Fertility, survival rate and hatching rate of hybrids of local magur Clarias batrachus and African cat®sh C. gariepinus were compared with the purebred species.

An experiment was carried out to determine the comparative growth study of Vietnam koi (Anabus testudineus) and Thai koi (Anabus testudineus) for a period of 90 days in eight experimental ponds in the northern side of the Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh. Four treatments were considered having two replicates. For Vietnam koi treatments were named VT 1 and VT 2 and for Thai koi were TT 1 and TT 2 . All the fish were of same age group having mean body weight of 0.30 g. Feeding frequency in all the treatments were two times a day. Fish were fed quality fish feed at a rate of 60% of their body weight for the first thirty days that was gradually reduced to 25% for the next thirty days and 10% till the termination of the experiment. The mean value of water temperature were 29.78 in VT 1 , 30.42 in VT 2 , 30.50 in TT 1 and 29.99°C in TT 2 , dissolved oxygen were 7.21, 7.42 , 7.14 and 7.34 mg/l in VT 1 , VT 2 , TT 1 and TT 2, respectively, mean pH values were 7.42 in VT 1 , 7.29 in VT 2 , 7.50 in TT 1 and 7.45 in TT 2 , ammonia were 0.21, 0.24, 0.28 and 0.23 mg/l in VT 1 , VT 2 , TT 1 and TT 2 , respectively and alkalinity were 200.00, 205.00, 210.00 and 205.00 ppm in VT 1 , VT 2 , TT 1 and TT 2 , respectively. The result of the present study showed that the best weight gain of 80.00 g was observed in VT 1 after 90 days of culture period. Average weight gain (g) were 0.83, 0.88, 0.51 and 0.61; SGR (per day) were 3.93, 3.95, 3.65 and 3.71%; FCR were 1.50, 1.67, 1.70 and 1.90; survival rate were 78.50, 76.50, 90.00 and 82.00% and fish production were 7,839, 15,923, 5,519 and 11,820 kg/ha/3 months in VT 1 , VT 2 , TT 1 and TT 2 , respectively. Growth of both the species was higher in lower stocking densities, whereas, production was increased in higher stocking densities. The present research findings suggested that Vietnam koi has high growth potential in comparison to Thai koi under mini pond culture condition.

Clinical and histopathological studies were carried out with juvenile common carp (C. carpio) from a Government fish farm and a NGO fish farm in Mymensingh area for a period of 9 months from April 2005 to December 2005. Clinically red spots, scale loss, weak body, hemorrhage and subcutaneous lesion were noticed especially during November and December. A moderate pathological change in the investigated organs of all fishes were recorded in summer season (April-May), whereas in rainy season (June-July) pathological symptoms were significantly reduced which was again increased to some extent in the autumn season (August-September). However, marked pathological changes such as necrosis, protozoan cyst, bacterial colony, vacuum, melanomacrophase, hemorrhage, hypertrophy, hyperplasia and clubbing were recorded in all the investigated organs like skin, muscle, gill, liver and kidney in the months of October, November and December. Among the affected organs gills were more affected with the presence of numerous protozoan cysts followed by skin, liver and the less affected organ was the muscle. Clinically and histopathologically juvenile common carp of Government fish farm were more affected compare to NGO fish farm especially in colder moths of the year.

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An experiment was conducted for a period of 28 days to observe the effect of plant extracts on recovery of fish diseases. The experiment was carried out in mini pond (1.75 decimal) behind the Fisheries Faculty in BAU, Mymensingh. Twelve hapas (3 ×2 ×1.5 sq.ft.) and five studies were conducted with control hapa with 3 treatments and two replicates each. Four medicinal plant products were collected and prepared. In study 1 fishes were treated with Neem Seed Oil, study 2 with Kalojira Seed Oil, study 3 with Neem Leaf Extract, study 4 with Mahogoni Seed Oil and the control hapa was provided with normal feed. The treatments were practiced as 2ml, 4ml and 6ml per kg feed. At the beginning of the experiment, fishes had red spots on dorsal and caudal region, scale missing, large abrasions and black to grayish spots. In Kalojira Seed Oil (study 2) treated fish, spots and lesions were totally recovered in T2 and T3 whereas in T1 there were traces spots at the end of the experiment. However, in Neem Seed Oil and Neem Leaf fine extract treated fish (study 1 and study 3), injury, abrasions and lesions were almost healed up in T3 (6ml/kg feed) and moderate recovery in T2 and T1. In Mahogoni Seed Oil (study 4) treated fish, ulcers and lesions were reduced in size but existed distinctly in all the treatments at the end of the experiment. In control study (study 5) injury and abrasions had no recovery but remained almost similar till the end of experiment. Thus it was found that Kalojira Seed Oil performed best recovery (90-95%) followed by Neem Seed Oil (78-84%), Neem Leaf fine extract (70-75%) and poor performance was observed with Mahogoni Seed Oil extract (35-40%). So, kalojira seed oil was the best performed herb and T3 (6ml/kg feed) was the best dose followed by T1 and T2.