Selection And Assessment Of The Fish Release Habitat Of Daya Bay

Due to the overfishing and increasingly serious environmental pollution,fishery resources was generally recessing in China.In the late 1950 s,China began to implement the fishery stock enhancement.Years of practice has proved that stock enhancement was an effective pattern to restore the fishery resources.In recent years,there are some problems about the activities of stock enhancement in the Daya Day,the selection of habitats has blindness,which affects the overall benefit of the stock enhancement.This study aims to explore the fish composition and habitat of daya bay,provides technical support for the planning of reserves and the selection of stock enhancement habitats.This study is divided into two parts of selection and assessment of the fish release habitat.The results of the study are as follows:(1)Fish community structure of daya bayTwo fish communities were identified.Group Ⅰwas in the mouth of the Daya Bay,dominated by Leiognathus brevirostris,Apogonichthys lineatus,Apogon kallopterus,Parargyrops edita,Parachaeturichthys polynema and Navodon tessellates,and Group Ⅱ was in within area of the Bay,dominated by Acanthopagrus schlegelii,Parargyrops edita,Leiognathus brevirostris and Navodon tessellates.Significant differences in fish assemblages were found between the two station groups.The canonical coeerspondence analyses(CCA)showed that the water depth,bottom salinity,bottom temperature,pH and DO were the main environmental factors influencing the fish community pattern.(2)Nestedness of fish distribution pattern in daya bay.The community of fish in daya bay was significantly nested.The maximum standard length was significantly correlated with nestedness,indicating that selective extinction is the main driver of nestedness of fish in daya bay.The most friendly sites of the nestedness of four seasons of the year in daya bay are all in the area of yangmei pit(D2),except for spring and winter in the northern area of dalajia island(D5),which was related to the breeding migration.This suggested that the yangmei pit was the main distribution area of fish,deserve priority protection and management,it also showed that this area was the most suitable site for fishery stock enhancement,furthermore,the northern sea area of dalajia island is also very important,it is the spawning ground of fish,and should be protected and managed in spring.(3)Assessment of Saurida tumbil habitat suitabilityThe data collected by four otter trawl surveys in the Daya Bay showed that Saurida tumbil appeared around the dalajia island,especially in the southern and eastern sea area.The range of water depth was 14.00~16.25 m,the range of water temperature was 21.70~24.53 ℃,and the bottom salinity ranged from 34.89 to 36.19.According to HSI model,the area of yangmei pit,and the eastern and southern area of dalajia island were the most suitable sites for Saurida tumbil to live,and they were the best stock enhancement habitats.(4)Assessment of petroleum hydrocarbons pollution in the waters and sediments of the Daya BayThe survey results show that the average pollution index(Ci/Si)of petroleum hydrocarbons is 1.34,according to National Seawater Standard,the concentration limit is Grade Ⅲ,indicating that the seawater has been polluted by petroleum hydrocarbons.The surface sediments of daya bay are not polluted by petroleum hydrocarbon,except the A9 station.The fishes of Daya Bay are clustered in the low petroleum hydrocarbon seas,and the most suitable clustering sites in the four seasons have avoided the high value of petroleum hydrocarbon.The pollution of petroleum hydrocarbons in the waters of Daya Bay has affected the inhabitation of fishes.It is necessary to strengthen the management of water bodies and to protect the Yangmeikeng sea area and the north sea area of Dajiajia island.