| Silver carp,Hypophthalmichthys molitrix,has been one of the most important traditional freshwater aquaculture species in China.The Yangtze River and its attached water bodies are main genetic resources banks to silver carp in which the germplasm are superior to those in other water bodies.Therefore,it is necessary to assess the stock resources of silver carp in the Yangtze River Basin.Otolith is a metabolically inert calcium carbonate that can record the environmental history throughout fish life.In the current study,the spawning period of silver carp from the Yangtze River,Ganjiang River and Poyang Lake were analyzed.The eight elements in the otolith core elements and the otolith edge elements(Sr,Ba,Na,Si,Cr,Mn,Ca,Zn)of young-of-the-year(YOY)silver carp collected during August-September of 2012,2014,and 2016 from the Yangtze River and Ganjiang River were analyzed using laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS).The fingerprints of the environmental elements that can be used to identify the silver carp stocks of the Yangtze River and Ganjiang River were analyzed.At the same time,the eight elements in the otolith core elements(Sr,Ba,Na,Si,Cr,Mn,Ca,Zn)of YOY silver carp collected during August-September of 2012,2014,and 2016 from the Poyang Lake were analyzed LA-ICP-MS,the source of the silver carp stocks in Poyang Lake was analyzed.The eight elements in the core elements of adult silver carp from Yangtze River,Ganjiang River and Poyang Lake were analyzed,in order to provide basis provide basic information for protecting silver carp resources in the Yangtze River.The main results were as follows:1.According to the number of silver carp otolith daily increment and the collection date that collected from the Yangtze River,Ganjiang River and Poyang Lake,calculated the spawning period of Yangtze River silver carp stocks from May 30 to July 18,mainly concentrated in late June and early July;back calculated the spawning period of Ganjiang River silver carp stocks from May 18 to July 20,mainly concentrated in early June;back calculated the spawning period of the silver carpstocks collected from Yongxiu from May 18 to July 20,mainly concentrated in early June;back calculated the spawning period of the silver carp stocks collected from Yugan from May 17 to July 18,mainly concentrated in early June and in late June;back calculated the spawning period of the silver carp stocks collected from Boyang Lake from June 12 to July 1,mainly concentrated in late June;back calculated the spawning period of the silver carp stocks collected from Hukou from May 25 to July20,mainly concentrated in late June and early July.2.The trace elements in the otolith core of the YOY siver carp from the Yangtze River and Ganjiang River in 2012,2014 and 2016 were measured and analyzed.The ratios of the four trace elements to the calcium(Sr:Ca,Ba:Ca,Si:Ca,Mg:Ca)in the otolith core and edge of YOY silver carp from the Yangtze River and Ganjiang River were consistent.It was showed that the ratios of the four trace elements to the calcium(Sr:Ca,Ba:Ca,Si:Ca,Mg:Ca)in the otolith core of the YOY silver carp in the Yangtze River and Ganjiang River was basically unchanged from the same river.However,there was a significant difference between the two stocks from the Yangtze River and Ganjiang River and the ratios of Si:Ca and Sr:Ca made the greatest contribution to stock identification.According to the linear discriminant analysis(LDFA)of the four element ratios,the overall classification accuracy rate of Yangtze River silver carp stock was 92.11%,7.89% cannot distinguish its source,and the classification accuracy rates in 2012,2014 and 2016 were 92.31%,93.33% and 90.91%,respectively.The overall classification accuracy rate of Ganjiang River silver carp stock was 92.31%,7.69% cannot distinguish its source,and the classification accuracy rates in 2012,2014 and 2016 were 80.00%,96.77% and 93.75%,respectively.Thus,the four element ratios in otolith core could be used as elemental fingerprints to identify silver carp stocks from the Yangtze River and Ganjiang River.Analysis of otolith microchemistry by LA-ICP-MS will be an effective technique in stock discrimination such as silver carp from the Yangtze River and Ganjiang River.3.The trace elements in the otolith core of the YOY siver carp from Poyang Lake in 2012,2014 and 2016 were measured and analyzed.The results showed that39.39% the silver carp in Poyang Lake came from the Yangtze River and 51.52% ofthe siver carp came from the Ganjiang River,but 9.09% cannot distinguish its source.Among them,the proportions of silver carp in Hukou,Boyang,Yongxiu,Yugan,and Duchang groups come from Yangtze River were 86.21%,29.63%,19.23%,12.00%,44.00%,respectively;the proportions of silver carp in Hukou,Boyang,Yongxiu,Yugan,and Duchang groups come from Ganjiang were 6.90%,62.96%,69.24%,72.00%,52.00%,respectively,but 6.89%、7.41%、11.53%、16.00%、4.00% cannot distinguish its origin.The YOY silver carp collected from Hukou that near the Yangtze River mostly came from the Yangtze River,while the YOY silver carp collected from other waters of Poyang Lake came from the Ganjiang River.4.The trace elements in the otolith core of the adult siver carp from Yangtze River,Ganjiang River and Poyang Lake were measured and analyzed.Linear discriminant analysis(LDFA)was used to determine whether the adult silver carp in the Yangtze River come from the Ganjiang River or the the silver carp in the Ganjiang River come from Yangtze River,including the proportion of silver carp in Poyang Lake come from Yangtze River and Ganjiang River.The results showed that 15.38%of the adult silver carp in the Yangtze River originated from the Ganjiang River,7.69% of the adult silver carp in the Ganjiang River originated from the Yangtze River,the proportion of adult silver carp collected from Poyang Lake originated from the Yangtze River and Ganjiang River was 20.00%,33.33%,respectively.It showed that silver carp in the Yangtze River and Ganjiang River could exchange information,and the silver carp in the Yangtze River can enter Ganjiang River to breed,and the silver carp in Ganjiang River can also enter the Yangtze River to breed.In summary,the four elemental fingerprints(Sr:Ca,Ba:Ca,Si:Ca,Mg:Ca)are the environmental element fingerprints that effectively identify the stocks of the Yangtze River and the Ganjiang River.Silve carp in Poyang Lake came from the Yangtze River and the Ganjiang River,mostly came from the Ganjiang River,and silver carp in Yangtze River and Ganjiang River could exchange information through Poyang Lake. |
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