不同光周期条件对罗非鱼生长及性腺发育的影响

Effects of different photoperiod conditions on the growth and gonad development of tilapia

【目的】筛选出适宜尼罗罗非鱼生长及性腺发育成熟的最适光周期,为其工厂化养殖生产提供科学依据。【方法】以雌性尼罗罗非鱼为研究对象,设12 L∶12 D、14 L∶10 D、16 L∶8 D和18 L∶6 D 4个不同的光周期,饲养30 d后比较分析不同光周期条件下尼罗罗非鱼生长阶段的形态指标、体内激素水平及性腺发育差异情况。【结果】尼罗罗非鱼的相对增重率随光照时间的延长呈先降后升再降的变化趋势,在16 L∶8 D光周期条件下达最大值;体长相对增长率随光照时间的延长整体上呈下降趋势,而体宽和体高的相对增长率随光照时间的延长呈不同程度的上升趋势。尼罗罗非鱼血清中促性腺激素释放激素(GnRH)、雌二醇(E2)和褪黑素(MT)3种激素含量随光照时间的延长均呈上升趋势,且在18 L∶6 D光周期条件下达最大值。适当延长光照时间能有效促进尼罗罗非鱼性腺发育,在16 L∶8 D光照周期条件下促进作用最强,而在18 L∶6 D光照周期下其性腺发育受抑制。【结论】16 L∶8 D是尼罗罗非鱼生长及性腺发育的最适光周期,在实际生产中适当延长光照时间可提高罗非鱼产量并促进其性腺发育成熟。

【Objective】In this study,the optimal photoperiod of growth and gonadal maturation for tilapia was selected.The results provided scientific basis for tilapia breeding.【Method】In this study,female Nile tilapia was studied,four photoperiod conditions of 12 L∶12 D,14 L∶10 D,16 L∶8 D and 18 L∶6 D were designed,and the morphological indexes,serum hormones and gonad development were analyzed after feeding for 30 d.【Result】The relative weight gain rate of Nile tilapia was decreased at the beginning,then increased with the increase of photoperiod,which was the largest in the 16 L∶8 D.The relative growth rate of body length was decreased with the increase of light duration.The relative growth rate of body width and relative growth rate of body height increased with the increase of photoperiod.The levels of gonadotropin-releasing hormone(GnRH),estradiol(E2)and melatonin(MT)in Nile tilapia serum increased with the extension of photoperiod,which were the largest in the 18 L∶6 D photoperiod.The results showed that prolongation of photoperiod could effectively promote gonadal development in Nile tilapia,and the effect was the best in the photoperiod of16 L∶8 D,but inhibited in the photoperiod of 18 L∶6 D.【Conclusion】The 16 L/8 D photoperiod condition is the optimal illumination condition for the growth and gonad development of Nile tilapia.Prolonging photoperiod increases the yield of Nile tilapia and promotes the maturation of gonads in actual production.