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The study has been carried to find out the distribution of different parasites in Exotic carps with respect to different months and seasons. These were isolated and identified from the fishes sampled randomly from five fish markets, which were representing South 24 parganas district, West Bengal. During the study period ten different types of parasites were observed such as Trichodina sp, Chilodonella sp, Trichinella sp., Acanthocephala sp, Nematodes, Epistylis sp, Zoothamnium sp, Vorticella sp, developmental stages of eggs or parasites and some parasites (unidentified) among which most of the parasites were protozoan. Among all the parasites the most dominant were Trichodina sp, Chilodonella sp and Nematodes. Winter was the most vulnerable period to get parasitic infestation. During this period the water quality get deteriorated and the fishes were in stressed condition which favours the parasites to infest. Some parasites were found more during summer which favours their reproduction due to the availability of their intermediate host. In monsoon the temperature fluctuates which also favours growth of some parasites. During the study period Trichinella sp were found solely in Cyprinus carpio exclusively in winter.The protozoan parasites were most available during winter and these were the dominant parasites in exotic carps. These parasites were found mostly on gills and skin of the fishes where as nematodes were found in the intestine and body cavity of the fishes.

The work was conducted to isolate and identify different parasites from Labeo rohita, severity of infestation and to find out Parasitic Frequency Index (PFI, %) monthly, seasons and length wise from different selected districts of West Bengal, India. An investigation was made on Rohu (Labeo rohita), such way that the selected districts were had more potential fishery resources, easy to collect samples from those districts and easy transportation of collected samples to laboratory. Approximately 325 fishes were observed in between April 2012 to March 2013. The infested fishes suffered mainly from respiratory problems, blackness of the skin and mortalities. The present study revealed that the parasitic infestations were found to be the major problem in cultivable fish ponds of West Bengal. In the present study, the isolated parasites were Myxobolus sp., Thelohanellus sp., Trichodina sp., Dactylogyrus sp., Gyrodactylus sp., Nematodes, Argulus sp., Lernea sp., Chilodonella sp., Costia sp., Ichthyoptherius multifilus, development stages and unidentified Crustaceans. Severity of (infestation) all parasites were found to be more. We were found that Myxobolus sp. Thelohanellus sp., prevalence were highest in winter (72% and 56% respectively). Dactylogyrus sp. and Gyrodactylus sp. were more in rainy season and spring respectively (72% and 38% respectively). Chilodonella sp., Costia sp. and Ichthyoptherius multifilus were found high prevalence in spring season. 1 cm to 30 cm length group fishes were more infested with the parasites compare to 30.5 cm to 50 cm length groups.

Article Info ry February Marc h Myxobolussp. 28.33 b 16.66 b 26.66 b 31.66 c 35 c 25 c 33.33 c 55 c 33.33 c 25 b 31.66 c 20 b

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Fish nutrition has advanced dramatically in recent years with the development of new balanced commercial diets that promote best fish growth and health. Feed accounts for a major part (30-70%) of the total operation cost of an average fish farm. Traditionally, animal protein sources, particularly fishmeal have been the major ingredient of aqua feeds. Fishmeal is one of the most expensive ingredients in formulated fish feeds. Due to increasing demand, decreasing supply and the high cost of fish meal, fish nutritionists have concentrated their efforts to find alternative protein sources to substitute fish meal in the diet of fish. Thus, cottonseed meal (CSM), a by-product of the cotton fiber and cottonseed oil industries, may be used to replace fish meal partially or totally in fish diets. However, the cottonseed meal was evaluated by its anti-nutritional factors and its impact on the growth, survival, carcass composition and histopathology of fishes. It is observed that the more research is concentrated on the gossypol content in the cottonseed meal which is described as the antinutritional factor that shows high impact on the growth, carcass composition and pathological changes in the fish. Hence, considering these problems it is advised to use low levels of cottonseed meal in the aqua feeds. The gossypol level can be minimized by the solvent extracted cottonseed meal and be counteracted by the fortification of lysine and adding up of required iron levels. Further research may be required in histopathological studies to assess the toxicity levels in the tissues of the fish due to the gossypol factor.

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