北部湾二长棘犁齿鲷生长、死亡和性成熟参数的年际变化

根据1961年～1962年(1962年)、1997年～1999年(1998年)以及2006年北部湾底拖网调查的渔业生物学资料, 对3个时期二长棘犁齿鲷(Evynnis cardinalis)的群体结构、初次性成熟体长(L50)以及生长、死亡参数等进行研究。结果表明: 1)与1962年和1998年相比, 2006年二长棘犁齿鲷的体长频率分布由双峰型转变为单峰型, 雌雄比明显增加。2)平均体长由1962年的108.8 mm减小到2006年的102.0 mm; L50由108.9 mm减小到95.9 mm; 生长系数由0.35 增加到0.50; 二长棘犁齿鲷小型化、性成熟提前和生长加快现象明显。3)对比1962年, 1998年并未发生平均体长、L50的减小, 分析认为这可能是由于这段时期二长棘犁齿鲷并未受到长时间的过度捕捞。4)3个时期的开发率分别为0.49、0.62 和0.60, 目前二长棘犁齿鲷处于过度开发状态。

Decadal changes in growth,mortality and maturity parameters of Evynnis cardinalis in Beibu Gulf

We evaluated the population structure, first maturity lengths (L50) , growth and mortality coefficient of threadfin porgy Evynnis cardinalis in Beibu Gulf using biological data obtained from bottomtrawls conducted during 1961～1962 (1962) , 1997～1999 (1998) and 2006. Results show that the bimodal patterns of length frequency distribution in 1962 and 1998 had turned into unimodal type in 2006 and the female-male ratio increased obviously; the mean body length decreased from 108.8 mm in 1962 to 102.0 mm in 2006;L50 decreased from 108.9 mm in 1962 to 95.9 mm in 2006, and growth coefficient (K) increased from 0.35 in 1962 to 0.50 in 2006, which indicates that E.cardinalis tended to be miniaturized with an increase in speed of growth and a decrease in time to mature. Slight increase in mean body length andL50 from 1962 to 1998 indicates longtime overfishing of E.cardinalis did not happened in this period. The exploitation rates (E) in 1962, 1998 and 2006 were 0.49, 0.62 and 0.60, respectively, suggesting that this stock has been over-exploited since the 1990s.