Heavy metals are non-biodegradable substances which cause serious carcinogenic effects on animals and humans. As fish occupy top position of aquatic food chain, it is a major source of heavy metal contamination. The concentration of Cd, Cr, Pb, Mn, Fe, Cu, and Zn were 0. 0156 -0.1428, 0.163 -8.53, 0.0924 -0.4026, 9.38 -65.9382, 0.0473 -0.1981 and 0.1473 -1.8148 ppm respectively for the fish samples of Cox's Bazar region while 0.0191 -0.1386, 0.8445 -0.1743, 0.102 -0.4625, 0.102 -0.4675, 9.7269 -60.5267, 0.3108 -0.046 ppm for the fish samples of Saint Martin's region. Comparatively high concentrations of heavy metals were found to be accumulated in Mola (Amblypharyngodon mola), Rupchanda (Stromateus chinensis) and Chhuri (Trichiurus lepturus). The order of heavy metal concentrations were Fe > Zn > Cr > Cu > Mn > Cd. The concentration of heavy metals varied from species to species and most of the metals were not significantly correlated, even some metals showed negative correlation among them. Concentration of Fe in some fishes (Mola, Rupchanda and Chhuri) was found higher than WHO guideline values, while other metals exhibited the value below the WHO standard. The results of this study will assist in acquiring information about the level of toxic metals in these regions and to improve the coastal management in these areas in future.
An experiment was conducted with Labeo bata fry for 60 days to examine the growth performance and survival in response to three supplementary feeds i.e. wheat bran, maize bran and mixed diet. The length gain, percent length gain, weight gain, percent weight gain and specific growth of the fry were found significantly higher (p<0.05) in mixed diet. The highest survival rate (74.38±8.1%) was shown by the mixed diet treated fry which was significantly higher than those of maize bran and wheat bran treated fry respectively. There were no significant differences (p<0.05) among the treatments in term of water temperatures, pH and dissolved oxygen (DO). Thus, on the basis of the fry growth performance and survival rate, it could be suggested that the mixed diet of wheat bran and maize bran is suitable for the culture of L. bata fry.Jahangirnagar University J. Biol. Sci. 7(1): 15-21, 2018 (June)
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