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The present study was carried out from July 2005 to June 2007 and diseased freshwater fishes were collected from different water bodies and fish landing centre of three study areas, namely City Corporation area, Rajshahi; Paba upazila and Charghat upazila, Rajshahi. In the present study the load of bacteria in lesion, liver and kidney of H. molitrix showed considerable variation in different months during the study period. Monthly variation of bacterial load in body lesion varied from 3.17×104 CFU/g (July’05) to 2.13×107 CFU/g (March’07), in liver it varied from 7.17×103 CFU/g (July’05) to 5.13×106 CFU/g (March’06) and in kidney it varied from 5.87×103 CFU/g (July’05) to 6.33×105 CFU/g (March’06). From two years observation, monthly variation of bacterial load in 3 sampling ponds were varied from 4.00×106 CFU/ml (June’07) to 3.93×107 CFU/ml (July’05) in case of pond-1. In pond-2 bacterial load varied from 1.27×106 CFU/ml (May’07) to 5.33×107 CFU/ml (September’06). In pond-3 the bacterial load varied from 2.10×106 CFU/ml (June’07) to 2.10×108 CFU/ml (July’06). DOI: http://dx.doi.org/10.3329/jsf.v9i1-2.14650 J. Sci. Foundation, 9(1&2): 77-84, June-December 2011

Abstract:The research work was conducted to measure the nursery pond water quality parameters during the period of June 2006 to May 2007 in Mymensingh. The highest value of water temperature, alkalinity, ammonia, free carbon dioxide, DO, P H and hardness was 30.2 0 C (May'07) in pond-1, 174ppm (Feb.'07) in pond-2, 3.5ppm(July'06) in pond-1, 8.5ppm (Dec.'06&Jan.'07) in pond-1, 9ppm (July;06) in pond-1(also in April in pond-2), 8.4 (June'06) in pond-2 and 175ppm (Sep.'06) in pond-2 respectively. The lowest value of these parameters was 18 0 C (Jan.'07) in pond-2, 70ppm (Nov.'06) in pond-1, 0.03ppm (Sep.'06) in pond-2, 4ppm (Sep.'06) in pond-2, 5.5ppm (June'06) in pond-1, 6.2 (Oct.'06) in pond-2 and 64ppm (March'07) in pond-1. The value of physicochemical parameters of water had more or less significant combined effect on one another.

The impact of a fish sanctuary on fisheries diversity was studied for two years in Chalan Beel, Tarash Upazila, Sirajganj district, where the sanctuary was established at the end of the first year. Seine net (Berjal) was used to collect data on a monthly basis. There were 42 species recorded from 8 orders and 18 families, including two exotic species, Cyprinus carpiro and Oreochromis mossambicus. Puntius puntio was the most common species (18.38%), followed by Colisa fasciata (9.73%) and Chanda nama (9.28%). The order Cypriniformes (16 species) was discovered to be the dominant order, accounting for 47.78% of the total order, followed by Perciformes (22.85%) and Siluriformes (21.40%). The Shannon-Weaver diversity index (H) ranged between 2.26 and 2.66. The average value was higher (2.53) after the sanctuary was established than before (2.39). The impact of the fish sanctuary may have resulted in an increase in the biodiversity index and total catch. As a result, sanctuary establishment can be expanded to address the gradual improvement of fisheries diversity. J Bio-Sci. 30(1): 61-68, 2022 (June)