中街山列岛海洋保护区鱼类物种多样性

基于2010-2012年在中街山列岛海洋保护区进行的8个航次底拖网调查数据资料,从鱼类分类学和生态类群等方面,结合多样性、资源密度和相对重要性指数,对该保护区鱼类物种多样性特征进行了分析。调查海域共采集鱼类55种,隶属2纲12目32科44属。其中,鲈形目鱼类26种,占47.3%;趋礁性鱼类41种,占74.5%;暖温性、暖水性和冷温性鱼类分别为30、24和1种,其中暖水种约占所有偶见种的70%;定居种、近海洄游种和季节性种分别为27、24和24种;底层、近底层和中上层鱼类分别占40.0%、36.4%和23.6%,其中矛尾鰕虎鱼(Chaeturichthys stigmatias)、龙头鱼(Harpodon nehereus)和鳀科鱼类分别成为各水层的绝对优势种。所有调查站点鱼类平均生物量指数夏季最高(1043.7 kg/km²),春季最低;尾数密度指数春季最高(122×10³ 尾/km²),冬季最低;生物量与尾数密度指数最高与最低季节之间均存在显著性差异(P<0.05)。对多样性的分析显示,Margalef丰富度(D)冬季最高,秋季最低,Shannon-Wiener多样性(H'')与Pielou均匀度(J'')均为夏季最高,秋季最低。聚类和NMDS方法分析显示不同季节鱼类群落组成格局差异极显著(P<0.01)。研究结果表明,中街山列岛海洋保护区鱼类资源结构受近海季节性洄游种类影响较大,鱼类分布季节动态多呈现洄游性更替节律,保护区内虽已出现鱼类多样性下降趋势和生态系统功能退化现象,传统经济种类的优越性在逐渐下降或边缘化,但独特的岛礁生境仍能很好地发挥着维持固有种类和提供良好栖息场所的优势,随着海洋牧场建设与一系列资源保护与修复措施,石首鱼科幼体已形成优势群体,而且保护区内出现大量小型饵料鱼类。

Fish species diversity in Zhongjieshan Islands Marine Protected Area (MPA)

The Zhongjieshan Islands Marine Protected Area (MPA) is located in the central area of the Zhoushan fishing ground. It lies to the east of Zhoushan Islands District in Zhejiang Province and is historically known as the "fish warehouse" of the East China Sea. Fish community taxonomy and eco-group data from eight bottom trawl surveys in Zhongjieshan Islands MPA, carried out from 2010 to 2012, were used to examine species composition in detail. Indices such as Margalef''s species richness index, Shannon-Wiener''s species diversity index, Pielou''s species evenness index, resource density index as well as Pinkas''s IRI were used to analyze the status of fish diversity in the protected area. A total of 55 fish species belonging to 2 classes, 12 orders, 32 families and 44 genera were collected during the survey. 26 species from the order Perciformes (accounting 47.3% of the total species) and 41 reef species (74.5% of the total species) were captured. There were 30 warm temperate species, 24 warm water species and 1 cold temperate species, and nearly 70% of total rare species were warm temperate species. There were 27 local species, 24 offshore migrating species and 24 seasonal species. Forty percent of the fish caught were demersal, 36.4% were meso-demersal and 23.6% were pelagic. The dominant species in each habitat layer was examined, Chaeturichthys stigmatias was the most abundant demersal fish, Harpodon nehereus was the most dominant meso-demersal fish. Fish in the family Engraulidae dominated the surface waters. The mean biomass index of the study area was highest in summer (1043.7 kg/km²) and lowest in spring. The abundance density index was highest in spring (122×10³ ind/km²), but lowest in winter. Both the biomass index and the abundance density index in the highest season were significantly different from that in the lowest season (P<0.05). The average Margalef''s species richness index was highest in winter, but lowest in autumn, while the highest and lowest of both Shannon-Wiener''s species diversity index and Pielou''s species evenness index were in summer and autumn, respectively. Hierarchical clustering and further non-metric multidimensional scaling (NMDS) analysis indicated extremely significant seasonal changes in the fish community structure (P<0.01). The structure of fish resources in Zhongjieshan Islands MPA was significantly influenced by offshore seasonal migrating species, and the seasonal dynamic of fish distributions showed alternate migratory rhythm. Although the diversity of the protected area showed a downward trend, and the dominance of traditional economic species gradually declined or marginalized, the unique reef habitat still played an important role in both maintaining the local species and offering more bio-available habitat. With the development of marine ranching and implementation of a range of resource protection and restoration measures, the family Sciaenidae became a dominant group, and a large number of small forage fish appeared in the protected area.