This study reports the curative effects of zinc and ascorbic acid on cadmium induced histopathological changes in kidney of the freshwater cat fish Heteropneustes fossilis. Exposure of the fish to 16.14 mg/L sub lethal concentration of cadmium for 30 days induced hypertrophy of glomeruli, dilation and rupture of Bowman’s capsule and glomerular tuft, degeneration of epithelial cells lining the renal tubules, haemorrhage between tubules, hyaline degeneration of tubules, indistinct lumen, cytoplasmic vacuolation, accumulation of lipid droplets and generalized necrosis in kidney. However, 16.14 mg/L cadmium + 0.5 mg/L zinc and 16.14 mg/L cadmium + 1.25 mg/L ascorbic acid exposed fish groups revealed signs of recovery which were more progressive with ascorbic acid as evident from considerable restoration of normal size of Bowman’s capsule, structure of tubular epithelial cells and almost normal structure of renal corpuscles. Our study concludes that zinc and ascorbic acid have protective influence on cadmium toxicity in fish but higher doses than the one selected in the present case are probably needed to overcome the effects of cadmium toxicity.

The scientific explanation for shrinking of water body could be the change in climate. The present trend of global warming speeds up shrinkage of water area over the land, especially the reservoirs and lakes. The environment of it undergoes certain changes which have brought degradation as direct impact on the inhabitants and their economic activities. Many aquatic bodies of the world are facing the threat of shrinkage.

The present study attempts to explore the evidences that prove increase of temperature in Ranchi district (Jharkhand) during the last decades and degradation of aquatic environment with changes of its area covered.

Studies on cyclic changes (for 12 months) in aquatic, aerial and total oxygen uptake in a fresh water air breathing fish, Channa marulius (Ham.) were made which showed wide range of variations in different months of the year. It ranged from a minimum value of 0.838, 0.283 and 1.121 m102/h in December to a maximum value of 2.888, 2.363 and 5.251 m102/h respectively in the month of June. Statistically significant correlation was observed between seasonal variations in oxygen uptake and seasonal changes in ambient water temperature but the points on a plot gave good fit to two regression lines, inflection at the meeting point of the two regression line was observed at 29.20C in this fish. The details have been discussed in this paper.

In the present work an attempt has been made to study oxygen consumption in different weight groups of a teleostean fish, Puntius sophore (Ham.) at habitual water temperature in winter and summer months to assess compensatory regulation in their metabolism to seasonal thermal variations. The experiments were conducted at 19.0±1.00C (winter) and 29.2±1.00C (summer months). Though at both the habitual temperatures, a clear trend of increase in total oxygen consumption with increasing body weight was observed but it increased with a value of 0.64 (b value or regression coefficient) in summer months while such value was recorded to be 0.80 (b value) in winter months indicating compensatory regulation in their metabolism to seasonal thermal variations. The details have been discussed in this paper.

The acute and sublethal toxicity of Nuvan (Dichlorvos 76% E.C. – an organophosphate pesticide) on a commercial freshwater air breathing climbing perch, Anabas testudineus (Bloch) was evaluated under static bio-assay condition for 24, 48, 72 and 96 hrs. The LC„ (TLm) values were computed to be 30.65, 27.85, 23.70 and 18.50 ppm at water temperature 29.0±1.0°C. The safe concentration value was calculated to be 6.90 ppm at this temperature. The behavioural response of fish towards the toxicant (Nuvan) was grossly dependent on concentration and length of exposure. The mean values of opercular movements (per minute) gradually decreased with the increasing concentration of Nuvan. The reason for such changes have been discussed in the present paper.

Studies of metabolic rate (bimodal oxygen uptake) have been studied in an air breathing fresh water fish, Channa marulius (Ham.). Aquatic, aerial and total oxygen uptake per unit time (m102/h) in Channa marulius ranged from 0.963 to 5.213, 0.666 to 3.313 and 1.623 to 8.526 respectively within the weight range 9.52 to 95.0g. Statistical analysis of the data reveals that with unit increased in body weight, aquatic, aerial and total oxygen uptake in this fish increased by a fractional power of 0.8309, 0.7229 and 0.7737 respectively. Aquatic, aerial and total 02 uptake per unit body weight (cc/kg/b) decreased by a fractional power of -0.1910, -0.2796 and -0.2302 respectively. The percentage of aquatic : aerial oxygen uptake in this fish were 60.62: 40.38. The details have been discussed in this paper.

In the present work an attempt has been made to evaluate the toxic effect of Furadan (a carbamate pesticide) on histopathological and histochemical changes in the stomach of a fresh water mud eel, Macrognathus aculeatus (Bloch) at sublethal concentrations (0.6, 0.80 and 0.90 ppm) for 10 and 20 days expsoures. Such treatment caused reduction in the columnar epithelial cells and mucosal folds became stumphy and widened; after 20 days intoxication mucosal fold and submucosa got damaged; tunica propria and musculature also got damaged. With the use of certain stains such as PAS, Bromophenol blue and Best Carmine etc. changes in the intensity of stains for carbohydrate, protein and glycogen test have been studied in control and intoxicated fishes. The details have been discussed in this paper.