Impact And Assessment Of Reclamation Project On Fish Resources In Tianjin Coastal Waters

Tianjin’s coastal waters are located at the western end of the Bohai Bay.Historically,the sea is rich in fishery resources.It is the spawning ground for many migratory fish,breeding grounds and feeding grounds.However,affected by reclamation projects and other human activities,fisheries resource structure in Tianjin coastal waters has undergone major changes.Based on the survey data of 2017 and2018,this study conducted a preliminary study on the fish community structure in the coastal waters of Tianjin,and combined the relevant data to analyze the impact of the Tianjin reclamation project on fish communities and its resources estimate.The main findings are as follows:A total of 26 species of fish were captured during the survey,of which 23 species were captured in 2017 and 2018,and there was no significant difference in fish species composition between regions and years.The dominant species of fish are mainly composed of small fish such as Chaetueichthys stigmatias and Clupanodon punctatus,and the dominant species are slightly different between regions and years.The annual average relative density of fish varies significantly between regions and years;the annual average relative biomass is not significantly different between regions,and the difference between years is significant.The results of CLUSTER and MDS analysis showed that there were differences in fish community structure between the reclamation area and the nearby sea area.A total of 3 orders and 5 families of fish eggs were collected in June in the 2017survey;A total of 5 orders and 8 families of fish eggs were collected from April to September in 2018.The number of fish eggs was not significantly different between different regions,and the difference was significant between different years.A total of3 orders 4 families and 5 species of larvaes were collected in the 2017 survey.A total of 9 species(genus)of larvaes were collected from May to August and November in2018.The number of larvaes were not significantly different between different regions and different years.The annual average relative density of fish eggs and larvaes were significant in different sea areas and different years.The species diversity index of fisheggs and larvaes were different between regions and years.The results of CLUSTER and MDS analysis showed that the community similarity between fish eggs and larvase were low,forming different niches.Based on the 2006 and 2008 survey data,the loss of fish resources before and after the completion of the reclamation project was evaluated.After reclamation,the number of fish species in Tianjin sea area decreased by 34 species,the resource volume decreased by 75.45%;the number of species of fish eggs decreased by 11 species,the resource decreased by 95.07%;the number of species of larvaes decreased by 12 species,and the resource decreased by 94.89%.The reclamation project resulted in an annual loss of fish resources of 302.3 t,fish eggs 17.24×108 ind and larvaes 11.96×108ind in Tianjin coastal waters.The direct economic loss was as high as 89.132 million yuan.The survey compared before and reclamation,reducing the number of types of fish 27 species,resources fell 94.95%;fish eggs and larvaes resource loss rate as high as 86.09%;The center of gravity of the fish farm and the center of gravity of the spawning ground are transferred to the southeastern offshore.By measuring the Clupanodon punctatus,Setipinna taty,Engraulis japonicus and Lateolabrar japonicus,based on the analysis of body weight-body length relationship and age composition,it was found that the offshore fish community in Tianjin is mainly composed of small and young fish.The body length-weight relationship of the 4 economic fishes has a good fitting effect,which can accurately reflect the body mass relationship of the current sample fish in Tianjin.The bait group analysis of the 26 species of fish caught,the results show that the bait group analysis of the 26 species of fish caught showed that the fish community consisted of six functional groups,namely shrimp/fish predators,piscivores,benthivores,zooplanktivores,generalist predators and omnivorew.According to the catch composition,the main functional groups in Tianjin coastal waters are omnivorew,shrimp/fish predators and zooplanktivores functional groups.