冬季东海外海鱼类群落特征及其对拉尼娜事件的响应

根据2004年12月和2008年12月东海区渔业资源底拖网调查资料,利用多元分析非度量多变量排序(nMDS)、SIMPER],对比分析正常年份(2004年)和拉尼娜(La Ni(n)a)年份(2008年)不同生态属性鱼类的变化特征,探究鱼类群落结构对拉尼娜事件的响应模式.结果表明,2008年冬季与2004年冬季相比,调查水域的种类组成由45种增加至61种,其中,暖水性种类比例减少,暖温性种类比例增加.主要优势种年间变化不大,仍为带鱼(Trichiurus japonicus)和小黄鱼(Larimichthys polyactis),两者资源密度之和分别占总资源密度的59.95％和55.16％.不同生态属性种类的资源密度发生了显著变化,以带鱼(Trichiurus japonicus)为代表的暖水性鱼类资源密度下降,而以小黄鱼(Larimichthys polyactis)为代表的暖温性鱼类资源密度增加.研究水域生物丰富度指数(R)、多样性指数(H')和均匀度指数(J))的均值均有所升高,但独立样本t检验表明,年间3指数间无显著性差异(P＞0.05).在捕捞压力保持相对稳定的情况下,群落组成的变化可能与拉尼娜事件有关,未来需要掌握不同种类对拉尼娜事件的响应模式.

Effects of La Niña on fish community structure in the offshore area of the northern East China Sea in winter

  A La Niña event is one of the strong signals of global climate anomalies. Understanding the consequences of La Niña event to marine ecosystems is important for improving fisheries stock assessment in the East China Sea. We compared species composition and the species diversity in winter between a normal year (2004) and a La Niña year (2008) in an offshore area of the East China Sea in winter using data collected from fisheries-independent bottom trawl survey. The number of observed species increased from 45 to 61 after the occurrence of La Niña. The number of warm water species decreased whereas warm temperature species increased. Though the dominant species composition only varied slightly, the stock density per station changed significantly. The stock density per station of warm water species such as Trichiurus japonicus decreased significantly whereas the stock density of warm temperature species such as Larimichthys polyactis tended to increase. Between the December of 2004 and 2008, the species richness indexes (R) increased from 1.56 to 1.92, the Shannon-Wienner diversity indexes (H′) increased from 1.23 to 1.42, and the Peilou evenness indexes(J′) increased from 0.51 to 0.57. There were no significant differences between the diversity indices accross the whole study area between 2004 and 2008. If the study area was divided into two parts, there was significant difference in the diversity indices between a normal year and a La Niña year in the southern region but not the northern region. The fishing pressure remained relatively stable during this period so the variability in fish community structure can likely be attributed to the change in climate in the East China Sea. The pattern and mechanism of the eco-response to the occurrence of La Niña events varies with the domain. Interdisciplinary studies are needed to improve our understanding of such events in the ecosystem.