Feeding Ecology Of Four Commercial Fishes In Zhoushan Islands

Influenced by the Yangtze River water,coastal current,and Taiwan warm current,Zhoushan Archipelago water has high primary productivity and abundant prey.This sea area is the most abundant in fishery resources in China.The feeding ecology and food relationship of marine fish is an important part of the trophic dynamics of marine ecosystems.It is of great academic and practical value to study the feeding ecology of major fish in the waters of Zhoushan Archipelago.In order to compare the differences in ecological niche and resource allocation among different populations of these species,we collected samples of Sebastiscus marmoratus,Nibea albiflora,Collichthys lucidus,and Harpadon nehereus from Zhoushan Archipelago water from 2019 to 2021,and investigated Its food composition and interspecies food relationship,the main results are as follows:（1）Biological characteristicsS.marmoratus’s body length ranged from 21 to 190mm,the average body length was114.18±17.67mm,the body mass ranged from 0.9 to 254.4g,the average body mass was47.83±21.79g,and the average fullness was 3.50±0.49,The relational formula of quality is W=2.96L^3.00.N.albiflora’s body length ranged from 124 to 402mm,the average body length was 275.15±48.36mm,the body mass ranged from 49.0 to 1044.9g,the average body mass was 416.35±196.45g,and the average fullness was 1.89±0.50,The relational formula of quality is W=5.32L^2.81.C.lucidus’s body length ranged from 28 to 165mm,the average body length was 107.28±16.33mm,the body mass ranged from 0.2 to 80.6g,and the average body mass was 23.01±10.79g,and the average fullness was 1.74±0.26,The relational formula of quality is W=1.34L^3.06.H.nehereus’s body length ranged from 14 to 291mm,the average body length was 151.87±43.16mm,the body mass ranged from 0.6 to 198.9g,the average body mass was 27.04±27.78g,and the average fullness was 0.64±2.13,The relational formula of quality is W=3.48L^3.56.（2）Food compositionThe results showed that over 64 prey species were ingested by S.marmoratus.Fishes were the most important pray groups to S.marmoratus,followed by shrimps and crabs,and other species accounted for less.Over 52 prey species were ingested by N.albiflora.Shrimps were the most important pray groups to N.albiflora,followed by fishes and crabs.Over 37prey species were ingested by C.lucidus.Euphausiids were the most important pray groups to C.lucidus,followed by fishes and shrimps.Over 52 prey species were ingested byH.nehereus.Fishes were the most important pray groups to H.nehereus,followed by shrimps and Stomatopod.（3）Characteristics of stable isotopesTheδ¹³C ratios of the four fish species ranged from-24.31‰to-14.41‰,the maximum difference was 9.90‰,the mean was（-17.56±1.91）‰,the mean of S.marmoratus was the bigest,and the mean of C.lucidus was the smallest.Theδ¹⁵N ratios of the four fish species ranged from 7.22‰to 14.09‰,the maximum difference was 6.87‰,the mean was（10.05±1.24）‰,the mean of N.albiflora was the biggest,and the mean of S.marmoratus was the smallest.Except that there was no significant difference between theδ¹³C ratios between N.albiflora and H.nehereus,there were significant differences in theδ¹³C ratios among other fish species.Except that theδ¹⁵N ratio between S.marmoratus and C.lucidus was not significantly different,there were significant differences in theδ¹⁵N ratio between other fish species.Linear fitting of the body lengths of the four fish species and their stable isotopes,Pearson correlation analysis results show that there is a very significant correlation between the body length of N.albiflora and itsδ¹³C ratio,there is a very significant correlation between the body length of S.marmoratus and itsδ¹⁵N ratio.Food source contribution analysis showed that amphipods and zooplankton were the key prey groups for the four fish species.The trophic level calculated based on nitrogen stable isotopes showed that N.albiflora had the highest trophic level,followed by H.nehereus,and S.marmoratus had the lowest trophic level.（4）Interspecies food relationshipThere were significant seasonal differences in the feeding intensity of this four fish species.In terms of feeding intensity,S.marmoratus was the lowest in spring and highest in autumn,N.albiflora was higher in spring and lower in autumn,C.lucidus was higher in summer and autumn,lower in spring and winter,H.nehereus was lower in winter and spring,and higher in summer.S.marmoratus mainly fed on fishes and crabs in spring,crabs in summer,and shrimps in autumn and winter.N.albiflora mainly fed on shrimps and fishes in spring and autumn.C.lucidus mainly fed on euphausiids in spring,summer,and winter,and mainly fed on fishes in autumn.H.nehereus mainly fed on fishes in all seasons.N.albiflora had the widest trophic niche（4.40）,and S.marmoratus had the narrowest trophic niche width（4.01）;H.nehereus had the highest dietary diversity（1.13）,and S.marmoratus had the lowest dietary diversity（0.93）.In terms of the whole year,there was food overlap between S.marmoratus and N.albiflora、H.nehereus,and there was also food overlap between H.nehereus and C.lucidus,but the food competition was not fierce.In spring,there is fierce competition for food from S.marmoratus and N.albiflora;In autumn,there was food overlap between H.nehereus and N.albiflora、C.lucidus.