养殖美洲鲥的生长特性

通过对各周年生长阶段的养殖美洲鲥(Alosa sapidissima)体长、体重的测量与分析,研究了工厂化养殖美洲鲥的周年生长特性。养殖美洲鲥雌雄鱼的体长与体重关系均呈幂函数增长相关,其方程分别为,雌:W=0.8062×10~(-5) L~(3.1113)(n=122,R~2=0.997 5,P0.01);雄:W=1.0047×10~(-5) L~(3.0574)(n=125,R~2=0.997 5,P0.01),b均接近于3,呈等速生长;雌雄鱼生长均可分快速生长期(0~+龄)、稳定生长期(1~+龄)、生长衰老期(2~+龄)三个时期,雌鱼生长快于雄鱼。拟合出von Bertallanffy生长方程,雌:Lt=467.92(1﹣e~(-0.5748(t+0.1710))),Wt=1637.72(1﹣e~(-0.5748(t+0.1710)))~(3.1113);雄:Lt=389.21(1﹣e~(-0.7374(t+0.1975))),Wt=834.08(1﹣e~(-0.7374(t+0.7189)))~(3.0574)。雌雄鱼体重生长拐点分别位于1.517 8 a和1.224 7 a,属性成熟拐点,拐点前生长较快;拐点后,特别是性成熟后(2龄),2~+龄鱼的生长速度明显降低;同时,2龄鱼繁殖季节过后会出现大量死亡。建议商业化工厂化养殖美洲鲥以2龄前上市为宜。

Growth Characteristics of Cultured American Shad Alosa sapidissima

The American Shad (Alosa sapidissima) is an anadromous fish species with ecological importance on the east coast of North America.At present,it has a potential for aquaculture in China due to its commercial importance and high market value.To evaluate and determine growth characteristics of A.sapidissima,we measured the standard length and body weight of industrially cultured A.sapidissima (n =217) (the basic culture conditions were shown in Table 1).The results showed:The relationships between body length and weight could be described by the power function:W =0.8062 × 10-5L3.1113 (n =122,R2 =0.997 5,P ＜ 0.01) for female (♀);W =1.0047 × 10-5L3.0574 (n =125,R2 =0.997 5,P ＜ 0.01) for male (♂) (Fig.1),those values b all were closed to 3,this means an isometric growth;There were three stages in the growth of female and male (Table 2):Fast growth stage (0+ age),the specific growth rates of body length (SL) and body weight (Sw) were 63.54％/a-165.49％/a and 512.37％/a-519.15 ％/a,respectively;Steady growth stage (1 + age),the St and Sw were 44.85％/a-48.05％/a and 110.15％/a-126.48％/a,respectively;Aging growth stage (2+ age),the SL and Sw were 4.13％/a-10.29％/a and 32.16％/a-61.30％/a,respectively.The condition factors of 0-age and 2-age fish were significantly lower (P ＜ 0.05) than that of 1-age and 3-age fish (Table 2).From the beginning of 2-age,the condition factors of female were significantly higher (P ＜ 0.05) than that of male (Table 2).The females grew faster than the males.The growth of intensively cultured A.sapidissima was in a constant speed which can be described with yon Bertalanffy equation:Lt =467.92 (1-e-0.5748 (t+ 0.1710)) (♀),Lt =389.21 (1-e-0.7374(t+0.1975)) (♂) (Fig.2);Wt =1637.72 (1-e-0.5748(t+0.1710))31113 (♀),Wt =834.08 (1-e-0.7374 (t + 0.7189))3.0574 (♂) (Fig.3).According to the growth,the body length growth rate equations of female and male were dL/dt =268.96 e-0.5748 (t +0.1710) (♀),and dL/dt =287.00 e-0.7374 (t + 0.1975) (♂),respectively (Fig.4);the body weight growth rate equations of female and male were dW/dt =2928.86 e-0.5748 (t + 0.1710) (1-e-0.5748 (t + 0.1710))2.1113 (♀),and dW/dt =1880.46e-0.7374 (t + 0.1975) (1-e-0.7374 (t + 0.1975))2.0574 (♂),respectively (Fig.5);the acceleration growth rate equations for body weight of female and male were d2W/dt2 =1683.51 e-0.5748 (t + 0.1710) (1-e-0.5748 (t + 0.1710))1.1113(3.1113 e-0.5748 (t+ 0.1710)-1) (♀),and d2W/dt2 =1386.65 e-0.7374 (t + 0.1975) (1-c-0.7374 (t + 0.1975))1.057a(3.0574 e-0.7374 (t + 0.1975)-1) (♂),respectively (Fig.6).The inflection points on body weight growth curve of female and male were 1.517 8 a and 1.224 7 a,respectively (Fig.6);They belonged to the inflection points of sexual maturity.Before inflection point,growth was faster;After inflection point,especially after sexual maturity (2 age),the growth rate of the 2+ age fish was decreased obviously;Meanwhile,after the breeding season,the 2-age fish die largely.Therefore,2-age A.sapidissima should be sold in the commercialization industrial aquaculture.