中西太平洋金枪鱼围网鲣鱼起水鱼群种群结构分析

ANALYSIS ON STOCK STRUCTURE OF FREE SWIMMING SKIPJACK TUNA (KATSUWONUS PELAMIS) SCHOOL CAUGHT BY CHINA TUNA PURSE SEINE IN THE WESTERN AND CENTRAL PACIFIC OCEAN

根据2006年10月—2007年2月及2007年10月—2008年1月在中西太平洋海域测定的1343尾由金枪鱼围网捕获的起水鱼群的鲣鱼生物学数据,应用统计与回归的分析方法对鲣鱼的叉长组成、叉长和体重关系、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)起水鱼群鲣鱼的叉长范围为243～746 mm,优势叉长组为401～600 mm,占到88.24%,其中雌、雄个体叉长组成呈显著性差异(x2=843.7,P<0.01);(2)起水鱼群鲣鱼的叉长(FL)与体重(W)的关系为W=6.3905×10-6FL3.1938(R2=0.9443),且叉长与体重的关系并不因性别而存在显著性差异(ANCOVA,F=0.549,P>0.05);(3)起水鱼群鲣鱼的平均雌雄性比约为1∶0.95,但在501～550 mm(x2=4.00,P<0.05)和651～700 mm(x2=4.17,P<0.05)2个体长组中,雌雄性别比例不符合"1∶1"的理论期望;(4)起水鱼群鲣鱼的性成熟度以Ⅳ期(28.93%)和Ⅴ期(43.67%)为主,计算得出的雌鱼和雄鱼的首次性成熟叉长分别为473.15 mm和440.78 mm,均大于实际观测到的达到性成熟的鲣鱼的最小叉长。本次调查研究得出了"在调查水域鲣鱼的起水鱼群是以性成熟的成鱼为主的群体"的初步结论。

Based on 1343 skipjack tuna from the free 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,biological characteristics such as fork length（FL）,weight（W）,FL-W relationship,sex ratio,and gonad maturity stages were collected and analyzed by power regression and other statistic methods.The results indicate： 1） The fork lengths of skipjack caught in the fishery were found to range from 243 to 746mm,with the dominant fork lengths of 401 to 600 mm accounting for 88.24% of the total sampled fish.There was significant difference（x^2= 843.7,P〈0.01） in the FL composition between females and males;2） The FL-W relationship could be described as W=6.0983 10-6 FL3.1870（R^2=0.9443）,and no significant difference was found in such a relationship between body weight and sex（ANCOVA,F=0.549,P〈0.05）.3） The average male-female ratio was 1∶0.95,but sex ratio showed significant changes with fork length from 501 to 550mm（x^2=4.00,P〈0.05） and from 651 to 700 mm（x^2=4.17,P〈0.05）.4） Maturity of the skipjack gonad sampled in the fishery were dominant by individuals with maturity stages Ⅳ（28.93%） and Ⅴ（43.67%）,and the estimated minimum sizes of female and male skipjack at maturity were 473.15 mm and 440.78 mm,respectively.Both estimates were higher than the sizes observed at sea.The preliminary conclusion of the investigation was that adult fishes with maturity were dominant in the population of skipjack from free swimming in our survey waters.