ABSTRACT
Heavy metal pollution in aquatic environments is particularly concerning due to its detrimental effects on aquatic fauna and human health. Fish, as key members of aquatic ecosystems, accumulate heavy metals, and are thus good bioindicators of heavy metal pollution. The monitoring of heavy metals in fish has typically relied on invasive methods that involved sacrificing the fish for tissue sampling, while this may be effective, these invasive techniques may not be sustainable because of the large number of fish sacrificed. There is therefore a growing interest in non-invasive methods that allow for the assessment of heavy metal pollution without harming the fish. This study aimed to evaluate the efficacy of non-invasive methods, specifically fish scales and caudal fin clips, in assessing heavy metal concentrations in two scaly fish species, Brycinus macrolepidotus and Oreochromis niloticus, from Ikpoba River in Edo State, Nigeria. Fish tissues, including muscle, scales, and caudal fin clips, were digested using standard procedures, and heavy metal concentrations were determined using Atomic Absorption Spectrophotometry. Results indicated higher heavy metal content in the muscle tissue of Brycinus macrolepidotus and the caudal fin clips of Oreochromis niloticus, with iron being the most prevalent metal detected in both species. Lead concentrations were below detection levels in both species. Fins had significantly higher heavy metal contents(p<0.05) compared to muscle and scale tissues in Oreochromis niloticus, while significant positive correlations (p < 0.01) of heavy metals between muscle, scales and caudal fin clips was observed in B. macrolepidotus indicating that the use of scales and caudal fin clips of B. macrolepidotus and fins for O. niloticus could be better non-invasive alternatives for the assessment of heavy metals in these fish species. The study concludes that non-invasive assessment methods can effectively determine heavy metal concentrations without harming these fishes, promoting biodiversity conservation and species diversity. Non-invasive methods provided results comparable to invasive techniques, highlighting their potential for widespread use for the determination of heavy metal concentrations in fish populations.
