气候环境因子和捕捞压力对南海北部带鱼渔获量变动的影响

Abstract

带鱼(<em>Trichiurus japonicas</em>)是南海北部的重要经济鱼类,其渔获量的变化不仅与捕捞压力有关,还与气候环境变化有关。为了研究气候变化和捕捞对南海北部带鱼渔获量变动的影响,使用长时间序列渔业统计资料和气候变化数据对1956-2006年的南海北部带鱼渔获量变动进行了分析。南海北部的带鱼渔获量变化可划分成因捕捞效应所产生的趋势变化和因气候环境变化所导致的渔获量变动。捕捞效应所产生的趋势变化可用Fox模型拟合,Fox模型拟合结果显示南海北部带鱼渔获量与捕捞努力量关系显著(<em>P</em><0.01),说明捕捞压力的增长显著影响到南海北部带鱼渔获量的变化。移除捕捞效应所产生的趋势变化后,渔获量变动与中国南方降雨、南海北部海表水温、南海北部夏季季风以及南海北部冬季季风等气候因子呈显著正偏相关(<em>P</em><0.04),与热带气旋影响指数呈显著负偏相关(<em>P</em><0.03),这种相关说明南海北部带鱼渔获量变动还受气候环境因子的影响。南海北部带鱼渔获量可用捕捞努力量和气候变量来拟合,且拟合效果显著(<em>R</em>²=0.958,<em>P</em><0.01),表明南海北部带鱼渔获量的变动归因于捕捞压力的单调增长和气候环境的变化。在南海北部的捕捞压力维持在现有水平下,未来的气候变化和人类活动引起营养盐的增加都可能有利于南海北部带鱼渔业产量的增加,且由于未来极端天气事件的频繁发生,可能还会引起带鱼渔获量的变动幅度加剧。;Hairtail (<em>Trichiurus japonicas</em>) is one of the most important kinds of commercial fishes in the northern South China Sea (NSCS). Changes to hairtail catches are not only related to fishing pressure but also to changes in the climatic environment. To understand the influence of climatic environmental factors and fishing pressure on the changes of hairtail catches in the NSCS, we have used long-term fisheries statistical data and climate change data to analyze the changes of hairtail catches between 1956 and 2006 in the NSCS. Hairtail catches in the NSCS can be divided into two parts: the trend of catches caused by fishing pressure and the alteration of catches influenced by climate change. Fitting the trend of catches to the Fox model shows significant relationships between fishing effort and hairtail catches in the NSCS (<em>P</em><0.01), which in turn demonstrates that growing fishing pressure has significantly affected the changes of hairtail catches in the NSCS. Before 1986, the growth of fishing effort was slow in the NSCS, and correspondingly, the growth rates of hairtail catches increased by a small margin. However, after 1986, with the rapid growth of fishing efforts and improved techniques for fishing, hairtail catches in the NSCS grew continuously and rapidly. After removing the effect of fishing pressure on the changing trends, we found that the alteration of catches had a significant positive partial correlation with precipitation in the southern China, as well as sea surface temperature, summer wind speed and winter wind speed in the NSCS (<em>P</em><0.04). Alteration of catches also had a significant negative partial correlation with the index of tropical cyclone influences (<em>P</em><0.03). This correlation showed that the alteration of hairtail catches was also affected by climatic and environmental factors. Rainfall runoff inputs a vast amount of nutrients into the estuary and adjacent waters. However, the monsoon-driven confluence and mixing between coastal and surface waters, as well as vertical mixing between the upper and lower waters, diffuses the distribution of nutrients in the NSCS, aides the efficient use of nutrients, and is conducive to the growth of phytoplankton in the sea. In addition, changes in ocean temperatures directly or indirectly had an effect on the various life stages of marine fish, particularly on the metabolism of fish and the rate of the reproductive cycle. Finally, the tropical cyclone changed the living environment of the hairtail, which would in turn affect its concentration, feeding and migration. Hairtail catches in the NSCS can be highly significantly fitted to fishing efforts and climatic variables (<em>R</em>²=0.958,<em>P</em><0.01). That is to say, changes of hairtail catches in the NSCS can be confidently attributed to a monotonic growth in fishing pressure and changes of the climatic environment. If the fishing pressure stays unchanged, the future climate changes and human activities that cause the increase of nutrients in the seas are likely to result in an increase in hairtail catches in the NSCS. Moreover, the increased frequency in extreme weather events that is predicted in the future may also cause larger fluctuations of hairtail catches.