The Preliminary Study Of Food Composition And Feeding Habit Of Collichthy Lucidus In The Yangtze River Estuary

Collichthy lucidus is a small,demersal,warm water and law salinity fish with higher economic values.C.lucidus is widespread in the world and mainly distributed in the South,East,Bohai and Yellow China sea of Pacific area,and catched in China,Philippine,Indonesia,Japan and Korea.C.lucidus is mainly fresh aquatic products in the coastal area because of its tender meat,rapid growth and wide distribution.C.lucidus is one of the important economic small fish in the Yangtze River Estuary,and with the decrease of traditional economic fish resources and the decrease of predators,the resource of C.lucidus increases year by year.According to the Chinese fishery statistical yearbook,the catches of C.lucidus increases every year,and it reached 409t in 2012 only in the Shanghai area.C.lucidus is relatively key specious in ecosystems in the Yangtze River Estuary which plays an important role in the material flow and energy flow in the whole ecosystem.However,the current reported studies about C.lucidus are less,especially the study of its feeding habit.In this study,C.lucidus samples collected from surveys of bottom trawl in the Yangtze River Estuary from the November 2013 to August 2014.The food composition,feeding habit and nutritional level were studied by stomach contents analysis.The results showed that:1.C.lucidus feed on plankton and zoobenthos in the Yangtze River Estuary,and the sort of food composition are many which number are ten,such as fish,shrimp,crab,isopod,amphipoda,mysidacea,krill,copepods,cladocerans and other food organism.There are 30 species food organism can be identified of C.lucidus.In addition to the normal food organism,C.lucidus were also feeding some rubbish,sediment and fish scales.The niche breadth is big,according to Shannon-Wiener diversity index(H’)and Pielou evenness index(J’)which were 1.8332 and 0.5243 respectively.According to percentage of the relative importance index(IRP/o)and composite indicator dominance index(Ip),shrimp(IRI%=38.45%,Ip=79.03%)and mysidacea(IRI%=36.72%,Ip=7.64%)were the main food of C.lucidus.The main food organism were Palaemon gravieri(IRI%=20.41%,Ip=43.64%),Exopalaemon annandalei(IRI%=14.01%,Ip=27.58%)and Acanthomysis brevirostris(IRI%=30.15%,Ip=6.30%).The intake of fish food organism of C.lucidus was low(IRI%=0.12%,Ip=0.21%)compared with other waters and historicl reseach in the Yangtze River Estuary,which showed that the food composition of C.lucidus appropriate to the spatial and temporal distribution of food organism.2.The feeding habit was influenced greatly by growth and development of fish and seasonal variations.In this study,the feeding habit of C lucidus had significant seasonal variations,with the lowest feeding intensity in Winter and higher in Spring and Summer.The food composition of C.lucidus also had significant seasonal variations that C.lucidus mainly feed on Acanthomysis brevirostris,Palaemon gravieri and Exopalaemon annandalei in Spring and Summer,mainly feed on Acanthomysis longirostris,Acanthomysis brevirostris and Exopalaemon carinicauda in Autum and mainly feed on Palaemon gravieri,Calanus sinicus and Pesudeuphausia sinica.And,the feeding habit C.lucidus was influenced by body length.The feeding intensity was proportional to their body length while the body length of C.lucidus was less than 120 mm,and the intensity decreased when the body length was greater.The predatory capacity and feeding intensity increased with the increased of body length.The feeding frequency of fish in large size was low,and their feeding intensity could be reduced.Small size C.lucidus mainly feed on zooplankton,such as copeods,mysidacea and krill,and large size C.lucidus mainly feed on swimming creatures such as benthic shrimp and copepod,and fish,which consistent with the point of view that "the best feeding theory".3.C.lucidus was carnivorous fish with low nutrition which the year-round average was 3.354.Compared with other waters,C.lucidus was lower in the Yangtze River Estuary,which was mainly related to the low nutrition level of the whole waters.Due to overfishing,the resource of fish decreased in the Yangtze River Estuary recent years.The fish food organism of C.lucidus decreased,and the nutrition level was lower compared with the early sthdies.The nutrition level of C.lucidus had significant seasonal variations,which was lower in summer and winter,and higher in spring and autumn.The nutrition level increased with the growing of body size and the growth and development of C.lucidus.