Effects Of Water Current On Swimming Performance And Active Metabolism In Juvenile Hybrid Sturgeon And GIFT Strain Nile Tilapia

Indoor experiments,using a special designed device at 26(±0.5)℃,were conducted to investigate the effects of water velocity on swimming performance and active metabolism of Hybrid Sturgeon(Huso duricus Georgi♂×Acipenser schrencki Brandt♀)(56.12±4.95g)and GIFT strain Nile tilapia(Oreochromis niloticus)(83.16±5.45g),aiming to provide data for fish factory's culturation.The results were as follows:1.The effects of water current on swimming performance of juvenile Hybrid Sturgeon and GIFT strain Nile tilapiaWhen water current increased,the time of swimming forward of Juvenile Hybrid Sturgeon decreased,whereas the time of swimming backwards increased.While GIFT strain Nile tilapia mostly keep stationary at each water velocity.Below the water current of 0.5 m·s^-1,rheotactic frequency and tail beat frequency(TBF) of Juvenile Hybrid Sturgeon and GIFT strain Nile tilapia increased with increasing water current.When water velocity was up to 0.5 m·s^-1,tail beat frequency decreased.2.The effects of water current on metabolism of juvenile Hybrid Sturgeon and GIFT strain Nile tilapia.Oxygen cumpution rate(OCR) in Juvenile Hybrid Sturgeon increased with increasing water velocity.OCR was linearly correlated both with rheotactic frequency and tail beat frequency.In the 24 hours continuous observation,OCR of Hybrid sturgeon increased with time before the first 9h,while OCR in 0.5 m·s^-1 decreased after then.OCR in GIFT strain Nile tilapia increased with increasing water velocity,with the maximum at 0.3 m·s^-1 and the minimum at 0 m·s^-1.But it decreased under the water current velocity of 0.5 m·s^-1.OCR of 0.3 and 0.5 m·s^-1 were significantly higher than those of 0.0 and 0.1m/s.3.The effects of water current on oxygen nitrogen ratios of juvenile Hybrid Sturgeon and GIFT strain Nile tilapiaThe oxygen nitrogen ratios of Juvenile Hybrid Sturgeon fluctuated at different water velocities,with the maximum at 0.3 m·s^-1 and the minimum at 0.5 m·s^-1.The primary energy substrate was protein and fat when the water velocity reached 0.0,0.1 or 0.5 m·s^-1.The carbohydrate and fat were the primary energy substrate at 0.3 m·s^-1.The oxygen nitrogen ratios of juvenile GIFT strain Nile tilapia fluctuated between11.94～29.53,with the maximum at 0.3 m·s^-1 and the minimum at 0.5 m·s^-1.The primary energy substrate was protein and fat at different water current.