Feeding Habit Of Spiny Icefish Chaenodraco Wilsoni In The Bransfield Strait,Antarctica Using Biomarker Techniques And The Influence Factors

There are about 300 marine fish species belonging to 49 families in the Southern Ocean,which represents only c.1.3%of the fish species worldwide.However,compared to the large magnitude of the diversity in the global ecosystem,the diversity of the fish family notothenioids is limited.However,comparably,notothenioids occupy the dominant diversity in the continental shelf habitat.In the offshore area,the ecological function of demersal fish is more important than that of krill.As the main consumer of benthos,it also feeds on zooplankton?mainly krill in summer?,which is the linkage between the upper and lower levels of the food web;they are prey of other fish species,birds and seals.Pelagic fish species?especially lanternfishes?are more abundant than those in the inshore area and play an important role in the energy flow from macrozooplankton to higher trophic levels?such as,seabirds and seals?.However,generally,in the Antarctic marine ecosystem,krill?Euphausia superba?plays the central role in the food web because it is the main food source in terms of biomass for most of the high level predators?from demersal fish up to whales?.In recent years,a krill-independent trophic system has been reported in the open Southern Ocean,or when the biomass of krill is low,fish may act as the linkage between primary producers and higher predators.Spiny icefish?Chaenodraco wilsoni,Regan 1914?is a species of crocodile icefish native to the Antarctic Sound and the tip of the Antarctic Peninsula.It iscommon in the waters around Joinville-D'Urville Islands between the Antarctic Strait and the Antarctic Peninsula,Cosmonauts and Cooperation Seas and the Prydz Bay inthe Indian Ocean.It is the most abundant icefish species in commercial fishing in the past 30 years.Although it is of great significance in biology,the study on the biology of spiny icefish is still not enough.There are few studies on the nutritional dynamics of Antarctic icefish.This limits the understanding of Antarctic fish biology andecology to some extent,and hinders the resource assessment and fishery management of the species.In addition,after the establishment of the Ross Sea region MarineProtected Area,proposals for the construction of marine reserves in other sea areas of the Southern Ocean have been continuously promoted.As one of the main objectives of the construction of marine protected area,how to provide adequate protection for the biological resources of the Southern Ocean,especially the basic research ofimportant fish,is extremely important.Therefore,this paper studies the characteristics of stomach contents,fatty elements and stable isotope composition of spiny icefish in the Bransfield Strait,Antarctica,including species identification and weight,fatty acid contentcomposition,carbon and nitrogen stable isotope composition.Combined withstatistical analysis methods,such as principal component analysis,this paper analyzes and compares its nutritional level,as well as different feeding habits of different body length,seasons and regions.In order to provide useful ideas and basic information for domestic and foreign scholars to carry out Antarctic fish ecology research,and toprovide scientific suggestions for China's participation in the construction of marine protected area.1)29 kinds of fatty acids were detected in muscle tissue of spiny icefish,including 10kinds of saturated fatty acids?SFA?,9 kinds of monounsaturated fatty acids?MUFA?and 10 kinds of polyunsaturated fatty acids?PUFA?.The content of PUFA wassignificantly higher than that of SFA and MUFA,and the content of n-3 fatty acidswas significantly higher than that of n-6 fatty acids in PUFA.In addition,C16:0,C18:0,C18:1n9c,C20:5n3?EPA?and C22:6n3?DHA?were the main fatty acids inmuscle of spiny icefish.2)The content of DHA was significantly higher than that of EPA?t=1.97,P<0.01?,the ratio of DHA to EPA was 1.43,and the ratio of n-6 PUFA to n-3 PUFA was 0.44.According to the health standards proposed by WHO/FAO,it can be regarded as ahigh-quality food for intake of DHA,EPA and n-3PUFA,which has a goodpromoting effect on the development of intelligence and brain,visual development,prevention of nervous system diseases.3)Through the analysis of the special fatty acids,it was found that for Spiny icefish,the contribution rate of grazing food chain was higher than that of detrital food chain,and it mainly showed a planktonic feeding pattern.At the end of summer and thebeginning of autumn,the low level of primary productivity may lead to spiny icefishparticipate in part of the grazing food chain.In addition,they feed less directly orindirectly on dinoflagellates,more on diatoms or diatoms,such as krill,and less onPhytophagous copepods.4)Through the analysis of stable carbon isotope and stable nitrogen isotope,it wasfound that the?¹³C content in the body of spiny icefish was-25.43±1.46‰,whichwas similar to that of C3 plants,and the?¹⁵N content was 8.78±1.16‰.Thestructure of water masses,fronts,currents and other hydrological characteristics inBransfield Strait is unstable and complex,as well as the existence of high primaryproductivity.It is because of the complexity of this habitat that the food source ofspiny icefish is complex.Its carbon source can be traced back to C3 plants on landfor food,and it is a kind of omnivorous fish with high nutritional level.5)Because the Bransfield Strait is controlled by two different water masses?TBWand TWW?,the sea water in TBW area is relatively warm and fresh,while that inTWW area is relatively cold and high salt.Therefore,in the TWW area,spinyicefish showed higher omnivory,while in the TBW area,it was higher carnivorous,which may be related to the dense of krill population in this area.