Biodiversity Investigation Of The Setnet In ShaZiKou Bay And Neighbouring Waters

The paper is based on the setnet catch data in ShaZiKou Bay and its neighbouring waters from May, 2006 to May, 2007. There were 99 species recorded. The catch composition of the setnet fishing gear were analyzed, the seasonal variations of biodiversity were analyzed. The results showed that the catches in the study area consisted of juveniles of the commercial fishes, small low-value fishes, and commercial invertebrates. The fish sizes were generally small. On the basis of the results, we made some suggestions to conserve the near-shore biodiversity and to rationally utilize the coastal fishery resources.The most important results are as follows:(1) There are 98 species recorded in the ShaZiKou Bay and its neighboring waters, including 56 fish species, 28 crustacean species , 6 cephalopod species and 8 other species.(2) In this investigation, 56 fish species are caught, with warm temperature species, warm water species and cold temperature species accounting for 47.0%, 32.0% and 21.0%. The settling species and the migratory species account for 52.0% and 48.0%. The pelagic species accounts for 16.0%, while the demersal species amounts to 84.0%. 28 crustacean species are caught, and the main species are Trachypenaeus curvirostris, Palaemon gravieri, Alpheus japonicus, Alpheus heterocarpus and charybdis bimaculata. 6 cephalopod species are caught, and the main species are Octopus ocellatus ,Octopus variabilis and Loligo japonica.(3) The dominant species in the study area consist of small low-value fishes (such as Engraulis japanicus, Thryssa kammalensis, Ammodytes personatus, Enedrias fangi etc.),commercial invertebrates (such as Trachypenaeus curvirostris, Palaemon gravieri, Octopus ocellatus, Octopus variabilis) and juveniles of commercial fishes (such as Pseudosciaena polyactis, Argyrosomus argentatus). These dominant species appear by turns. They make up the most catches in the fishing seasons. (4) The number of species are the largest in August 2006, with the number of 31, while the number of species are the smallest in December 2006 with the number of 20. The species richness index (D) is highest in June 2006 (2.927) and lowest in September 2006 (2.200). When it comes to Shannon-Wiener index (H'), the highest value appears in January 2007 (2.479), and the lowest value appears in May 2006 (1.673). When the species evenness index (J') is concerned, it is highest in December 2006 (0.800) and lowest in May 2006 (0.533).(5) The length composition and weight composition of the catch are studied. The results show that the sizes of individuals of Pseudosciaena polyactis, Johnius belengeri, Chelidonichthys kumu, Trachypenaeus, Oratosquilla oratoria are very small, most of which are juveniles and small shrimps.