26℃). Fish were hand-fed with a commercial diet (protein 45.1%) at one time daily (09:00 hour) in recirculating system with 18 culture chambers. After feeding of each rate, water was sampled for both the inlet and outlet of each chamber every 3 hours over a 24-h period to investigate post-prandial TAN excretion pattern. The post-prandial TAN excretion increased with the increase of water temperature under all feeding rates. Mean post-prandial TAN excretion rates of fish in 0.5, 1.0 and 1.5% feeding rate at 12℃ were 7.0, 13.9 and 20.3 mg TAN kg fish-1 h-1, respectively. Mean post-prandial TAN excretion rates of fish in 1.0, 2.0 and 3.0% feeding rate at 26℃ were 13.0, 25.7, 43.4 mg TAN kg fish-1 h-1, respectively. The peak post-prandial TAN excretion rate occurred after 6 hours after feeding in all water temperature and feeding rate conditions. Mean peak post-prandial TAN excretion rates of fish in 0.5, 1.0 and 1.5% feeding rate at 12℃ were 12.6, 19.7 and 43.1 mg TAN kg fish-1 h-1, respectively. M acclimated over 4 weeks under three different water temperatures (12 and 26℃) and three feeding rates (0.5, 1.0 and 1.5% of body weight at 12℃ and 1.0, 2.0 and 3.0% of body weight at 26℃). Fish were hand-fed with a commercial diet (protein 45.1%) at one time daily (09:00 hour) in recirculating system with 18 culture chambers. After feeding of each rate, water was sampled for both the inlet and outlet of each chamber every 3 hours over a 24-h period to investigate post-prandial TAN excretion pattern. The post-prandial TAN excretion increased with the increase of water temperature under all feeding rates. Mean post-prandial TAN excretion rates of fish in 0.5, 1.0 and 1.5% feeding rate at 12℃ were 7.0, 13.9 and 20.3 mg TAN kg fish-1 h-1, respectively. Mean post-prandial TAN excretion rates of fish in 1.0, 2.0 and 3.0% feeding rate at 26℃ were 13.0, 25.7, 43.4 mg TAN kg fish-1 h-1, respectively. The peak post-prandial TAN excretion rate occurred after 6 hours after feeding in all water temperature and feeding rate conditions. Mean peak post-prandial TAN excretion rates of fish in 0.5, 1.0 and 1.5% feeding rate at 12℃ were 12.6, 19.7 and 43.1 mg TAN kg fish-1 h-1, respectively. M