长江口张网鱼类群落结构特征及月相变化

为了解长江口鱼类群落结构的现状及变化特征,用张网作业对长江口2010年5月至2011年4月12个月鱼类群落进行了调查。结果1周年共记录56种鱼类,以鲈形目(27种)和鲱形目(10种)种类数目最多。鱼类区系为典型的亚热带动物区系,只出现暖水种(25种)及暖温种(31种)2种适温类型。鱼类种类数目以底栖鱼类(26种)和中上层鱼类占多数(21种),底层鱼类数目较少(9种)。丰度或生物量均由少数几种鱼类占优势。根据鱼类生态类群,海洋洄游性鱼类及河口性鱼类占据种类数目的主要地位,而生物量或丰度均由海洋洄游性鱼类占据主导。每网平均种类数目的最大值和最小值分别出现在7月(18.3种)和1月(7.2种),每网丰度最大值和最小值出现在11月(2 272尾/网)和1月(71尾/网),生物量的最大值出现在9月(11 892g/网),最小值出现在1月(351g/网),而主要种类丰度的时间分布差异也较大;基于丰度计算的Shannon-Wiener多样性指数及Simpson优势度集中指数在时间上也有较大差异,NMDS非度量多维尺度分析显示根据相似性鱼类群落在时间上可分为4组,相邻月一般相似性较近,但2010年12月和2011年1月相似性较小。此外,多元回归分析表明,在径流量、盐度及水温3个环境因素中,引起张网鱼类群落丰度时间变化的主要影响因素是水温。鉴于当前长江口张网捕捞努力量有增加趋势,为保护长江口鱼类群落,需要控制过高的捕捞努力量。

Characteristic and monthly variations of set net fish community structure in the Changjinag River estuary

In order to analysis the current characteristics and temporal variations of fish community structure of the Changjiang River estuary, fishes were collected every month from May 2010 to April 2011, using set nets. During the study time, 56 fish species were sampled, Perciformes (27 taxa) and Clupeiformes (10 species) were the two most abundant orders. Among the total 56 species, 26 demersal species, 21 pelagic species and 9 benthic species were caught. Fish faunas showed typical subtropical features, thus 25 tropical species and 31 warm-water taxa were found respectively. Both abundances and biomass were dominated by a few species. In terms of fish ecological guild, numbers of species were mainly represented by marine migrants and estuarine species, while marine migrants were the most important guild whether in abundance or biomass. Mean fish species richness was lowest and highest recorded in January 2011 (7.2 species) and July (18.3 taxa), respectively. Total abundance had a minimum in January 2011 (71 individuals per net) and a maximum during November 2010 (2 272 individuals per net). Fish biomass, got reached minimum values in September (11 892 g per net), and maximum during January 2011 (351 g per net). Temporal variations in abundances of the most abundant species varied may be related to reduce the competition behaviour. Average Shannon-Wiener and Pielou indexes, using abundance data, reached maximum in July 2010 (2.69) and August (0.77), respectively, and both minimum June (1.44 and 0.44, respectively). Non-metric multidimensional scaling, NMDS showed that community structures in two continued months were similar, however, that in December 2010 differs from that in January 2011, the method also illustrated a clear division into four distinct groups of samples (GroupⅠ: samples capturing from January 2011 to April 2011; GroupⅡ: samples capturing from May 2010 to the first half month of August 2010; Group Ⅲ: samples capturing from the second half month of November 2010 to December 2010; Group Ⅳ: samples sampling between the second half month of August 2010 and the first half month of November 2010). Additionally, multi regression model demonstrated that among the three variables (temperature, salinity and inflow) examined, temperature was the most important variable influencing the abundance across the study period. Due to the increasing fishing pressure on fish community of the Yangtze River estuary, one measure for management is to reduce the high fishing effort.