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Assessment of Heavy‐Metal Profile of the New Calabar River and Its Impact on Juvenile Clarias gariepinus
Author(s) -
Wegwu Matthew O.,
Akaninwor Joyce O.
Publication year - 2006
Publication title -
chemistry and biodiversity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.427
H-Index - 70
eISSN - 1612-1880
pISSN - 1612-1872
DOI - 10.1002/cbdv.200690010
Subject(s) - clarias gariepinus , catfish , trace metal , environmental chemistry , chemistry , fish <actinopterygii> , dilution , juvenile , heavy metals , metal , fishery , zoology , environmental science , ecology , biology , physics , organic chemistry , thermodynamics
We have determined the heavy‐metal status of the lower reaches of the New Calabar River in the Niger Delta region over a 40‐km‐long distance, and its impact on the development of catfish (juvenile Clarias gariepinus ). The total mean concentrations of dissolved trace metals in the river were 0.01, 0.85, 0.56, 2.08, 0.05, 12.0, and 6.59 mg/l for Hg, Pb, Cd, Cu, Cr, Fe, and Zn, respectively. The accumulated concentration of trace metals in the muscles of different mature fish caught from the river were examined, and the results fell within the action levels adopted in most countries. To evaluate the contributions of trace metals to fisheries depletion, eggs of C. gariepinus were hatched in dilution water spiked with the total mean metal levels determined in the river water. Our results indicate substantive inhibition of egg hatch even at very low concentrations of the majority of the trace metals studied, with mortality rates well above 50% after 216 h of exposure ( Table 5 ). These findings suggest that trace metals (except for Zn), even at very low concentrations, negatively affect fish hatch and fry rearing, implying that aquatic milieus contaminated by trace metals are not suitable as nursery grounds for fish cultures.