浙南近海凤鲚时空分布及生物学分析

Spatio⁃temporal distribution and biological analysis of Coilia mystus in the coastal waters of south Zhejiang

凤鲚(Coilia mystus)作为浙南近海的经济鱼类之一,近年来,由于长期的过度捕捞,其数量迅速下降。为探究浙南近海凤鲚资源的变动情况及其生物参数,2020年5月至2021年1月对浙南近海21个调查站位进行4个航次的底拖网调查,以生物量、丰度作为资源分布的数量指标,采用ELEFANⅡ技术和Beverton⁃Holt动态综合模型对凤鲚的生长和死亡参数进行估算并分析凤鲚资源变动趋势。结果表明:4个航次共采集凤鲚903尾,总出现率为52.4%,生物量和丰度最高值出现在夏季,分别为24.46 kg/km^(2)和2.33×10^(3)ind./km^(2);体长范围为43~224 mm,优势体长组为100~180 mm,占全年总数的84.81%,体长(L)和体重(W)的关系式为W=1.25×10^(-6)L3.2693(R^(2)=0.9448);体重的生长拐点年龄为1.20 a。采用Pauly经验公式估算出凤鲚的自然死亡系数为0.75,采用长度变换渔获曲线法估算凤鲚的总死亡系数为3.06,捕捞死亡系数为2.31,当前开发率为0.76。Beverton⁃Holt动态综合模型显示,浙南近海凤鲚已处于过度开发状态。为有效保护并恢复浙南近海凤鲚资源,建议设立凤鲚种质资源保护区,加强对凤鲚产卵场、仔稚鱼保育场的保护。

As one of the economic fish species in the coastal waters of southern Zhejiang,Coilia mustus is being long⁃term overfished which has led its quantity to a rapid decline in recent year.To determine the the resources changes and bi⁃ological parameters of Coilia mystus in the coastal waters of south Zhejiang,four bottom trawl voyages were conducted at 21 stations from May 2020 to January 2021.The catch per unit effort method was used to estimate the biomass distribu⁃tion of C.mystus,the biological parameters of C.mystus were calculated using FiSAT II(Version 1.2.2),and the Be⁃verton⁃Holt model was constructed to evaluate the resource changes.The results showed that a total of 903 C.mystus were collected in 4 bottom trawling surveys.The frequency of C.mystus at all stations was 52.4%.The body length of C.mystus ranged from 43 to 224 mm,and the dominant body length was between 100 to 180 mm with a proportion of 84.81%.The relationship equation of body length and weight of C.mystus was W=1.25×10^(-6)L3.2693(R^(2)=0.9448).The weight growth inflection age was 1.20a.Natural mortality coefficient M was estimated as 0.75.The fishing mortali⁃ty coefficient(F)was equal to 2.31(F=Z-M=2.31).The exploitation rate was assessed as 0.76.The two⁃dimen⁃sional analysis showed that the exploitation of C.mystus in the coastal of south Zhejiang has been fully utilized.There⁃fore,it is recommended to establish a spawning ground reserve in the waters between Jiaojiang River estuary and Oujiang River estuary to protect and restore the resources of C.mystus.