Dissertation (MSc Biodiversity)This study assessed the diversity of parasites of milkfish Chanos chanos cultured along Zanzibar coasts. The study analyzed the prevalence, mean intensity, diversity and richness of parasites species and to relate the occurrence of this parasites in relation to physico- chemical parameters of the ponds water and feeding modes of the fish. Three different localities were selected for this investigation. A total of 110 milkfish were dissected, the body cavity of each fish removed out ventrally and each organ were cut and opened separately and kept in physiological saline, hand lenses and dissecting microscope were used for parasites examination. Out of 110 milkfish examined 59 were infected with endoparasitic worms, the overall prevalence of infection was 53.64% and mean intensity of 3.98. The study found that 33 fish were infected with nematodes Camallanus sp. with prevalence of 30%, 13 fish were infected with Capillaria sp. with prevalence of 11.82%, 23 fish were infected with cestoda Scolex pleuronectis with prevalence of 20.9% while 5 fish were infected with acanthocephalan Cavisoma magnum with prevalence 4.5%. All parasites were observed in body cavity, 92.34% of these parasites were found in intestines and 7.66% found in stomach. Results of Shannon and Wiener Index H' of diversity showed that Donge ponds had high diversity of parasite species compared to Bumbwini pond 0.89 and 0.75 respectively. While Shakani pond recorded the lowest species diversity of 0.68. Bumbwini showed high prevalence of 76.67% and parasites mean intensity of 4.96. Donge had prevalence of 66.67% and mean intensity of 3.6 while Shakani pond show the lowest prevalence of 32% and mean intensity of 3.1. Also the observation of this study revealed that parasitic infection was high with increase fish size. The incidence of parasites did not show relationship with physico - chemical parameters of the ponds water: temperature, pH, Dissolved oxygen, (DO) and salinity of the water since p value is greater than significant value, p > 0.05. However parasite communities varied with different modes of feeding between sites under study. From this finding it is recommended that farmers should be given adequate technical knowledge on suitable fish culture methods and proper husbandry in order to prevent parasitic infection and disease so as to raise healthy fish and to achieve high production of fish stock