渤海湾鱼类早期资源群落结构特征及其时间变化研究

Temporal variation of the early life stages of marine fish assemblage structure and abundance in the Bohai Bay

关键词:  鱼类早期资源  补充量  产卵育幼场  物种多样性  长期变化  渤海湾

Key words:  Early life stages of marine fish  Recruitment abundance  Spawning and nursery habitat  Species diversity  Long-term variation  Bohai Bay

摘要:

渤海湾历史上为黄渤海多种主要经济鱼类的重要产卵和育幼场。基于历史调查资料和补充调查，构建渤海湾鱼卵、仔稚鱼调查数据集，通过数理统计分析阐述1982年以来渤海湾鱼类早期资源(浮性鱼卵和仔稚鱼)群聚特性和演替过程。结果显示，渤海湾鱼类早期资源结构、产卵和育幼场重心位置处于持续更替过程中，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，118º30ʹE以西湾中底部海域一直为产卵和育幼场集中分布区。相较1980s，渤海湾鱼类早期资源已发生结构性改变，且渤海湾作为传统经济鱼类的产卵和育幼场所的功能下降明显。渤海湾鱼类早期资源种数和资源丰度均在2010s前期跌至历史低值，近年来又显著回升。鱼类早期资源种数由1980s的39种，1990s前期的31种、后期的34种，2000s—2010s初期的22 种，逐次下降至2010s前期的21种，2010s中后期开始逐步回升，至2020s初期已达40种。2020—2021 年鱼卵种数约为1980s的80%左右，资源丰度约为彼时的88%；仔稚鱼种数与1980s大致相当，资源丰度则为彼时的1.33倍。鱼卵、仔稚鱼物种多样性水平呈年际和年代际剧烈波动，鱼类早期资源种类年际更替现象明显，且近年来呈明显加快趋势。产卵类型、栖息类型和适温类型亲体种数均呈先下降后上升的变动趋势，全年综合浮性卵种数比例下降，黏性卵和具卵膜丝卵种数比例升高；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降低。斑 (Konosirus punctatus)、青鳞小沙丁鱼(Sardinella zunasi)、小黄鱼(Larimichthys polyactis)、带鱼(Trichiurus japonicus)、花鲈(Lateolabrax maculatus)和半滑舌鳎(Cynoglossus semilaevis)等渤海湾传统经济鱼类早期资源密度显著降低；鳀(Engraulis japonicus)、蓝点马鲛(Scomberomorus niphonius)、赤鼻棱鳀(Thryssa kammalensis)和少鳞 (Sillago japonica)等鱼类早期资源密度显著增高。渤海湾鱼类早期资源发生量主要取决于产卵场的环境条件、捕捞强度和对鱼类早期资源的损害程度，渤海湾鱼类早期资源结构及其动态变化是环境和捕捞双重扰动下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。

Abstract:

Bohai Bay is an important spawning and nursery habitat for a variety of economically important fish inhabiting the Yellow and Bohai seas. Based on a meta-analysis of historical data spanning 40 years, combined with a field survey of current fish habitat conditions conducted in Bohai Bay, a long-term dataset containing early life resource surveys (including 53 voyages, from 1982 to 2021) of marine Osteichthyes was built. Based on statistical analyses, long-term trends in ichthyoplankton assemblage structure, biodiversity, and synchrony were interpreted. The results indicate that ichthyoplankton assemblage structure and the center of gravity for spawning and nursery habitats in Bohai Bay are currently experiencing continuous replacement. Seasonal variations in ichthyoplankton assemblage structure, abundance index, predominant taxa, and species diversity levels are evident. Spawning and nursery habitats are concentrated in the central and inner part of Bohai Bay west of 118º30'E. Compared with survey results from the 1980s, the taxonomic composition and abundance of the ichthyoplankton assemblage structure have changed considerably. The function of Bohai Bay as a spawning and nursery habitat for traditionally economically important fish has declined significantly. The abundance index and taxon number of ichthyoplankton in Bohai Bay fell to a historic low in the early 2010s, then rebounded significantly. The taxa number of ichthyoplankton decreased from 39 in the 1980s to 31 in the early 1990s, 34 in the late 1990s, and 22 in the 2000s to pre-2010s, then further decreased to 21 in the early 2010s. From the middle 2010s, it recovered to a certain degree, increasing to 40 species just prior to 2020. The current number of pelagic egg taxa is 22, 80% of the number in the 1980s, and 88% of the abundance in the 1980s. The current (2020—2021) number of larval fish taxa is 26, almost identical to that in the 1980s, with an abundance 1.33 times greater than that in the 1980s. Interannual and interdecadal variations in fish egg and larvae species diversity fluctuated drastically. Interannual taxon substitution was noticeable. However, the substitution rate has increased significantly in recent years. Spawning, habitat, and temperature adaptation studies of breeding stock indicate that the number of taxa first decreased, then increased. The annual proportion of the number of taxa to pelagic eggs decreased, while the proportion of the number of taxa to adhesive eggs and eggs with egg membrane filaments increased. The annual proportion of continental shelf pelagic-neritic fish taxa increased, while the continental shelf demersal and benthopelagic taxa decreased. The ecological density of numbers in the early life history (EDN-ELH) of Konosirus punctatus, Sardinella zunasi, Larimichthys polyactis, Trichiurus japonicus, Lateolabrax maculatus, and Cynoglossus semilaevis decreased significantly, whereas the EDN-ELH of Engraulis japonicus, Scomberomorus niphonius, Thryssa kammalensis, and Sillago japonica increased. Ichthyoplankton abundance in Bohai Bay mainly depends on environmental conditions in the spawning habitat, fishing intensity, and the degree of damage to the early life stages of fish resources. The temporal variation and succession of the ichthyoplankton assemblage structure in Bohai Bay were the specific manifestations of the multidimensional niche disturbance and structural performance deterioration of the fishery resources under the dual disturbance of global warming and overfishing.