HOST RELATIVE CONDITION FACTOR AND THE PREVALENCE OF INTESTINAL PARASITES OF PARACHANNA OBSCURA AND SAROTHERODON MELANOTHERON AS INDICATORS OF ENVIRONMENTAL STRESS IN LEKKI LAGOON, LAGOS, NIGERIA

Abstract

Condition factor is a measure of energetics, nutritional status and viability of a host. Changes in the host condition factor have effect on the rate of infection. 100 fishes of Sarotherodon melanotheron and 90 of Parachanna obscura from the Lekki lagoon were procured and dissected for intestinal helminth parasites. Condition factors of all individuals were determined. Median condition (K < 1.32 and K > 1.32) for Parachanna obscura and (K < 4.09 and K > 4.09) for Sarotherodon melanotheron were used in grouping the individuals. Male and female individuals of low condition factor (K < 1.32) and (K < 4.09) had very low parasite prevalence, 5.55% to 8.69% compared to male and female individuals of high condition (K > 1.32) and (K > 4.09), having a prevalence of 13.64% to 30.43%. These percentages were expressed in the various parasite groups in the population. The exception to these, were the female individuals of Sarotherodon melanotheron of low condition status (K = 3.93±0.11) that had a percentage prevalence of 35.71% for Clinostomum sp. These individuals had a more stable condition but compromised immunological status. Changes in the environment, both anthropogenic and environmental, can alter host/parasite equilibrium and cause disease or mortality in fish. The infected individuals of low condition status showed bile stasis within the liver parenchyma, under histopathological examination. Decrease or increase in parasite prevalence as a result of poor health condition of the host is an indicator of environmental stress. Monitoring health condition of fish population provides vital information for ecotoxicologist and toxicologist for improved environmental monitoring.