北部湾花斑蛇鲻生物学特征的演化

Evolution of biological characteristics of Saurida undosquamis(Richardson) in the Beibu Gulf,South China Sea

根据1959-1960年、1992-1993年、1997-1999年和2009-2010年北部湾底拖网渔业资源调查的生物学资料,对花斑蛇鲻(Saurida undosquamis)群体组成、生长和生殖力参数等生活史特征进行了研究。结果表明,花斑蛇鲻的平均体长从1959-1960年的185.5 mm下降到1992-1993年的163.1 mm、1997-1999年的133.2 mm和2009-2010年的130.5 mm,相应地平均体质量分别为66.5 g、46.4 g、23.8 g和22.6 g。1959-1960年、1992-1993年、1997-1999年和2009-2010年间的Von Bertanaffy生长方程的渐近体长(L)、生长参数(k)和理论初始年龄(t0)分别为497.8 mm,0.26,-0.49;424.1 mm,0.28,-0.48;385.3 mm,0.33,-0.41和342.5 mm,0.39,-0.36。体质量拐点年龄(tr)分别从1959-1960年的4.05龄提前到1992-1993年的3.66龄、1997-1999年3.05龄和2009-2010年2.43龄。50%性成熟体长(L50)则从1959-1960年111.2 mm下降到1992-1993年的105.2 mm、1997-1999年的95.6 mm和2009-2010年的96.7 mm。对于同一体长组,当前花斑蛇鲻的个体相对生殖力比20世纪60年代上升了56.4%。花斑蛇鲻种群生活史特征参数的一系列变化表明,在捕捞引起进化背景下,北部湾花斑蛇鲻种群产生了适应性进化反应,种群明显趋向小型化和低龄化,生长速度加快,性成熟提前。

We evaluated the population structure,growth and fecundity of Saurida undosquamis（Richardson） in the Beibu Gulf using biological data obtained from bottom trawls conducted during 1959-1960,1992-1993,1997-1999 and 2009-2010.The mean body length of S.undosquamis decreased from 185.5 mm in 1959-1960 to 163.1 mm in 1992-1993,133.2 mm in 1997-1999,and 130.5 mm in 2009-2010.Similarly,mean body weight decreased from 66.5 g in 1959-1960 to 46.4 g in 1992-1993,23.8 g in 1997-1999,and 22.6 g in 2009-2010.The asymptotic length（L∞）,growth coefficient（k）,and zero-length age（t0） in the von Bertanaffy growth equation during the periods 1959-1960,1992-1993,1997-1999,and 2009-2010 were 497.8 mm,0.26,-0.49;424.1 mm,0.28,-0.48;385.3 mm,0.33,-0.41,and 342.5 mm,0.39,-0.36,respectively.The inflexion age of body weight decreased from 4.05 years between 1959-1960 to 3.66 years between 1992-1993,3.05 years in 1997,and 2.43 years between 2009-2010.Body length at 50% sexual maturity（L50） decreased from 111.2 mm between 1959-1960 to 105.2 mm between 1992-1993,95.6 mm between 1997-1999,and 96.7 mm between 2009-2010.For the same body length,the current individual relative fecundity of S.undosquamis increased by 56.4% com-pared to the early 1960s.The changes in the life history traits of S.undosquamis in the Beibu Gulf during the last five decades suggest that the stock has undergone fishing-induced evolution（FIE）,characterized by miniaturiza-tion,an increase in the speed of growth,and a decrease in time to maturity.