南海北部中华哲水蚤的繁殖和种群补充机制

Calanus sinicus is a planktonic copepod that is widely distributed in the continental shelf of the northwest Pacific from the Japan Sea to the Vietnam coastal waters of South China Sea.This species dominates the mesozooplankton community with its characteristic large size and wide distribution.The adults, larvae and eggs are an important food source for many fish stocks. Because of its important role in the marine ecosystem, C. sinicus is a target species of the China-GLOBEC research program. Since the 1960s, Chinese scholars have accumulated rich biological and ecological information on C. sinicus in the Bohai Sea, Yellow Sea and the East China Sea. However, data on its emergence, distribution, as well as the recruitment process and mechanism are poorly understood in the South China Sea at present. To test these ideas, we aim to find out the population structure, abundance and spatial and seasonal changes in reproductive process of C. sinicus in the northern part of South China Sea, and to reveal the essential physical and biological processes influencing on their population dynamics. The results will improve our understanding on some scientific questions about C. sinicus in China's offshore waters, such as their population emergence, recruitment and mechanism of their distribution, and their life history strategy etc., which is of the greatest theoretical and realistic significance for our country's sustainable utilization of marine biology resources, the structure fishery resources and response to climate change.

中华哲水蚤，作为我国近海浮游桡足类的优势种，是我国近海生态系统结构和功能研究的关键种。20世纪60年代至今，我国学者在渤海、黄海和东海的中华哲水蚤生物学和生态学研究方面积累了丰富资料，而对南海中华哲水蚤的种群发生、发展以及补充过程和机制知之甚少。本项目通过对南海北部中华哲水蚤的调查和实验，阐明南海北部中华哲水蚤种群结构、丰度以及繁殖过程的区域和季节变化，揭示南海北部中华哲水蚤种群补充的过程，探讨环境因子对南海北部中华哲水蚤繁殖和种群补充的影响。研究结果将提升对中国近海中华哲水蚤的种群发生、增长和生活史策略等关键科学问题的认识，为我国海洋生物资源可持续开发和利用以及近海生态系统对气候变化的生物响应等提供科学依据。

中华哲水蚤是我国近海生态系统结构和功能研究的关键种，在渤海、黄海和东海对该种进行了较多研究，至今对其在南海的相关研究资料较少。因此本课题对中华哲水蚤在南海的种群发生、发展以及补充过程和机制进行了分析和探讨。以大亚湾为重点海域，主要开展了以下四个方面的研究内容。（1）南海北部乃至西太平洋沿岸海域中华哲水蚤的季节出现规律：中华哲水蚤在大亚湾1—5月份出现，6月份开始消失；从西太平洋沿岸38ºN至22ºN中华哲水蚤从周年出现逐渐变化到仅冬、春季出现。（2）南海北部中华哲水蚤丰度的分布和变化：大亚湾中华哲水蚤丰度有明显的季节和空间变化，高丰度主要出现在1-2月份。1月中华哲水蚤只要出现在西南部，2月份扩展到整个海湾，3月份呈斑块分布，4月份退至湾口。（3）南海北部中华哲水蚤的种群结构和繁殖率：桡足幼体II-V期和成体在505um采样样品中占优势，而无节幼体III-V期、桡足幼体I-V期和成体在160um采样样品中占优势。成体在1月份丰度最高，然后逐渐减少。在505um样品中最高繁殖率在2月份，小于3；而在160um样品中最高繁殖率在4月份，接近6。（4）南海北部中华哲水蚤分布的影响因素和补充机制：种群输送和水温是决定南海北部中华哲水蚤出现和生存的首要环境因素。中华哲水蚤在夏季底层温度较低时仍然存在一定的数量，与夏季沿岸上升流的强度有关。南海北部中华哲水蚤的度夏与夏季黄海冷水团该种的度夏机制相似。以上研究结果基本回答了影响南海北部中华哲水蚤种群补充过程的环境因素和夏季沿岸上升流能否为其提供度夏场所的科学问题，为我国海洋生物资源可持续开发和利用以及近海生态系统对气候变化的生物响应提供科学依据。