循环水养殖条件下水温对大菱鲆氨氮排泄、转氨酶及免疫因子的影响

Effects of water temperature on the nitrogenous excretion,transaminase and immune factors of turbot( scophthatmus maximus) in recirculating aquaculture system

在高密度工业化封闭循环海水养殖条件下（养殖密度为14.2±0.48 kg／m^2），选取大菱鲆（371.68±43.15 g）360尾，随机均分4组，设置4个水温梯度14℃、16℃、18℃和21℃，旨在探寻水温对大菱鲆氨氮排泄、转氨酶及血清免疫因子的影响，试验期为56 d。结果表明：（1）养殖水体总氨氮浓度随水温升高呈先升后降，18℃时总氨氮浓度极显著高于14℃、21℃时；大菱鲆氨氮排泄率随水温升高而升高，且二者呈指数关系。（2）大菱鲆肝脏GPT、GOT活力随水温升高呈先升后降，均在18℃达最大值；而血清两种指标变化趋势与之相反，均在21℃达最大值。（3）血清LZM、SOD活力及皮质醇含量均随水温升高呈先升后降，均在18℃达最大值；血氨含量则逐渐下降，14℃时极显著高于18℃、21℃时；鳃丝Na^＋-K^＋-ATPase活力随水温升高而升高，但组间差异不显著。综上，封闭循环水养殖大菱鲆的适宜水温为16～18℃。

Four groups of juvenile turbots （371.68±43.15 g） were selected randomly to be reared at four constant water temperatures （ 14℃, 16℃, 18℃ and 21℃） , to examine the effect of the temperature on nitrogenous excretion, transaminase and serum immune factors of turbots in high stocking density （ 14. 20 ± 0.48 kg/m2 ） of closed recirculating aquaculture system for 56 days. The results indicated that： 1） The concentration of total ammonia nitrogen （ TAN） in water increased firstly and decreased as temperature increased, TAN of group 18℃was significantly higher than that of group 14 ℃and 21 ℃; nitrogenous excretion increased as temperature increased, described as an exponential function;2） The activities of GPT and GOT in liver increased firstly and decreased with increasing temperature. GPT and GOT of group 18℃ were highest. A reverse trend was found for GPT and GOT in serum, the maximum both occurred at group 21℃;3） The activities of LZM and SOD and Cortisol levels all increased firstly and decreased with increasing temperature, and the maximum all occurred at group 18℃. Ammonia levels decreased gradually as temperature increased, and the levels of group 14℃ were significantly higher than that of group 18 ℃ and 21℃. The activity of Na^＋-K^＋-ATPase increased gradually as temperature increased, but the differences among groups were not significant. It is concluded that the optimal water temperature of turbot in closed RAS was 16？18℃, providing the basis and reference for water temperature regulation of turbot in closed recirculating mariculture system.