The study of prevalence and mean intensity of endoparasite (digenea) on thunnus obesus (bigeye tuna) from South China Sea

Abstract

Digenean parasite is one of the parasites that affect marine fishes which cause the fish to be lower in quality and unappealing to eat if the number of parasites is high. Study the parasites on fish can contribute to many aspect includes aquatic pollutants and the migration of fish itself. However, the study on digenea from Tuna in Malaysia is rare. So that I choose this project because tuna is one of fisheries sources in our country. In this study, the prevalence and mean intensity of digenea in bigeye tuna become major aspects. 32 Thunnus obesus obtained from South China Sea was dissected to examine digenean parasite from their internal organ. The heart, lymph, pyloric caeca, stomach and intestine was examined under dissecting and compound microscope. All the digenean found was collected and preserved in 70% alcohol in the bijou bottle. The digenea then was stained and drawn under a camera lucida attached to a compound microscope in order to identify the taxonomy of those digenea. The identification was referred to a book written by Yamaguti (1958). The end result shows that 20 Thunnus obesus was infected by 2 different digenean parasites known as Tetrochetus sp. and Rhipidocotyle sp. The prevalence and mean intensity of these digeneans was 62.50% and 6.5 respectively.