Community Structure And General Situation Of Fishery Resources In Coastal Waters Of Southern Zhejiang

This article is based on the fall of 2015(November),and in the winter of 2016(February),spring(may)and summer(August)in southern zhejiang coastal waters bottom trawl surveys,the use of dominant species and richness,diversity and evenness index in southern zhejiang coastal Marine fishery resources community composition,seasonal change and biodiversity,The resources of swimming animals in the coastal waters of southern Zhejiang were estimated by using the methods of fishing effort per unit and scavenging area.Taking hairtail as an example,the resources of main economic fish were evaluated.The results are as follows:(1)A total of 290 species of swimming organisms(fish and macroinvertebrates)were collected in the offshore waters of southern Zhejiang,belonging to 5 phyla,10classes,40 orders,124 families and 201 genera.The number of fish species in spring voyage in 2016 was the largest,followed by autumn voyage in 2015,winter voyage in2016,and summer voyage in 2016 was the least.The four seasons of crustacean species richness from high to low were winter,autumn,spring and summer.The pattern of mollusk species is similar to that of crustaceans,while echinodermata and cnidaria species are 1-3 in each season.From the perspective of classification diversity,there is no significant difference in the number of programs and divisions among the four seasons,but the number of autumn voyages is significantly higher than that of other seasons.Dominant species in autumn and winter,spring and summer respectively:11,eight,nine and ten kinds,seven stars bottom lamp fish and leading to southern zhejiang coastal dominant species throughout the year,hairtail in addition to the winter,all other quarters as the dominant species,small yellow croaker in winter and summer has greater advantage position,and other types of seasonal dominant species,the dominant position appear only a voyage.In terms of species number,the average number of species at each station in autumn and winter was the same(51 species for both),followed by 47species in spring,and only 35 species in summer.In terms of species richness,winter was the highest and summer was the smallest.Comparing the values of the overall diversity level,it was found that winter was the highest,followed by autumn,spring,and summer was the lowest,which showed the same change trend as the richness index.(2)The existing resources of swimming animals in the offshore waters of southern Zhejiang are 41346.45t,and the existing resources of fish are 37088.60t and crustaceans3132.31t in total(803.16t for shrimp,1482.85t for crab and 846.30t for mantis shrimp).The existing resource of cephalopod is 998.26t.According to the estimation based on the sea-sweeping area method,the average stock of fishery resources in the coastal waters of southern Zhejiang in four seasons is 15100t,with a 95%confidence interval of 8300t-22000t.Among them,the largest stock of fishery resources is in summer(33800t),2.82 times of that in spring,3.37 times of that in autumn and 7.28 times of that in winter.The CPUE of fish ranked first,with an average annual CPUE of 1105.85kg/h·km~2.The second was crustaceans(including shrimp,crab and mantis shrimps),with an average CPUE of 98.31 kg/h·km~2.The CPUE of cephalopods was in the last position,and the annual average CPUE value was only 24.17 kg/h·km~2.(3)A total of 398 females were captured in four voyages in the coastal waters of southern Zhejiang province.The anal length ranged from 8.4 cm to 28.9cm,with an average of 17.47cm.The anal length of 349 males ranged from 8.0 to 28.6cm,with an average of 15.98cm.The regression relationship between anal length and body weight was a power function:W=0.0212l2.8029(R2=0.9199),parameter B≈3,indicating that the growth rate of hairtail was uniform.The anal length of female and male at first sexual maturity was 23.37cm and 21.25cm respectively.Using Pauly empirical formula for scientific calculation,we can get the natural death coefficient M=1.95,fishing death coefficient F=3.81,development rate E=0.66,current fishing state Y′/R=0.032(M/K=1.30,Lc/L∞=0.34,E=0.66),The fishery resources of hairtail are difficult to achieve sustainable and healthy development.