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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.

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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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The present study was carried out for a period of 42 days to find out the effect of different acclimation salinities (0-control, 2, 4, 6 and 8 ppt) on the haematology of Labeo rohita fingerlings. The fish remained active and showed normal feeding and swimming behaviour up to 4 ppt salinity level; however, at 6 and 8 ppt, they get stressed but were able to survive. There was no significant difference in haematological parameters among fishes in the control, 2 and 4 ppt treatments. Haematocrit (Ht%) values were within the optimum range at 0, 2 and 4 ppt salinity. The mean haematocrit values ranged from 22.21 (at 8 ppt) to 27.03 (control). The highest mean haemoglobin content was observed at 0 ppt (7.09 g dl-1) and it was lowest at 8 ppt salinity (5.36 mg dl-1) on the day of termination of the experiment. Mean total erythrocyte count (TEC) was highest (1.83x10 6 mm-3) at 2 ppt salinity and the lowest was at 8 ppt salinity (1.52 x10 6 mm-3). The mean total leukocyte count (TLC) was highest at 8 ppt (4.81x10 3 mm-3) and the lowest value was recorded at 0 ppt (4.35 x10 3 mm-3). The mean plasma glucose level at 8 ppt (62.43 mg dl-1) was the highest among the different groups and lowest of 44.70 mg dl-1 was seen in control fishes. Results of the study indicated that increasing salinity up to a certain level is tolerated by L. rohita through osmoregulation, however, extreme salinity stress can lead to alterations in the haematology as well as physiology and further the inability to adapt, leads to metabolic downregulation, thereby affecting growth.