Study On The Characteristics Of Structure Of Community Of Fishery Species In The Bohai Sea

The Bohai Sea is the spawning ground and feeding ground of important fishery economic species,and also one of the important fishing grounds of Marine fishery production in China.It occupies a vital position in Marine fishery in China.For decades,the fishery resources of Bohai sea are from the underfishing gradually deteriorated to overfishing and in great decline,and with the rapid development of economy of coastal provinces and cities,the ecological environment of the Bohai sea is getting worse and worse,which makes a great threat to the health Bohai sea ecosystem.Under the stress of fishing pressure and environmental change,the fishery community in the Bohai Sea is bound to have corresponding changes.Therefore,it is particularly important to study the characteristics of fishery community structure in the Bohai Sea,which can further promote the scientific management of fishery resources and the sustainable development of fishery resources.Based on the bottom trawl survey data of fishery resources in the Bohai Sea,this paper analyzed the characteristics of dominant species,catch per unit fishing effort(CPUE)and diversity in fishery biocumenies,and explored the seasonal changes of dominant species,relative abundance,relative biomass and economic value of fishery resources.The main research results are as follows:Based on the bottom trawl survey data of fishery resources in the Bohai Sea in August 2017,the characteristics of dominant species,catch per unit effort and diversity of fishery communities in the Bohai Sea were analyzed.The results showed that: in the summer of 2017,there were 73 species of fishery resources,including 44 species of fish,29 species of economically important invertebrates;The dominant species are Chaeturichthys stigmatias,Engraulis japonicus and Oratosquilla oratoria;The relative biomass of fishery species in the Bohai Sea is 87.62kg/h,including 55.27kg/h of fish,32.35kg/h of economically important invertebrates.The relative biomass of fishery species in the Laizhou Bay is 89.53kg/h,including 55.40kg/h for fish and 39.10kg/h for economically important invertebrates;The relative biomass of fishery species in the Liaodong Bay is 87.29kg/h,including 57.67kg/h for fish and 29.61kg/h for economically important invertebrates;The relative biomass of fishery species in the Central Bohai is 76.77kg/h,including 51.99kg/h for fish and 24.78kg/h for economically important invertebrates.Fishery species resources,fish resources and economically important invertebrates resources are all mainly distributed in the Laizhou Bay and the southwest of the Liaodong Bay.In the Bohai Sea,the Marglef index D is5.12,the Shannon Wiener index H′ is 1.79,the Pielou index J′ is 0.42.In the subareas of Bohai Sea,J′,H′ and the relative biomass in the Central Bohai Sea are significantly lower than those in the Liaodong Bay and the Laizhou Bay.There is little difference between the Laizhou Bay and the Liaodong Bay in terms of D,J′,H′,and the relative biomass of fish and economically important invertebrates.Based on the bottom trawl survey data of fishery resources in the Bohai Sea from May 2015 to May 2016,the abundance and structure of fishery resources were analyzed.The results showed that the range of dominant species was 3-6(IRI>500),and Oratosquilla Oratoria was the dominant species in 4 months.In terms of relative abundance of fishery species,the minimum value appeared in May 2015,only 451.32ind/h,and the maximum value appeared in August 2015,reaching 11472.33ind/h.During the five months,the relative abundance increased firstly,then decreased,and then increased again,the growth rates were 409.75%,398.67%,-95.63% and129.79%,respectively.In terms of relative biomass,the minimum value appeared in May 2015,only 2.34 kg/h,and the maximum value appeared in August 2015,reaching39.61 kg/h.During the five months,the relative biomass increased firstly,then decreased,and then increased again,which was consistent with trends in relative abundance,the growth rates were 770.43%,94.78%,90.14% and 27.32% respectively.The analysis of the weight per individual of 9 dominant species with commercial economic value showed that the variation of the weight per individual of each species was different.Overall,from spring to winter,the number of dominant species,the abundance and biomass of fishery species,and the commercial value of resources increased first and then decreased,and reached the peak in the summer.The variation trend of the resource structure is in accordance with the characteristics of the fishery resource density and the optimum resource quantity in summer.An analysis of the common species with high contribution rates of similarity within and difference among the five-month Fishery biostation groups in Bohai Sea,China,shows that,,there were Oratosquilla,anchovy,Loliolus Japonica,gobies with a similarity contribution of more than 10%,and there were oratosquilla,anchovy,Loliolus Japonica,gobies with a difference contribution of more than 10%.The difference of similar species within groups and different species among groups with high contribution rate was not significant,and the difference of community structure might be caused by the change of relative resource distribution of the above five species.