为调查军曹鱼生长和氮收支与温度和体质量的关系,采用鱼类生物能量学的原理和方法,开展了不同温度(21、27和33 ℃)和体质量(10、20、50和100 g)对军曹鱼生长和氮收支的影响研究,并建立了生长——温度/体质量关系及不同温度和体质量条件下的氮收支方程。结果显示:(1)温度和体质量对军曹鱼生长影响显著,且两者之间存在交互作用。军曹鱼在实验的最高水温(33 ℃)及最小体质量(10 g)时生长最快,在实验的最低水温(21 ℃)及最大体质量(100 g)时生长最慢。(2)实验的体质量范围内,军曹鱼特定生长率均随水温升高呈显著增长趋势;在实验的温度范围内,军曹鱼特定生长率随体质量增加呈减速下降趋势,两者间的关系采用幂函数定量描述。多元回归分析表明,模型LnSGR=a bLnW cT dT2 eTLnW能较好地拟合军曹鱼特定生长率、温度及体质量间的关系。(3)军曹鱼摄食氮、排粪氮、排泄氮和生长氮受温度和体质量影响显著,随温度升高而增加,随体质量增加趋于减少。(4)不同温度和体质量组军曹鱼氮收支方程存在差异,且温度对氮收支方程的影响大于体质量。对同一体质量组,水温27和33 ℃时生长氮占食物氮的比例明显高于水温21 ℃时,而水温27和33 ℃时代谢氮占食物氮的比例则明显低于水温21 ℃时;对同一温度组,军曹鱼氮收支方程变幅较小。(5)在所有氮收支方程中,摄食氮用于排泄的比例大于68%。研究表明,在实验的温度和体质量范围内,环境温度偏低不利于军曹鱼生长;排泄是军曹鱼氮支出的最主要途径;水温27~33 ℃时军曹鱼氮收支方程相对恒定。
In order to investigate the relationships among growth,nitrogen budget,water temperature and fish size of cobia,by using the principles and methods of fish bioenergetics,a laboratory experiment was carried out to study the effects of water temperature(21,27 and 33 ℃)and fish size(about 10,20,50 and 100 g)on growth and nitrogen budget,and furthermore,the growth models in relation to water temperature and fish size and the nitrogen budgets at different temperature and size treatments were established in this paper.The results showed that:(1)Growth of cobia was affected significantly by water temperature and fish size as well as their interaction.The fastest growth rate occurred for cobia with initial body weight about 10 g at 33 ℃ and the lowest growth rate occurred for cobia with initial body weight about 100 g at 21 ℃ within the experimental temperature and size ranges.(2)In a given size group for cobia,SGR increased with temperature.At a given temperature,SGR decreased with fish size,and the relationships between SGR and W could be described as power functions for cobia.By using multiple regression analysis,the model,LnSGR=a bLnW cT dT2 eTLnW,provided a good fit to the data of specific growth rate(SGR),water temperature(T)and fish size(W).(3)Within the experimental water temperature and body size weight ranges,food nitrogen,feces nitrogen,excretion nitrogen and growth nitrogen of cobia were influenced significantly by water temperature and fish size,and increased with temperature but decreased with fish size.(4)Nitrogen budgets differed as water temperature and fish size changed,and were more sensitive to water temperature than to fish size.In a given size group the proportion of food nitrogen allocated to growth at 27 and 33 ℃ was much higher than that at 21 ℃,but contrary to the proportion of food nitrogen lost in excretion.At a given temperature the variation of nitrogen budgets among different size groups was small.(5)More than 68% of food nitrogen was lost