Determination of mercury in fish fins as a non-lethal assessment method for predicting mercury levels in fish muscle tissues of two species of freshwater fish from three different aquatic environments in Ghana
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Date
September, 2015
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Abstract
Mercury concentration in various tissues (dorsal fin, caudal fin, pectoral fin, pelvic fin and
anal fin) of two species of fish, tilapia (Oreochromis niloticus) and mudfish (Clarias
gariepinus) from three fresh water bodies in Ghana were assessed in order to determine any
relationship between them. Fifteen samples each of the two species were collected from Tono
Dam at Navrongo, Hydroelectric reservoir at Kpong and White Volta at Yapei.
The fish tissues were digested and analyzed by cold vapour atomic absorption
spectrophotometry using an Automatic Mercury Analyzer ( Model HG-5000). For all fish
tissues in all species, Hg concentrations were greatest in muscle tissue (mean muscle Hg =
0.236–0.680 µg/g wet weight), followed by fin tissues (0.03–0.09 mg/kg dry weight). The
coefficient of determination (r
2
) derived from regression analysis of species muscle Hg against
fin Hg ranged between 0.349–0.823 and 0.278-0.752 for tilapia and mudfish samples from
Navrongo, 0.492-0.715 and 0.14–0.37 and 0.737-0.965 for tilapia and mudfish samples
respectively from Kpong and 0.413-0.893 and 0.546-0.960 for tilapia and mudfish samples
from Yapei, respectively. The examination of fin tissues as predictors of muscle Hg resulted
in caudal fin being the better predictor of mercury concentration in muscle of Tilapia fishes
from all three location. The results for mudfish samples also indicated same. It is also
noteworthy that the sensitivity of these nonlethal techniques was highly variable across species
and dependent on specific life history characteristics of the fishes.
The mercury level in the muscle tissues were all within the WHO limit of 5.0 µg/l and hence
poses no health risk to consumers. The mercury concentration in the muscle tissues of 98% of
the fishes in this research recorded results lower than the WHO limit of 0.5µg/g which implies
that consumption of these fishes does not pose any threat to human health
Description
A thesis submitted to the Department of Chemistry, Faculty of Physical Sciences, College of Science, Kwame Nkrumah University of Science & Technology, Kumasi in partial fulfillment of the requirements for the degree of Master of Philosophy (Analytical/ Environmental Chemistry)
, 2015