Helminth communities of fish as ecological indicators of lake health.

This paper deals largely with the dynamics and changes in the helminth parasite communities of fish along the trophic gradient of lakes. The use of parasitological community data as a bioindicator of environmental health underlines the need to study parasite communities at comparable localities with known pollution levels. The comparison of the conditions in different habitats might be helpful to differentiate between normal fluctuations in ambient conditions and pollution-mediated effects. Therefore, the present study was designed to examine the community structure of parasites in snow trout (Schizothorax niger Heckel) inhabiting 3 lakes of contrasting trophic status in Kashmir. The idea of selecting the lakes, namely Anchar (strongly hypereutrophic), Dal (eutrophic) and Manasbal (mesotrophic) for this study was intentional as they depict different trophic gradients and exhibit the desirable pattern which was a prerequisite for this study. The findings presented in this article suggest an apparent lake-wise gradient in community structure, as the increase in trematode and cestode infections in Anchar was markedly greater, to levels clearly distinguishable from those in the other two water bodies. We conclude that human-induced eutrophication of lakes modifies the parasite community at component level and community-level studies on parasites may provide information on health status of lakes.

Seasonal changes in infrapopulations of Diplozoon kashmirensis Kaw, 1950 (Monogenea: Diplozoidae) along a eutrophic gradient.

Seasonal population dynamics of the monogenean, Diplozoon kashmirensis Kaw, on the gills of two cyprinid fish species, Schizothorax niger Heckel and Carassius carassius (Linnaeus), was investigated in three limnologically distinct trophic habitats located along the flood plain of River Jhelum in Kashmir from June 2006 to May 2008. The parasite infrapopulations exhibited a marked seasonal regime in infestation pattern as the infection indices increased to a much higher plateau during summer season at all the lakes, while the lows were recorded in winter. The heterogeneity in infection pattern indicates that water temperature is an important determinant of the seasonality of infrapopulations at all the localities. Furthermore, the results of our work clearly indicate that the parasite infrapopulations increased proportionally with eutrophication level and, as such, the highly eutrophic habitat, Anchar Lake, was significantly more favourable for parasite infrapopulations than the less eutrophic ones. However, the lakes presented no significant interlake differences in water temperature. Therefore, we could argue that interlake differences in the infestation pattern of parasite can be safely attributed to respective water quality in the lakes rather than water temperature. We propose that infrapopulations of the diplozoid studied herein do respond to differences in water quality of lakes and, thus, could qualify as simple and reliable indicator species in short-term comparative assays by lake managers.

Metacercariae of Clinostomum schizothoraxi Kaw, 1950 (Digenea: Clinostomatidae) in Carassius carassius (Linnaeus) under different environmental conditions.

This report addresses the possible impacts of local habitat characteristics on the metacercariae of Clinostomum schizothoraxi Kaw, 1950 infecting crucian carp, Carassius carassius (Linnaeus), from three lakes in Kashmir. The lakes chosen encompass an extremely wide gradient in trophic status--Manasbal (less polluted and mesotrophic), Dal (moderately polluted and eutrophic) and Anchar (strongly polluted and hypertrophic). The results indicate that infrapopulation-level descriptors of abundance of C. schizothoraxi in fish differed between the three lakes and revealed that the infection levels were greater at Anchar Lake. Furthermore, the prevalence, mean abundance and mean intensity of infection also changed during the period of investigation along the seasonal gradient of water temperature. The fact that the abundance patterns of the parasite differed in different populations of the same host provided a unique opportunity for a comparative study on the temporal variations in infection patterns attained during different seasons. In particular, the lake environments showed a high degree of variability in the density profiles of mollusc intermediate hosts and, thus, the differences in the infection status of crucian carp were derived on the basis of intermediate host population size which, in turn, was influenced by the trophic characteristics of the three lakes.