Study On The Releasing Of Penaeus Chinensis In Coastal Waters Off Shandong

Penaeus chinensis is the warm water and long-distance migration species. It was the main catch and industries by bottom trawl in Yellow Sea and Bohai Sea, which has very high economic value. In recent years, its yield consistently keep low, because of the severe shortage of spawning broodstock, the inadequate measures of larvae, the poor management of waters and other reasons. In order to protect and restore shrimp production, the state authorities not only strengthen the protection of wild shrimp and the management of sea, but also do the releasing work of shrimp. Since 1984, a lot of the shrimp larvaes were released in the southern coastal waters off Shandong, the southern coastal waters of Bohai Bay and Laizhou Bay on late May to mid-June each year. As to 2010, a total of 15.932 billion shrimp were released by Shandong Province, including 14.854 billion big size which body length is 25～40 mm and 1.078 billion small size which body length is 10～12 mm. Now the catches of shrimp increased significantly.In this paper, according to Penaeus chinensis, the technology and impact of releasing shrimp were studied by using shrimp survey from 2007 to 2010 in Shandong Province, in order to provide Scientiffic basises in the development of reproduction and releasing.The main results as follows:1, The composition of nekton in Laizhou Bay and the southern of Bohai Bay is studied according to the trawl survey data from May 20th to May 30th. The results show that the mean relative catches was 55.8 kg/h,the community structure of nekton are changed and Engraulis japonicus which is the most dominant species become Konosirus punctatus. The community diversity have the increasing trend from the Yellow River to south-east of Laizhou Bay. In addition, the predators of shrimp are studied in Laizhou Bay. The early survival rate of releasing shrimp is maybe affected by Chaeturichthys stigmatias and so on. 2, The paper handled the survey data of Penaeus chinensis in PASW Statistics 18, and output the curves between the body-length and body-weight, get the relations of growth and growth speed from May 17th to October 29th ,2010. We find the L∞and W∞of females are bigger than it in 1984, while males decreased.The growth coefficient K is bigger significantly. The growth of shrimp is more and more earlier and achieve the specifications quickly. The production of shrimp five days in advance or delay have changed because the date of catches by the natural mortality coefficient. When it reached before 5 days, the yield will be lost 7.64%. When it will do after 5 days, the output will be increased 6.76%.3, Based on the bottom trawl surveys in the southern coastal waters off Shandong Peninsula in August 2008,the characteristics of nekton composition was preliminarily analyzed.The results indicated that the mean relative catches was 129.9 kg/h and the dominant species were Engraulis japonicas and Metapenaeopsis dalei.The species composition structure included 3 groups on the level of 35%.Similarity of percentage analysis was used to find?out which species were most responsible for the discrimination between the groups.In this surveys,those species were Metapenaeopsis dalei,Enedrias fangi and Chaeturichthys stigmatias etc which contributed more totally to the average dissimilarity and were discriminators for all between-groups.The fishery resources species were characterized by minimization and low values.4, Based on the recapture surveys of Penaeus chinensis in the southern coastal waters off Shandong from June 16th to August 18th 2009,the result in releasing differnt size of shrimp was preliminarily analyzed.The results indicated that the average growth in length of the small size is 0.73 mm/d on early June, and lower than the large size which is 2.59 mm/d. When it comes to July, the average growth in length of the small size became 0.84 mm/d, and higher than the large size which is 0.47 mm/d. So, the small size needs longer times than big ones to grow in the sea after releasing. The growths of shrimp in the four bays are analysis comparatively and it show that the shrimps in Dingzi Bay and Huangjiatang Bay grow faster than ones in Rushan Bay and Wuleidao Bay and suggest that the size of bay and the waters may be the main factors in the four bays in 2009.5, The recapture of Penaeus chinensis is studied,based on the shrimp surveys in the southern coastal waters off Shandong and Laizhou Bay, 2007 to 2010. The result showed that some changes of recapture rate in two waters during four years. The tatal recapture rate which is 5.73% in Laizhou Bay is higher than it which is 3.92% in the southern waters off Shandong Peninsula. The reason was analysised that the recapture was different. In this survey, recapture rate may be affected by environment of released waters, releasing numbers and releasing size etc.