热带大西洋拟锥齿鲨资源动态和空间分布研究

Preliminary analysis of crocodile shark (Pseudocarcharias kamoharai) resources information and spatial distribution in the tropical Atlantic Ocean

摘要:

拟锥齿鲨是热带大西洋金枪鱼延绳钓渔业中较为常见的兼捕物种，处于海洋生态系统的顶端，对维持海洋生态系统的稳定性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2010—2015年在热带大西洋海域调查时收集的1 561尾拟锥齿鲨数据，对其资源动态和空间分布进行了初步分析，结果表明：在研究的海域内（6.33°S～17.43°N，18.25°W～42.03°W），拟锥齿鲨CPUE高的区域为5°N～10°N，20°W～30°W；2010—2015年CPUE呈现波动，整体有上升的趋势，但不显著；软骨鱼类占总渔获物的比例整体呈下降趋势；拟锥齿鲨兼捕数量占总渔获的5.8%，占兼捕软骨鱼类的22.5%；拟锥齿鲨在12 月—3月的平均CPUE较高。拟锥齿鲨最大叉长组（叉长范围在85～90 cm）的个体多分布在5°N～7.5°N，27.5°W～37.5°W和5°N～0°，25°W～30°W这两个区域。拟锥齿鲨理论钩获深度范围为140～313 m，平均深度为221 m。1、2、3钩位（140～212 m）的上钩频率最大，占总上钩率的55.59%。10月至次年4月不同月份拟锥齿鲨的钩位分布没有显著性的差异。妊娠期拟锥齿鲨明显分布于较浅的水层。不同钩位拟锥齿鲨的摄食等级无显著性差异。

Abstract:

Crocodile shark (Pseudocarcharias kamoharai) is a common bycatch species in tropical Atlantic tuna longline fishery. This species is mostly distributed at the topmost parts of the marine ecosystem and plays a very important role in the stability and diversity of the marine ecosystem. A total of 1 561 ind. crocodile sharks were recorded according to the biological data collected by Chinese longline fishery observers in the tropical Atlantic Ocean from 2010 to 2015 and the preliminary analyses about its resource information and spatial distribution were made. The results were summarized as follows: In the study area (6.33°S-17.43°N,18.25°W-42.03°W), the highest concentration of the CPUE area was in the zone 5°N-10°N, 20°W-30°W; the CPUE value was in the range: 0.00-3.94, and the average was 0.83. From 2010 to 2015, CPUE showed a variation trend, but the upward trend was not significant. The Chondrichthyes percentage in total proportion of the catch decreased; the total number of crocodile sharks accounted for 5.8% of total number of fish caught, accounting for 22.5% of the total number of Chondrichthyes bycatch. The higher average CPUE values of the tropical Atlantic crocodile sharks were recorded in December, and from January to March. The largest fork length class (fork length range of 85-90 cm) of the crocodile sharks were distributed in the regions 5°N-7.5°N, 27.5°W-37.5°W and 5°N-0°,25°W-30°W.Crocodile shark hook depth ranges between 140-313 m, the average observed depth was 221 m.The frequency of 1-3 hooks (140-212 m) is the largest, accounting for 55.59% of the total catch rate. There was no significant difference in the hook position of the crocodile shark in different months from October to April. Crocodile sharks were obviously distributed in the shallow water layer during pregnancy. There was no significant difference between feeding level and hook position of crocodile sharks.