Spatial And Temporal Variation Of Cultrichthys Erythropterus Feeding Habits In Lake Taihu By Stale Isotope Analysis

Feeding habits of fish could reveal the fish collective action pattern and population changes in fish ecology.Stable isotope technique was feasible for trophic analysis process in aquatic organisms and could reflect the animals feeding habits in current period and even long-term of life activities,and that the results were accurate and no correction.The ?13C values reflected food sources of information and the ?15N values provided nutrition location information.The aim of this study was to explore the feeding habits of Cultrichthys erythropterus by analyzing the changed regularity of ?13C and 815N in four seasons from six areas in Lake Taihu,and discussed influence of population structure change from C.erythropterus on the ecological system,using the stable isotope technology.The study could provide basic data for C.erythropterus feeding habits in Lake Taihu,and further to provide theoretical basis for protection and rational allocation of resource utilization.Specific findings are as follows:1 The time variation of ?13C and ?15N values for C.erythropterus in Lake Taihu.(1)The results showed that the ?13C and ?15N values were positively correlated with the body length(P<0.01 or P<0.05),and the ?13C and ?15N values and the trophic level in large C.erythropterus(>139 mm)individuals are significantly higher than that in the smaller ones(<139 mm)(P<0.05),which indicated C.erythropterus undergo size-related diet shift that switch from small zooplankton to fish due to predation ability strengthening and mouth crack increasing.(2)In addition,the ?13C values of C.erythropterus in summer had obvious difference from the autumn and winter(P<0.05).The ?13C values of C.erythropterus obviously on the low side in summer,showed that C.erythropterus could change feeding habits according to change of food organism in the water.(3)The ?13C and ?15N values had no obvious difference from male and female(P>0.05)in summer,and the cause may be the ingestion had been affected by algae.2 The space variation of ?13C and ?15N values for C.erythropterus in Lake Taihu.(1)The length-weight relationships of C.erythropterus had significant spatial heterogeneity.The groups of C.erythropterus were generally small in center lake area(13.86±2.82 cm)and eastern lake area(8.27±3.34 cm)of Lake Taihu,and population resource obviously tend to be miniaturization.The body length of C.erythropterus had a wide distribution in Dongxi mountain lake area,and the maximum length of C.erythropterus in northern lake area was smaller(19.632 cm)than other lake areas of Lake Taihu.The significant spatial heterogeneity of length-weight relationships may be related to effects of feeding from aquatic-breeding or fishing and it may also be related to certain regional population distribution.(2)The ?13C values of C.eryhropterus had no obvious difference in center lake area and eastern lake area(P>0.05),and were smaller than other lake areas of Lake Taihu.The individuals distribution of C.erythropterus were uniformity and the ?13C values were larger in Dongxi mountain lake area and southern lake area of Lake Taihu,which reflect the different living environment lead to different food.(3)The trophic level of C.erythropterus could increase with the increase of body length.It further proved that the C.erythropterus feeding had a shift phenomenon as the change of body length.3 The trophic level relationships of C.erythropterus and potential food organism.(1)The ?15N values(14.30‰)of Bellamya aeruginosa were higher in Gonghu lake area,and had remarkable difference than other lake areas.The ?15N values(9.12‰)of Bellamya aeruginosa were smaller in northern lake area.It illustrated the Bellamya aeruginosa of the ?15N value associated with a significant external pollution.(2)The trophic level of C.erythropterus was in the highest position in the small fish food web,and main ingested food organisms for POM,small fish and crustaceans,which indicated C.erythropterus undergo size-related diet shift that switch from small zooplankton to fish due to predation ability strengthening and mouth crack increasing.The trophic level of C.erythropterus and potential food organisms had an obvious spatial heterogeneity.It reflected the complexity of the different habitats food web.Research shows that C.erythropterus biased feeding animal bait that had a larger body under the environment of high algae concentration,and relieve the pressure of feeding on zooplankton,so that indirect control of the development of eutrophication.This article also discussed the influence on ecosystem of C.erythropterus,and provided the theory basis resources for its protection and rational allocation of use.