渤海鱼类群落功能群及其主要种类

根据2009年8月和10月对渤海渔业资源的底拖网调查,采用胃含物分析、聚类分析和功能群划分的方法研究了渤海鱼类群落的功能群组成及其主要种类。结果表明,渤海夏、秋季鱼类群落包括7个功能群,分别为浮游动物食性功能群、杂食性功能群、底栖动物食性功能群、虾食性功能群、虾/鱼食性功能群、鱼食性功能群和广食性功能群;其中主要功能群为浮游动物食性功能群、杂食性功能群和虾/鱼食性功能群;主要种类有小黄鱼、蓝点马鲛、斑、赤鼻棱鳀、银鲳和黄鲫。圆筛藻、中华哲水蚤、太平洋磷虾、长额刺糠虾、中国毛虾、甲壳类幼体、日本鼓虾、六丝矛尾虎鱼、小黄鱼、双壳类和腹足类是当前渤海夏、秋季鱼类群落的主要饵料种类。

Functional groups of fish assemblages and their major species in the Bohai Sea

The Bohai Sea is a semi-enclosed shallow sea and is an important spawning,nursery and feeding ground for many migratory species from the Yellow Sea.Currently,overfishing and environment degradation may have changed the community structure in the Bohai Sea.The decline in the biomass,species composition,and size spectrum indicates a degradation of the Bohai Sea ecosystem.At the same time,the mean trophic level at high trophic level declined faster than global trend.So,it is very necessary to re-understand the feeding relationship in the Bohai Sea.Based on the data collected from bottom trawl surveys conducted in August and October of 2009 in the Bohai Sea,23 kinds of fish species,not including silver pomfret Pampus argenteus,and 7263 stomach samples were analyed.According to stomach analysis,the cluster analysis,of which 60% of similarity level was used as criterion,was used to study the functional groups and their major species of fish assemblages in the Bohai Sea.The results suggested that seven functional groups were divided among fish assemblages in the Bohai Sea,that is zooplantivores,omnivores,benthivores,shrimp predators,shrimp/fish predators,piscivores and generalist predators.In China coastal seas,the trophic structure of the Yellow Sea and Bohai Sea was similar and they belong to a large marine ecosystems,so variations in their fisheries resources relate closely with each other.Although according to the biomass,zooplantivores,omnivores and shrimp/fish predators were all major functional groups in August and October,there were some remarkable seasonal differences between two months.There were seven functional groups in August and six functional groups in October.The most important is that the proportion of each functional group was different.In August,zooplanktivores functional group accounted for larger proportion,but coming into October,the proportion of zooplanktivores functional group substantially declined,and the proportion of omnivores,piscivores and generalist predators functional groups increased.Fish assemblages at different ontogenetic phases was the major reason causing those differences.Since most marine species in the Bohai Sea are migratory species,which come into the Bohai Sea in spring and leave in late autumn,the further study on the difference of functional groups should take into account seasonal migration of fish assemblages.The results also showed that there were 5 major species:small yellow croaker Pseudosciaena polyactis,Spanish mackerel Scomberomorus niphonius,gizzard-shad Clupanodon punctatus,silver pomfret and half-fin anchovy Setipinna taty in August,small yellow croaker,rednose anchovy Thrissa kammalensis,silver pomfret,gizzard-shad and half-fin anchovy in October,respectively.According to their diet composition,Coscinodiscus sp.,Calanus sinicus,Euphausia pacifica,Acanthomysis longirostris,Acetes chinensis,Maeruran larva,Alpheus japonicus,Chaeturichthys hexanema,small yellow croaker,gastropoda and bivalvia were main prey species in the Bohai Sea,but now,anchovy and crab are not the main prey species.