Analysis On The Difference Of Feeding Ecology Of Dosidicus Gigas In The High Seas Of Ecuador And Peru

In this study,we selected the Dosidicus gigas in the high seas of Ecuador and Peru in the eastern Pacific Ocean as the research object.Through the identification and measurement of the otoliths and cephalopods beaks residul in the stomach of D.gigas,we analyzed the differences in feeding composition and feeding habits at different life stages in different sea areas.and exploration the differences of carbon and nitrogen stable isotopes and fatty acid compositions in muscle tissue of the D.gigas in the two sea areas.Stable isotope technique was used to analyze the effects of mantle length andgonadal maturation on feeding habits of D.gigas,and compare the ecological niche differences between the two sea areas and exploration the differences in feeding habits of D.gigas in the different seas.The difference of fatty acid composition was used to analyze the feeding difference in the life cycle stage.The results are as follows:（1）As one of the important methods,stomach contents analysis method can quickly instruction predators feeding preferences of feeding process,the hard tissuse of otoliths and cephalopods beaks residual in the stomach difficult to corrode,which play an important role in identification of stomach contents,and fish otolith,cephalopods beaks length can reveals the length of prey,enrich the cephalopods feeding study.Through the identification of stomach contents of D.gigas,the result showed that main preys species of D.gigas in the high seas of Ecuador including 7 kinds of fish and 4kinds of cephalopods,Vinciguerria lucetia,Diogenichthys laternatus,Triphoturus mexicanus as the dominant prey species.main preys species of D.gigas in the high seas of Peru including 6 kinds of fish and 2 kinds of cephalopods,V.lucetia,D.laternatus and Bregmaceros bathymaster as the dominant prey species.Prey number of D.gigas in the high seas of Ecuador was higher than that in the high seas of Peru.With the increase of mantle length of D.gigas,the number and body length of prey were increased.In the high seas of Ecuador the body length of V.lucetia increased with the mantle length of D.gigas while the body length of other fish species did not change.In the high seas of Peru,there was no change of prey body length with the mantle length of D.gigas increase.In the high seas of Ecuador and Peru,the mantle length range of cephalopods prey from 20 to 90mm,Dosidicus gigas was the biggest cephalopods prey of D.gigas,Feeding habits and feeding strategies of D.gigas change in different stages of life cycle.（2）As an important ecological method,stable isotope technology plays an important role in the study of aquatic organisms’feeding habits and habitat environment.The article analyzed the stable isotope of the muscles of the D.gigas samples collected by the Chinese squid fishing boat during the production in the high seas of of southeast Pacific from June to December 2019,using stable isotope technology to analysis its feeding habit,The results showed that the range ofδ¹³C of muscle ofthe D.gigas in the high seas of Ecuador from-19.81 to-17.38‰,the range ofδ¹⁵N from 9.36 to 14.43‰;theδ¹³C range of D.gigas in the high seas of Peru from-20.77 to-17.99‰,and the value ofδ¹⁵N ranges from 7.65 to 13.60‰,Theδ13C andδ¹⁵N of D.gigas muscles in the high seas of Ecuadorare significantly higher than those in the high seas of Peru（P<0.05）.using generalized additive models（GAM）to analyze the influence of mantle length of D.gigas onδ¹³C andδ¹⁵N of muscle,the results show thatδ¹³C andδ¹⁵N of muscles of D.gigas in the high seas of Ecuador were not significantly correlated with mantle length（P>0.05）,while the musclesδ¹³C andδ15N of D.gigas in the high seas of Peru were significantly related to mantle length（P<0.05）.The effects of mantle length onδ¹³C andδ¹⁵N of female and male individuals of D.gigas in the two regions were different.Meanwhile,δ¹³C andδ¹⁵N of D.gigas also changed with the sexual maturation,A low trophic niche（SEAc=1.46²‰）of D.gigas in the high seas of Ecuador has affected by the isotope baseline and feeding effect,The muscleδ¹³C andδ¹⁵N of D.gigas have no difference in mantle length.A high trophic niche（SEAc=2.18²‰）of Dosidicus gigas in the high seas of Ecuador（SEAc=2.18²‰）affected by the feeding effect,muscleδ¹³C andδ¹⁵N differ greatly in mantle length.Both in two seas,female of D.gigas has a high trophic niche.（3）As the main component of lipids,fatty acids are essential nutrients for marine animals as well as the main source of energy for the body.A total of 28 kinds of fatty acids were detected in the muscles of D.gigas in the high seas of Ecuador and Peru.including 10 kinds of saturated fatty acids（SAT）,8kinds of monounsaturated fatty acids（MUFA）and 10 kinds of polyunsaturated fatty acids（PUFA）,the dominant fatty acids were PUFA in the both two seas,Principal Component Analysis show that the fatty acid of D.gigas has the spatial difference,C20:4n6 is an important reason for the difference of fatty acids in the high seas of Ecuador and Peru..Principal Component Analysis show that the fatty acid of D.gigas has the spatial difference,C20:4n6 is an important reason for the difference of fatty acids in the high seas of Ecuador and Peru.The difference of PUFA/SFA of D.gigas in the sea area suggests that there may be a relatively rich food resource in the high seas of Ecuador.The difference of fatty acids of D.gigas in the sea area may be due to the joint influence of the difference of the sea environment and the feeding effect.Through the study on the difference（P<0.05）of feeding habits of D.gigas in the southeastern Pacific,Dosidicus gigas have different feeding habits and strategies in different life history stages and different habitats.At the same time,these research results can provide a certain reference for the study of cephalopod feeding.