敞口池塘和遮荫池塘养殖美洲鲥当年鱼种的生长规律和差异

对600尾各生长阶段的敞口池塘和遮荫池塘养殖美洲鲥当年鱼种的体长、体质量进行了测量与分析,研究比较了两种池塘养殖鱼种生长的规律和差异。结果显示:敞口池塘和遮荫池塘养殖美洲鲥当年鱼种的体长与体质量均呈良好的幂函数增长关系(W=aL~b,R~2 0. 99,P 0. 01,n=300),b值接近且略小于3(分别为2. 786 4和2. 843 1),体长生长略快于体质量生长。养殖试验初期(0～15 d),美洲鲥当年鱼种出现飞跃式补偿生长,而后鱼种体长和体质量的特定生长率均随养殖日龄增加呈现下降趋势。敞口池塘和遮荫池塘的鱼种体长生长均可用一次线性函数(L=at+b,R~2 0. 97,P 0. 01,n=9)拟合,体质量生长均可用二次函数拟合(W=at~2+bt+c,R2 0. 97,P 0. 01,n=9);养殖前期,在57 d(9月13日)前,敞口池塘的鱼种生长优于遮荫池塘,养殖后期,在79 d(10月5日)后,则相反。敞口池塘的饵料系数(1. 22)低于遮荫池塘(2. 04)。敞口池塘鱼种体长和体质量的变异系数明显小于遮荫池塘的变异系数(P 0. 05)。研究表明美洲鲥幼鱼对高温有良好的适应能力,其高温耐受力高于成鱼。建议美洲鲥池塘养殖过程中,当年鱼种采用敞口池塘养殖,而成鱼采用遮荫池塘养殖。

Growth regularity and difference of young fish American shad Alosa sapidissima cultured in outdoor and shaded ponds

The American shad (Alosa sapidissima) is an anadromous fish species with ecological importance along the east coast of North America. At present, it has a potential for aquaculture in China because of its commercial importance and high market value. To evaluate and compare the growth regularity and difference of young fish A. sapidissima cultured in outdoor and shaded ponds, the standard length and body mass of young fish A. sapidissima (n=600) cultured in outdoor and shaded ponds were measured. The results showed:The relationship of body length and mass of young fish cultured in outdoor and shaded ponds could be described by the power function (W=aL^b, R²>0.99, P<0.01,n=300), the values b were close to and slightly less than 3 (2.786 4 and 2.843 1, respectively), and the body length grew slightly faster than the body mass. A leap-style compensatory growth reaction was found in young fish at the beginning of the culture experiment (0-15 d), and then the body length and mass specific growth rates (SGR) of young fish steadily declined with increasing culture time. The relationships between the body length of young fish cultured in outdoor and shaded ponds and culture time could be described by the linear function (L=at + b, R²>0.97, P<0.01, n=9), the intersection point of two straight lines appeared at 73.25 d (September 29); Nevertheless, the relationships between the body mass and culture time could be described by the quadratic function (W=at²+bt+ c, R²>0.97, P<0.01, n=9), the intersection point of two curves appeared at 61.92 d (September 18); at the earlier stage of culture experiment, before 57 d (September 13), young fish of outdoor pond grew faster than shaded pond; at the later stage, after 79 d (October 5), the reverse is true. The food coefficient of outdoor pond (1.22) was lower than that of shaded pond (2.04). The coefficient of variations of young fish body length and mass in outdoor pond was smaller than that of shaded pond. Therefore, the adaptive capacity for high temperature of young fish A. sapidissima is better than adult fish. It is suggested that:the young fish A. sapidissima should be cultured in outdoor pond, and then adult fish should be cultured in shaded pond.