热带大西洋与热带太平洋拟锥齿鲨生物学特征比较

拟锥齿鲨(Pseudocarcharias kamoharai)是金枪鱼延绳钓渔业中较常见的兼捕物种。它处于海洋生态结构的顶端,对海洋生态系统的稳定和多样性起着非常重要的作用。根据我国金枪鱼渔业国家观察员2011~2015年在热带大西洋海域(6.38°S~15.17°N、42.02°W~18.53°W)调查时采集的1 426 ind拟锥齿鲨和2006~2015年在热带太平洋海域(16.88°S~10.85°N、148.71°E~96.80°W)调查时采集的1 037 ind拟锥齿鲨,按不同性别对其生物学特征进行初步研究和比较。结果表明:热带太平洋、热带大西洋两海域拟锥齿鲨雄性和雌性之间在平均叉长、优势叉长方面均存在显著性差异(P0.05),热带太平洋海域的拟锥齿鲨优势叉长和平均叉长值更大;两洋区雄性和雌性拟锥齿鲨叉长与全重关系均存在显著性差异(P0.05);两洋区拟锥齿鲨的雌雄性比分别为1∶0.80和1∶1.71,具显著性差异(P0.05);在拟锥齿鲨的摄食等级、肝重指数和繁殖特征上两洋区无显著性差异(P0.05)。

Comparison of biological characteristics of Pseudocarcharias kamoharai between the tropical Atlantic and the tropical Pacific

Crocodile shark,Pseudocarcharias kamoharai,is a common by-catch species in tuna longline fishery.This species plays a very important role in the stability and diversity of the marine ecosystem.Though they are mostly situated at the topmost part of the marine ecosystem,they are always discarded due to their low commercial value.In order to provide references for the further biological studies of crocodile shark,the difference of population in the two ocean areas,evaluating and maintaining the Crocodile shark resources,a total of 1 426 ind crocodile shark was recorded according to the biological data collected by Chinese longline fishery observers in the tropical Atlantic from 2011 to 2015(6.38°S-14.92°N,42.03°-18.53°W) and a total of 1 037 ind crocodile shark was recorded according to the biological data collected in the tropical Pacific from 2006 to 2015 (16.88°S-10.85°N,163.13°E-177.75°W).The biological characteristics of crocodile sharks in these two oceans were analyzed and described by gender,respectively.The results were summarized as follows:(1) There were significant differences in the average fork length,dominant fork length and the relationships of fork length and body weight between the male and female P.Kamoharai by KolmogorovSmirnov test.The average fork length and dominant fork length of P.Kamoharai in the tropical Pacific were larger than those of the tropical Atlantic by T-test;(2) There were significant differences in the relationships of fork length and round weight between male and female P.Kamoharai by covariate ANOVA test;(3) The female-male ratio were 1∶0.80 and 1∶1.71 in the tropical Pacific and tropical Atlantic,respectively,with significant differences by Chi square test;(4) There was no significant difference in the relationships of feeding levels,Hepatosomatic Indices (HSI) and biology of reproduction between P.Kamoharai in the tropical Pacific and tropical Atlantic.The feeding level of P.Kamoharai in the two ocean areas was mainly 0 and Ⅰ.Atlantic and Pacific feeding levels were 64.5％,75.2％ for the females and 78.3％,87.8％ for the males,respectively.Female' s HIS was 18.33 ± 5.0,18.58 ± 5.3,and male was 18.33 ± 5.0,18.58 ± 5.3 in two oceans,respectively.The pups of P.Kamoharai at one birth were in the range of 1-6 ind,and 4 at one birth accounted for 81％ and the female-male ratio of pups was 1∶1 in both ocean areas.The results showed that there were significant differences in body size and sex ratio between P.Kamoharai in the tropical Atlantic and tropical Pacific but cannot conclude that they belong to different subspecies.