No abstract

Isopods are parasitic crustaceans that pose serious threat to fisheries. Several studies have tried to explore the host-pathogen relationship between marine fishes and isopods. The present study aims to understanding the secondary infections in marine fishes pertaining to isopods. To assess the secondary infection in infected fishes, parasite infested and healthy tissues of fishes were collected. The samples were subjected to standard microbiological procedure to identify the presence of pathogenic bacteria and fungi. Our results showed the branchial region had the higher microbial load of non-sporulating cenocytic fungi in infected fishes. Moreover, fungal strains isolated from the parasitic lesion confirmed that the parasitation and body lesion facilitates the entry of several pathogenic microbes at the damaged host tissue. More over the immune regulation of fish fights back by producing minute cysts, trying to encapsulate the growing fungus. But this may eventually lead to systemic infestation and death of the fish.

The study was aimed to evaluate the effect of formalin preservatiion on the shape, size and condition factor of the freshwater silurid catfish Wallago attu (Bloch and Schneider, 1801) using length-weight relationship (LWR), condition factor and truss analysis. A total of 50 specimens of the fish were procured from the river Ganga at Kanpur region. The fresh and formalin preserved fish were measured for total length, standard length and body weight. Results of LWR revealed that the fresh and preserved fish followed different growth pattern and cube law. High values of r 2 were obtained for the relationship between length and weight of the fish before and after preservation of the fish in formalin. Decrease in length and an increase in weight was observed in the preserved specimens of the fish due to the effect of formalin but were not statistically significant. The mean condition factor (K) showed significant (p<0.05) change in the fish after preservation. The univariate and multivariate analysis of truss measurements, two partially overlapping different convex hulls of the scatter plot of PC1 on PC2 and canonical discriminant functions showed highly significant morphometric heterogeneity between the specimens of fresh and preserved fish. The results of the present study suggest that fresh specimens of the fish should be used in research studies based on weight and linear body measurements of the fish.