Prevalence and Intensity of Parasites in Edible Fishes Landing at Karachi Fish Harbour

The fish randomly picked from the fish lot lying in the hall of the Karachi Fish Harbour for auction were examined for a period of one year from August 2007 to July 2008 to find out the prevalence and intensity of parasites in different species. Out of 44 species of fish examined, 22 species were found to be infected by parasites and a small sciaenid Johnieops sina (Cuvier, 1829) was highest in numbers. Among the total number of 263 fish specimens examined for parasites, 47 fish (17.9% of the total sample) were infected. Prevalence of infection was found almost throughout the year with the exception of May 20007, when the average seawater temperature was 27.9 degrees C. The highest prevalence of infection was observed in October 2007 when the average seawater temperature was 29.5 degrees C. There was no correlation between seawater temperature and prevalence of parasitic infection (r = 0.102; P > 0.05). In the present study, among the infected fish, 78.7% were found to be infected by nematodes and 21.3 % by trematodes. The nematode varied from 1 to 12 in numbers per fish. The highest number of nematode (12) were recorded in April'08 in deep flounder, Pseudorhombus elevatus Ogilby 1912 (TL = 20.0 cm), when the average seawater temperature was 28.4 degrees C. The trematode varied from 1 to 4 in numbers per fish. The highest numbers of trematodes (4) were recorded in September'07 in malabar trevally, Carangoides malabracius (Bloch and Schneider, 1801) (TL = 22.0 cm), when the average seawater temperature was 28.5 degrees C. The parasitic infection rate was higher in females (11.6%) than in males (4.6%) but there was no relationship between length of fish and parasitism.