ANALYSIS ON THE SPECIES DIVERSITY OF FISHERY ANIMALS IN DAIQUYANG

Abstract

The Daiquyang locates between the Daishan and Qushan Islands in the Zhoushan Archipelago.Due to its optimal location and suitable environmental characteristics,it is the spawning and feeding ground of Larimichthys crocea of the Daiqu Race,and also of other fishery animals(fish species such as Larimichthys polyactis,Trichiurus japonicus,Pampus argenteus and Engraulis japonicus,crustacean species such as Portunus trituberculatus,Charybdis japonica,Exopalaemon carinicauda,Acetes chinensis and Oratosquilla oratoria,cephalopods such as Sepiella maindroni,Octopus variabilis,Octopus ocellatus and Loligo duvaucelii,and other animal species such as Nassarius variciferus,Sliqua minima,Cantharus cecillei and Moerella irideseens).For a long time,although the Daiquyang plays an important role in marine fisheries in the East China Sea,there have been no studies focused on the species diversity of its fishery animals.In recent years,both the environment and fishery resources in the Daiquyang have been facing new threats arisen from rapid development of harbor industries and a mass of shore reclamation in the Zhoushan Archipelago District,Zhejiang.Therefore it is necessary to study the species diversity of fishery animals in this area.We analyzed fishery animal diversity and the status of fishery resources based on four surveys conducted by bottom trawl,setting gillnet and crab pot from April to November 2007 in the Daiquyang.Three analytical methods including sweep-area method,biodiversity analysis and analysis of variance were used.The results showed that: 1) a total of 98 fishery animals were sampled,including fishes(58 species),crustaceans(32 species),cephalopods(3 species) and other species(6 species),belonging to 53 families of 20 orders,7 classes and 4 phylums.2) In our trawl collections,a total of 68 fishery animals were obtained,including fishes(38 species),crustaceans(23 species),cephalopods(2 species) and other species(5 species),belonging to 42 families of 18 orders,7 classes and 4 phylums.The richness index(D) of fishery animals in April was significantly different from those in August and November(P 0.05).Both the biomass and the number abundance density indices of fishery animals were the highest in August,significantly different from those in May and November(P 0.05).The dominant species were Harpodon nehereus,Coilia mystus,Palaemon gravieri and Alpheus japonicus in April,Harpodon nehereus,Coilia mystus,Exopalaemon annandalei and Charybdis japonica in May,Harpodon nehereu and Portunus trituberculatus in August,Harpodon nehereus,Charybdis japonica and Oratosquilla oratoria in December,and among them,Harpodon nehereus was the dominant species during all study months.Average body weight of Harpodon nehereus in August was significantly different from those in other three months(P 0.05) because of the spawning of the juveniles.For trawl collections,the biological community was mainly composed of warm temperature fish species,eurythermal and euryhaline crustacean species(such as Harpodon nehereus,Coilia mystus,Alpheus japonicus,Portunus trituberculatus and Oratosquilla oratoria) with a small number of fishery animals and lower Shannon-Wiener diversity index(H′),compared with offshore waters and deep waters in the East China Sea,In addition,its biomass was closely related with the bottom water temperature(P 0.01).