A Preliminary Study On Temporal And Apatial Changes Of Community Structure Of The Ichthyoplankton In Zhoushan Archipelago

Ichthyoplankton is a general term for fish eggs,larvae and juveniles.In order to know the community structure of the ichthyoplankton in Zhoushan Archipelago in spring and autumn,and the spatiotemporal changes of their resource quantities,4 horizontal trawling surveys about the ichthyoplankton were conducted in the Zhoushan Archipelago in April,November 2017 and 2018.Based on the analysis of the species composition,resource distribution,community structure distribution of ichthyoplankton and its relationship with environmental factors,the main conclusions are as follows:1.Through the combination of traditional morphology and DNA bar code technology,from 2017 to 2018,65 species of ichthyoplankton were collected in the sea area of Zhoushan Archipelago in spring and autumn,including 22 species of fish eggs and 56 species of larvae and juveniles,belonging to 13 orders and 35 families.The composition of dominant species of fish eggs has a seasonal unity,which in spring was Liza haematocheilus,in autumn was Harpadon nehereus.The composition of juveniles and juveniles has a seasonal change,which in spring was Acanthogobius ommaturus and Chaeturichthys stigmatias,in autumn was Salanx ariakensis.2.The biodiversity index showed that the abundance index(D)and diversity index(H)of fish eggs were higher in April than in November,and the diversity index of larvae and juveniles were the highest in November 2017.The seasonal variation trend of the ichthyoplankton resources is that the average abundance of fish eggs was the highest in November 2017,and that of larvae and juveniles was the highest in April 2017.The spatial distribution of fish eggs were mainly in the eastern waters of Zhoushan Archipelago,and the larvae and juveniles were mostly in the coastal waters and the western waters of Zhoushan Archipelago.3.The results of the CLUSTER analysis showed that the ichthyoplankton in Zhoushan Archipelago mainly distributed in four areas in spring:the shallow water area in the west of the island,the nearshore of the island,the deep water area in the north of the island and the deep water area in the southeast of the island.And the main divergent species are the Liza haematocheilus,Sebastiscus marmoratus and Acanthogobius ommaturus.Which were different in autumn:the shallow water area in the west and the north,near shore,he deep water area in the east.And the main divergent species were Harpadon nehereus、Larimichthys croceus and Salanx ariakensis.4.The results of redundancy analysis showed that the depth,temperature,salinity and dissolved oxygen had significant correlation with the distribution of fish eggs and larvae;in addition,the chlorophyll a content,water turbidity and other environmental factors which were affected by phytoplankton had significant correlation with the distribution of larvae and juveniles.5.Many important economic species were found in Zhoushan Archipelago,such as Larimichthys croceus、Larimichthys polyactis、Trichiurus lepturus、Pampus argenteus and so on,which showed that Zhoushan Archipelago is still an important spawning and fattening ground for fish,so we should strengthen the protection of Zhoushan Archipelago’s ecological environment.