哥斯达黎加海域茎柔鱼角质颚稳定同位素研究

Stable isotope of beak for Dosidicus gigas off Costa Rica coast

头足类的角质颚具有结构单一和不易腐蚀的特性，其稳定同位素分析已成为头足类生态学研究的主要方法之一。根据2009年7-8月我国鱿钓船在哥斯达黎加外海捕捞的茎柔鱼样本，对其角质颚进行稳定同位素分析，探讨其与胴长、日龄、性腺成熟度等之间的关系。结果表明，茎柔鱼样本的胴长范围在25.6～35.8 cm之间，体重范围在447.6～1 122.3 g之间，为小型群体；上、下角质颚的δ13C和δ15 N有所差别，但无显著性差异（P〉0.05）；δ13C和δ15N值随着胴长和日龄的增大而增大，两者均符合线性关系；不同性成熟度的个体也有着不同的δ13C和δ15 N值，其中性成熟度为Ⅲ期个体的值最大。δ13C和δ15N值反应出茎柔鱼在生长过程中，其栖息环境从大陆架向大洋转变，活动范围也向着生产力更高的海域聚集，同时与性成熟和个体生长过程密切相关。建议今后应结合研究海域的浮游生物，对角质颚等不同硬组织及其不同部位稳定同位素进行深入分析，以便为了解和掌握茎柔鱼的生态学提供理论参考。

Stable isotope in the beaks has become a good material for ecological study of cephalopod as the characteristic of single structure and incorrosiveness. In this study, the stable isotopes of beak and its relationship between mantle length, age and sexual maturity were analyzed based on the samples of Dosidicus gigas collected by Chinese jigging vessel during July to August in 2009. The results showed that the mantle length of samples ranged from 25.6 to 35.8 cm, body weight ranged from 447.6 to 1 122.3 g,and these samples belonged to small group. The values of δ13C and δ15N of lower beaks was higher than upper beak, but the difference was not significant （P〉0.05）. The values of δ13C and δ15N increased by mantle length and age, their relationships were fitted by the linear model. The values of δ13C and δ15 N were variable with different sexual maturity stage, and the sample with stage Ⅲ has the maximum value of δ13C and δ15 N. The results indicated that its habitat shifted from the continental shelf to the ocean and the scope of activities of Dosidicus gigas gathered toward more productive waters from the changes of δ13C and δ15N during the growth process of Dosidicus gigas. At the same time, the changes of δ13C and δ15 N were closely related with sexual maturity and individual growth process. It is recommended that the stable isotope of the beak and other hard tissues and its different parts should be studied combined with marine plankton in the studying area in order to provide a basis to understand and master the ecology of Dosidicus gigas in the future.