Heavy metals show a wide range of effect on fishes, out of which arsenic (As) and lead (Pb) are among the leading heavy metal toxicants. These heavy metals are known to alter different biochemical parameters, including glycogen level, in different tissues of fishes. Glycogen level in fish serves as the main source of energy; hence, in this study, the acute toxicity test of As and Pb and their effect on the glycogen content and the enzymes involved therein (glycogen phosphorylase, glycogen synthase, hexokinase, phosphofructokinase and pyruvate kinase) were studied in the liver and muscle tissues of Heteropneustes fossilis. The 96 h LC 50 values of As 2 O 3 and PbCl 2 on H. fossilis were found to be 35.09 ppm and 66.20 ppm, respectively. On acute exposure to 96 h LC 50 values of As 2 O 3 and PbCl 2 , the glycogen concentration showed a gradual decrease in both liver and muscle tissues of H. fossilis. However, on chronic exposure (LC 50 /20th ppm), the glycogen content in liver and muscle of H. fossilis was depleted till 20 days; whereas after 30 days, the glycogen level was recovered in both the tissues. The activities of glycogen metabolic enzymes (glycogen phosphorylase and glycogen synthase) and few selected glycolytic enzymes (hexokinase, phosphofructokinase and pyruvate kinase) were also altered in H. fossilis when exposed to acute and chronic concentration of As 2 O 3 and PbCl 2 . Our present results showed that As and Pb induced toxicity stress on the catfish, H. fossilis, which might have caused to alter the carbohydrate metabolism in the fish.

The length–weight relationships (LWRs) of four indigenous fish species; namely Parambassis baculis (Hamilton, 1822); Pethia gelius (Hamilton, 1822); Channa stewartii (Playfair, 1867); and Leiodon cutcutia (Hamilton, 1822) collected from the Ranganadi River in Assam, and the Simsang and Kynshi River in Meghalaya are presented in the present study. The value of the parameter b recorded for P. baculis = 3.347; P. gelius = 3.924; C. stewartii = 2.979; and L. cutcutia = 3.205, with regression coefficients (r2) of 0.993, 0.963, 0.983 and 0.955, respectively. Parameter a was 0.0124 for P. baculis, 0.0037 for P. gelius, 0.0098 for C. stewartii and 0.0273 for L. cutcutia. As information on the LWRs of these fish species is not available in the FishBase database, it should assist future researchers to better analyse the stock of these fishes.