Surveys were conducted in four seasons in the eastern Beibu Gulf from July 2006 to November 2007, to determine the ichthyoplankton composition, abundance, as well as environmental factors impacted on their spatiotempo...Surveys were conducted in four seasons in the eastern Beibu Gulf from July 2006 to November 2007, to determine the ichthyoplankton composition, abundance, as well as environmental factors impacted on their spatiotemporal distributions. The fish eggs and larvae were sorted from 303 zooplankton quantitative samples, in which at least 1 order, 60 families, 31 genera and 61 species of fish eggs and larvae were identified. The species number was highest in summer whereas lowest in winter. With the most abundant fish egg （the average density was 2.41 ind./m3）, spring was the main spawning season, while the greatest mean density of fish larva was 1.35 ind./m3 in summer. In the whole year around, fish eggs had the trends to aggregate in the nearshore of Guangxi coast, fish larvae were more abundant in the northern water. Relationships between fish eggs and larvae abundance and environmental factors were analyzed by using the Yield-Density model. The spatio- temporal distribution of ichthyoplankton in eastern Beibu Gulf was closely related to the Chl a concentration, and the optimal temperature, salinity and Chl a were 19.4-21.7℃, 31.8-33.1 and 1.5-4.8 mg/m3, respectively. Additionally, the distribution of fish larvae could be effected by ocean currents in summer and autumn.展开更多
We conducted acoustical surveys with a horizontal beam transducer to detect fish and with a vertical beam transducer to detect depth and macrophytes in two typical shallow lakes along the middle and lower reaches of t...We conducted acoustical surveys with a horizontal beam transducer to detect fish and with a vertical beam transducer to detect depth and macrophytes in two typical shallow lakes along the middle and lower reaches of the Changjiang(Yangtze) River in November 2013. Both lakes are subject to active fish management with annual stocking and removal of large fish. The purpose of the study was to compare hydroacoustic horizontal beam estimates with fish landings. The preliminary results show that the fish distribution patterns dif fered in the two lakes and were af fected by water depth and macrophyte coverage. The hydroacoustically estimated fish biomass matched the commercial catch very well in Niushan Lake, but it was two times higher in Kuilei Lake. However, acoustic estimates included all fish, whereas the catch included only fish >45 cm(smaller ones were released). We were unable to determine the proper regression between acoustic target strength and fish length for the dominant fish species in the two lakes.展开更多
基金The Chinese Offshore Investigation and Assessment under contract No. 908-01-ST09
文摘Surveys were conducted in four seasons in the eastern Beibu Gulf from July 2006 to November 2007, to determine the ichthyoplankton composition, abundance, as well as environmental factors impacted on their spatiotemporal distributions. The fish eggs and larvae were sorted from 303 zooplankton quantitative samples, in which at least 1 order, 60 families, 31 genera and 61 species of fish eggs and larvae were identified. The species number was highest in summer whereas lowest in winter. With the most abundant fish egg （the average density was 2.41 ind./m3）, spring was the main spawning season, while the greatest mean density of fish larva was 1.35 ind./m3 in summer. In the whole year around, fish eggs had the trends to aggregate in the nearshore of Guangxi coast, fish larvae were more abundant in the northern water. Relationships between fish eggs and larvae abundance and environmental factors were analyzed by using the Yield-Density model. The spatio- temporal distribution of ichthyoplankton in eastern Beibu Gulf was closely related to the Chl a concentration, and the optimal temperature, salinity and Chl a were 19.4-21.7℃, 31.8-33.1 and 1.5-4.8 mg/m3, respectively. Additionally, the distribution of fish larvae could be effected by ocean currents in summer and autumn.
基金Supported by the Special Scientific Research Fund of Agriculture Public Welfare Profession of China(No.201303056)the State Key Laboratory of Freshwater Ecology and Biotechnology(No.2011FBZ28)the Science and Technology Research Project of China Three Gorges Corporation(No.CT-12-08-01)
文摘We conducted acoustical surveys with a horizontal beam transducer to detect fish and with a vertical beam transducer to detect depth and macrophytes in two typical shallow lakes along the middle and lower reaches of the Changjiang(Yangtze) River in November 2013. Both lakes are subject to active fish management with annual stocking and removal of large fish. The purpose of the study was to compare hydroacoustic horizontal beam estimates with fish landings. The preliminary results show that the fish distribution patterns dif fered in the two lakes and were af fected by water depth and macrophyte coverage. The hydroacoustically estimated fish biomass matched the commercial catch very well in Niushan Lake, but it was two times higher in Kuilei Lake. However, acoustic estimates included all fish, whereas the catch included only fish >45 cm(smaller ones were released). We were unable to determine the proper regression between acoustic target strength and fish length for the dominant fish species in the two lakes.
