近30年渤海鱼类种群早期补充群体群聚特性和结构更替

基于30余年渤海鱼卵、仔稚鱼历史调查资料的整理分析并结合产卵场补充调查,以1982~1983年周年逐月调查资料为本底,采用多元统计学方法分析30余年渤海鱼类种群早期补充群体群聚特性(物种多样性和关键种群)的季节变化和年代际变化,并掌握结构更替过程中优势种和重要种协同消长规律。分析结果显示,渤海各调查季节(冬季除外)鱼卵、仔稚鱼种类数以及资源丰度指数呈先降后升变动趋势。当前鱼卵种类数仅为20世纪80年代1/2左右,资源丰度不足20世纪80年代的1/10;仔稚鱼种类数和资源丰度仅为20世纪80年代的3/4左右,但冬季仔稚鱼种类数和资源丰度指数呈现上升趋势。各调查时期相同季节鱼卵优势种变化不明显,但仔稚鱼优势种变化幅度超过鱼卵,底层重要经济种类早期补充群体优势度急剧下降;鱼卵和仔稚鱼物种多样性水平在升温季节较高而在降温季节较低,调查期内各季主要呈现先降后升变动趋势。鱼类早期补充群体种类更替现象明显,近年来种类更替率呈现明显加快趋势。各调查时期相同季节各适温类型产卵亲体种数均呈现先降后升变动趋势,但各适温类型种数所占比例和全年综合各适温类型种数所占比例基本稳定。各调查时期相同季节各主要栖所类型产卵亲体种类数也均呈现先降后升变动趋势,全年综合陆架浅水中上层鱼类种数所占比例升高,中底层和底层鱼类所占比例有所下降。近30年在多重外来干扰作用下,渤海鱼类早期补充过程各个关键环节已随其栖息地(产卵场)生境要素发生不可逆变化或变迁。渤海鱼类种群早期补充群体群聚特性和结构更替是环境-捕捞胁迫下鱼类群落内多重生态位的交替失调和渔业资源结构性衰退的具体表现。

Ichthyoplankton Succession and Assemblage Structure in the Bohai Sea During the Past 30 Years Since the 1980s

The ichthyoplankton assemblage structure and succession in the Bohai Sea were studied using multivariate statistical analysis of monthly investigation data collected from April 1982 to May 1983 as background. Based on a pooled analysis of the historical data of fish eggs and larvae sampled from the horizontal trawl surveys during oceanographical expedition cruises over the past 30 years combined with the field survey of current fish habitat conditions, this study aimed to investigate the seasonal and interdecadal variations in the species diversity and key species, and the changing collaboration between the dominant species and the important species in the succession process. Compared with the survey results of 1982~1983, the profiles of the species number and abundance index of fish eggs and larvae during the survey season across different survey times present different degrees of decline (except in winter), and display a tendency towards decline at the beginning and an increase later. The species number of the fish eggs was only one half in the 1980s, and its abundance index was only one tenth in the 1980s. The species number and abundance index of fish larvae were only three fourths in the 1980s, however, these have shown an obvious increasing tendency in the recent years during winter. During the investigation period, species substitution in the early life stages of fish was obvious, otherwise, the substitution rate was significantly accelerated in the recent years. The dominant species of fish eggs did not change significantly during the same season in each investigation period, however, variation in the dominant species in fish larvae was more obvious. The dominance of the continental shelf demersal fish communities with high commercial value decreased sharply, although some species disappeared in recent surveys. The biodiversity index of fish eggs and larvae was higher during the sea temperature rising season and lower during the sea temperature cooling season. The index profiles during the survey season across different survey times showed a tendency of decreasing first and then increasing. Temperature adaptation studies on the spawning stock profiles during the survey season across different survey times showed that species number in each temperature adaptation type showed a tendency of decreasing first and then increasing. Even so, the seasonal or annual percentage of each type remained stable. Habitat studies on the spawning stock showed that the species number of the main habitat type also rose after showing a declining trend first, and presented different degrees of decline. The annual percentage of the continental shelf pelagic-neritic fish increased, in conjunction with the continental shelf demersal and benthopelagic fish decrease. Under the multiple sources of exogenous interference factors, irreversible changes have been taking place in every key link of the recruitment process in the early life stages of the fish, with habitat loss or fragmentation in the Bohai Sea during the past 30 years. Stressors such as overfishing and climate change promote multidimensional niche disturbances in the fish community and structural decline in the fishery resources, while the succession and assemblage structure of the fish eggs and larvae are the embodiment of this development.