渤海莱州湾硬骨鱼类早期资源群落结构及演变

Early life resources assemblage structure and succession to the marine Osteichthyes in the Laizhou Bay of Bohai Sea

摘要:

莱州湾作为黄渤海众多渔业生物关键栖息地，其鱼类早期发生量和补充量直接影响渤海乃至黄海渔业资源动态及其可持续性。实验基于历史调查资料并结合补充调查，构建莱州湾鱼卵、仔鱼调查数据集，通过数理统计和时间序列分析阐述近40年来莱州湾鱼类早期资源(浮性鱼卵、仔稚鱼)群聚特性和演替过程。结果显示，莱州湾鱼类早期资源结构处在持续更替过程中，不同时期早期资源的种类组成、资源丰度、优势种类和物种多样性水平等呈明显季节更替。鱼卵和仔稚鱼种类数和资源丰度均在2010s (2010—2019，以下同此表示) 初期跌至历史低值，近年来均又呈现一定程度回升。鱼卵和仔稚鱼种类数由1980s的44种，1990s前期的34种、后期的40种，2000s的35种，逐次下降至2010s前期的24种，2010s中后期开始逐步回升至38种。当前鱼卵种数仅为1980s的60%左右，资源丰度不足彼时三分之一；仔稚鱼种数为1980s的四分之三左右，资源丰度约为彼时的90%。生命周期短、性成熟早、处于食物链低端的中上层和底层小型鱼类为莱州湾鱼类早期资源的主体成分。长期变化，相同季节优势种种类更替现象明显，且近年来呈明显加快趋势；鱼卵仔稚鱼物种多样性水平呈年际和年代际剧烈波动；栖息类型、适温类型产卵亲体种数均呈先降后升变动趋势，全年综合陆架浅水中上层鱼类所占比例升高，中底层和底层鱼类所占比例降低。研究表明，与20世纪80年代相比，莱州湾鱼类早期资源已发生结构性改变，这些变化均由一系列复杂并不断变化的环境条件与鱼类早期资源每个物种数量动态相互作用驱动，是捕捞和环境双重压力下导致鱼类群落内生态位错位交替和结构性渔业资源衰退的具体体现。

关键词:硬骨鱼类;鱼类早期资源;补充量;物种多样性;长期变化;时间序列分析;莱州湾

Abstract:

Habitats distributed in the Laizhou Bay were critical for the accomplishment of the life cycles of fish and productive fisheries, in the Bohai Sea or even in the Yellow Sea. Based on a pooled analysis of the historical data available for almost 40 years, and combined with the field survey of current fish habitat conditions, a long-term data set of early life resources surveys to marine Osteichthyes, carried out in the Laizhou Bay was built. Mathematical statistics and time series analysis were used to interpret the recruitment characteristics and long-term trends in early life resources assemblage structure, biodiversity, and synchrony. The analysis showed that the early life resources assemblage structure in the Laizhou Bay changed continuously. The seasonal differences in community composition, abundance index, predominant taxa, and species diversity to eggs and larvae fish assemblage were evident. The abundance index and taxa number of egg and larval fish assemblages declined to an all-time low around the early 2010s, after which it showed signs of recovery recently. The taxa number of egg and larval fish decreased from 44 in the 1980s, 34 in the early 1990s, 40 in the late 1990s, and 35 in the 2000s to 24 in the early 2010s; from the middle and late 2010s, it showed a certain degree of recovery, and recently increased to 38 species. The recent number of the pelagic eggs taxa is only sixty percent of that in the 1980s, and with its abundance less one-third of the 1980s. The number of the pelagic eggs taxa had fell to an all-time low around the early 2010s, with taxa number less than half of the 1980s; while, the abundance of the pelagic eggs fell to an all-time low around the late 2000s, with its abundance only one-twentieth of the 1980s. The number of larvae fish taxa decreased first and then increased in each season (except in winter), while the abundance of fish larvae first increased and then decreased, however, both showed an upward trend in winter. The recent number of the larvae fish taxa is only three-fourths of that in the 1980s, and with its abundance less than ninety percent of the 1980s. The number of the larvae fish taxa fell to an all-time low around the early 2010s, with the number of taxa only half of the 1980s; while, larvae fish abundance reached a historical peak around the late 2000s, with its abundance about 1.9 times as much in the 1980s. Small pelagic and benthopelagic taxa with short life span, rapid maturation, strong coupling to lower trophic levels, were the main components by relative abundance detected in the eggs and fish larvae collected across different survey periods. The dominant taxa substitution was obvious, otherwise, the substitution rate was significantly accelerated in recent years. A significant amount of interannual and decadal variability remained in the species biodiversity index during the same survey season. Habitat and temperature adaptation studies of the spawning stock showed that the number of taxa with different habitat types and different temperature adaptation types took on a tendency of first decreasing and then increasing, profiling in the survey seasons across different survey times; annual percentage of the continental shelf pelagic-neritic fish taxa increased, combined with the continental shelf demersal and benthopelagic taxa decreased. Compared with the survey result in the1980s, the taxonomic composition and abundance of the egg and larval fish assemblage changed considerably. These variations were determined by a complex array of continuously changing conditions interacting with the demographic variables of each species, which was the concrete embodiment of high turnover in fish community structure and decline of fishery resources under long-term effects of overfishing and environmental change. Systematically summarizing long term trends in early life resources assemblage structure, biodiversity, and synchrony in the Laizhou Bay, and looking at how communities have changed in the past can help us understand the mechanism of spawning habitats stability, which could provide scientific evidence on laying down certain measures for the conservation and management of fishery resources in the Laizhou Bay, and the following impact assessment. Such as fishing, pollution, mariculture, and large-scale coastal engineering projects on the relative effects of climate and anthropogenic-induced factors on marine fish populations.

Key words:Osteichthyes;early life resources;recruitment abundance;species diversity;long-term variation;time-series analyses;Laizhou Bay