| Fishery resources were abundant in the waters of Zhoushan Islands.However,due to the influence of fishing intensity and human activities,many wild economic fish resources decline sharply,fish community structure and food web structure and function have also changed.Enhancement and release are effective way to recover fishery biological resources.Larimichthys crocea,Oplegnathus fasciatus and Sepiella maindroni are all important species of Enhancement and release in this area.Feeding ecology research is an important aspect of the trophic dynamics of marine ecosystems.The research on the feeding ecology of the main enhancement and releasing species is conducive to exploring the changes in the structure and function of the ecosystem after the resource changes,and provides a basis for the evaluation of the effects of enhancement and releasing,which has important academic and practical significance.Therefore,in this study,L.crocea,O.fasciatus and S.maindroni collected from trawls,gillnets and fishing surveys in Zhoushan Islands from March 2021 to November 2022 were selected as research objects.Combined with the stomach contents analysis and carbon and nitrogen stable isotope analysis,the feeding ecology was preliminarily studied and related food chains were constructed.The main results are as follows:(1)Food composition and feeding intensityThe results showed that 54 prey species were ingested by L.crocea,including Pisces,Decapoda,Stomatopoda,Euphausiacea,Mysidacea Crabs,etc.The most important prey species of L.crocea were Euphausiacea,Acetes chinensis,Oratosquilla oratoria,Benthosema pterotum,Acropoma japonicum and Harpadon nehereus.The empty stomach rate and stomach fullness index of L.crocea were 56.9%and 1.8.The feeding intensity of L.crocea was highest in summer and lowest in spring and winter,and the mean stomach fullness index decreased with the increase of body length.There were extremely significant differences in stomach fullness index of L.crocea in different seasons and body length(P<0.001).We identified 61 prey species were ingested by O.fasciatus,including Amphipodas,shrimp and crabs,Echinodermata,Mollusks and Macroalgae,etc.The most important prey species of O.fasciatus were Amphipodas.The empty stomach rate and stomach fullness index of O.fasciatus were 40.91%and 3.5.The feeding intensity of O.fasciatus was highest in summer and lowest in winter,and the mean stomach fullness index increased with the increase of mantle length.There were extremely significant differences in stomach fullness index of O.fasciatus in different seasons and body length(P<0.05).The S.maindroni mainly feed on seven groups including Pisces,Decapoda,and Brachyura,among which shrimp account for the largest proportion(IRI%=31.97%),followed by crabs(IRI%=35.28%)and fish(IRI%=26.03%).The feeding intensity of S.maindroni was highest in summer and lowest in spring,and decreased with the increase of fork length as a whole.There were extremely significant differences in stomach fullness index of S.maindroni in different seasons and mantle length(P<0.05).(2)Characteristics of stable isotopesThe δ13C ratios of three species ranged from-20.36‰ to-15.17‰,with the maximum difference of 5.19‰ and the mean of(-16.96±0.86)‰,the mean of L.crocea was the highest(-16.74±0.83)‰,and the mean of O.fasciatus was the lowest(-17.19±0.98)‰.Theδ15N ratios of the three species ranged from 7.72‰ to-13.24‰,with the maximum difference of 5.52‰ and the mean of(10.03±1.07)‰,the mean of L.crocea was the highest(10.63± 1.06)‰,and the mean of O.fasciatus was the lowest(9.34±0.67)‰.Pearson analysis showed that the δ13C value of muscle was not significantly correlated with the mantle length,but the δ15N value was significantly positively correlated with the the mantle length(P<0.01).Pearson correlation analysis showed that the δ13C ratio was negatively correlated with body length of L.crocea,and the δ15N ratio was positively correlated with body length of all three species.The contribution rate of food source based on Mixsiar showed that the contribution rate of Zooplankton to L.crocea was the highest,followed by Shrimp and crab.The contribution rate of Macroalgae to O.fasciatus was the highest,followed by Amphipoda.Shellfish contributed the most to the S.maindroni,followed by Zooplankton.Siber model analysis showed that TA(total area),SEA(Standard Ellipse Area)and SEAc(the corrected version of the Standard Ellipse Area)of L.crocea were the largest.The three species occupied different trophic niche areas that were overlapping.(3)Food chain structureUsing Zooplankton as the baseline,the trophic levels of the three species and their prey species were calculated.The results showed that the trophic levels of L.crocea,O.fasciatus,S.maindroni were 3.73±0.27,3.31±0.20 and 3.60±0.30,respectively.The average trophic levels of prey species ranged from 2.08 to 3.93.Among them,the trophic level of Loligo beka was the highest and that of Caprellidae was the lowest.The carbon source contribution rates of Macroalgae,phytoplankton,POM(suspended particulateorganic matter),and SOM(sediment organic matter)to prey species were calculated,and the related food chain relationships were established.The results showed that phytoplankton and SOM were the main carbon sources,followed by macroalgae,and POM had the smallest contribution.The main carbon source of small fish,cephalopods and zooplankton is phytoplankton.The main carbon sources of shrimp were macroalgae and SOM.Major carbon sources for other consumer groups are macroalgae,phytoplankton and SOM.Based on the analysis results of stable isotopes and stomach contents in this study,it can be seen that there are several major food chains existed in the three species:one is the detritus food chain of macroalgae,SOM-gastropod or amphipoda-shrimp and crab-L.crocea and S.maindroni.The second is the grazing food chain of macroalgaegammaridea and gaprellidae-O.fasciatus.The third is the grazing food chain of phytoplankton and POM,etc-zooplankton-planktivorous fish such as Engraulis japonicus and B.pterotum-L.crocea and S.maindroni. |
PDF Full Text Request