Infection dynamics of Caryophyllaeid tapeworm, Adenoscolex oreini Fotedar, 1958 and impacts of intra-lake pollution gradient on intermediate host (copepods) and health attributes of Schizothorax spp.

Abstract

SUMMARY This study is an attempt to unravel the infection pattern of the Caryophyllaeid tapeworm, Adenoscolex oreini and its association with water quality, planktonic copepods and health traits of fish in a highly stressed lake. Prevalence differed significantly (P < 0·05) among different fish species with highest infection recorded in Schizothorax niger (% = 36·74) compared to Schizothorax esocinus (% = 15·7). Within-lake trophic gradient affected the infection pattern as prevalence of A. oreini was significantly higher (44·62%, P = 0·0001) at hypereutrophic site as compared to least eutrophic site (8·01%). The data suggest that spatial variation in the intensity of A. oreini corresponded to the variation in the abundance of planktonic copepods. The density of Cyclops scutifer was positively correlated with the prevalence of tapeworm. Results indicate that the health condition, which was reflected by condition factor and gonadosomatic index, was lower in parasitized fish, and there seems to be synergistic effect of eutrophication and parasitism on fish health. Linear regression coefficients showed that the health indices were significantly (P < 0·05) predicted by infection intensity. It is concluded from the results that within-lake pollution gradient affects the infection pattern, density of intermediate host and health attributes of fish, and therefore these finding will lead us to elucidate the predictors responsible for decline of health of fish in highly stressed water bodies.