Inter-specific hybridization between freshwater catfish Mystus cavasius (Ham & Buch) and M. seenghala (Sykes) by artificial fertilization.

By employing the technique of induced ovulation for artificial fertilization, inter-specific hybrids between the threatened catfish species (Mystus cavasius x M. seenghala) were produced. Fertilization, hatching and survival were significantly different between control and hybrids. The hatching time of the hybrid was significantly lower than that of the control. The average performance viz., hatching time and viability of larvae of the control fish, was significantly better than that of the hybrids. In the hybrid cross, hatchlings were mostly deformed and abnormal and after yolk absorption ultimately succumbed.

Effect of formulated diet on digestive enzymes of Labeo rohita (Ham.).

Six sets of feeding experiments were carried out using formulated diets containing prawn head waste (PW), chicken intestine waste (CW), banana flower (BF), cauliflower waste (CAU) Dolicos lab lab (DLL) and groundnut leaf (GNL) in four levels of inclusion (15, 30, 45 and 60%) to assess the pattern of distribution and activities of digestive enzymes like cellulase, amylase, maltase, invertase, protease and lipase in the digestive tracts of Labeo rohita fingerlings. A control group of fish was fed with diets containing antibiotics to destroy the digestive tract microflora which may induce digestive functions. In general, the activity of digestive enzymes depended on the amount and type of the ingredients present in the diets ingested by the fish. Test animals showed both endogenous and bacterial cellulase activities which suggests the necessity for including cellulose (plant protein source) as dietary ingredient. Occurrence of higher amount of cellulase in the foregut and amylase in the fore and midgut influenced by DNL and GNL diets revealed the possibility of including less than 40% of the respective ingredients in the diet of rohu. Maltase and invertase were highly influenced by GNL, DLL and BF diets than PW and CW diets. More than 40% inclusion of PW and CW was found to increase protease and lipase secretion in the midgut and hindgut regions. The higher secretion of lipase in the midgut suggested the physiological versatility for lipid digestion in rohu fingerlings.

Hematological effects of textile mill effluent on freshwater fish Oreochromis mossambicus (Trewaves).

O. mossambicus was exposed to sublethal concentrations of a textile mill effluent to study the hematological changes as a function of feeding/starvation, aeration/non-aeration and concentration. Increase in concentration produced a dose dependent increase in RBCs (0.87 x 10(6) to 1.63 x 10(6)/mm3), WBCs (0.070 x 10(6) to 0.520 x 10(6)/mm3), hemoglobin (3.7 to 5.6%) and hematocrit (9.0 to 12.3%) and a decrease in MCV (111.8 to 88.2 microns 3), MCHC (41.05 to 31.35%) and MCH (44.2 to 33.9 pg).