中西太平洋金枪鱼围网流木鱼群中鲣鱼种群结构分析

Stock structure of skipjack tuna (Katsuwonus pelamis) from the log school by purse seine in the Western and Central Pacific Ocean

鲣鱼（Katsuwonus pelamis）是金枪鱼围网的主要目标鱼种，研究其生物学特性有助于了解其群体结构，对于合理利用该资源具有重要意义。根据2006年10月-2007年2月及2007年10月-2008年1月在海上测定的975尾捕获自流木鱼群的鲣鱼生物学数据，应用统计与回归等分析方法对这些鲣鱼的叉长组成、又长与体质量关系、性比、性腺成熟度等基本生物学特性进行了分析。结果表明：1）叉长组成：流木鱼群中鲣鱼的叉长组成不呈正态分布（P〈0．05），叉长范围为243～733mm，优势叉长组为302～500mm，占80．62％，其中雌、雄个体叉长分布存在显著性差异（t=3．106，P〈0．05）；2）叉长与体质量关系：流木鱼群鲣鱼的叉长（FL）与体质量（aM）关系为BW=6．0983×10^-6FL^3.1800（R^2=0．9618），雌鱼和雄鱼的叉长与体质量关系之间不存在显著性差异（ANCOVA，F=2．756，P〉0．05）；3）性比：在351—400mm（x^2=7．784，P〈0．05）和401～450mm（x^2=17．147。P〈0．05）2个体长组中，雌雄性比存在显著性差异；流木鱼群鲣鱼的平均雌雄性比约为1：0．83，且存在显著性差异（x^2=5．878，P〈0．05）；4）性腺成熟度：流木鱼群鲣鱼的性成熟度以Ⅳ期以下为主，占84．11％，计算得出的达到首次性成熟的雌鱼和雄鱼叉长分别为520．62和527．52mm，均大于实际观测的达到性成熟的最小叉长。

Skipjack tuna （Katsuwonus pelamis） is one of the main target species of tuna purse seine fishery. The study of its biological characteristics will help the better understanding of its stock structure, and have significance to the reasonable utilization of the resource. Based on the observation data of 975 skipjack tuna from the log school sampled on board purse seine vessels operated in the Western and Central Pacific Ocean waters from October 2006 to February 2007 and from October 2007 to January 2008, the basic biological characteristics such as fork length （FL）, mass （BM）, FL-BM relationship, sex ratio, and gonad maturity stage were analyzed by power regression and other statistic methods. The results indicated that the fork length distribution of the skipjack tuna did not follow normal distribution （P 〈 0. 05 ）. The fork length was from 243 to 733 mm, and the dominant one was from 302 to 500 mm, accounting for 80.62% of the total sampled fish. There was significant difference （t = 3. 106, P 〉 0. 05 ） in the FL distribution between females and males. The FL-BM relationship could be described as BM = 6. 0983 × 10^ -6 FL^3.1870（ R^2 = 0. 9618）, and no significant difference was found in such a relationship between females and males （ ANCOVA, F = 2. 756, P 〉 0. 05）. There existed significant difference in the female-male ratio between the fork length sets from 351 to 400 mm （X^2 =7.784, P 〈0. 05） and from 401 to 450 mm （X^2 = 17. 147, P 〈 0. 05 ）. The average female-male ratio of the skipjack tuna was about 1 ： 0. 83, and also showed significant difference （X^2 = 5. 878, P 〈 0. 05 ）. The gonad maturity of the skipjack tuna was dominant by the maturity stages of Ⅳ and lower, accounted for 84. 11% of the total number of sampled fish, and the estimated sizes at first maturity of female and male skipjack tuna were 520.62 and 527.52 mm, respectively, being higher than the observed minimum maturity sizes.