Waidi Abdul

This study assessed the growth and mortality parameters of four commercial fish species (Chrysichthys ni-grodigitatus (Lacepède, 1803), Coptodon zillii (Gervais, 1848), Ethmalosa fimbriata (Bowdich, 1825) and Elops lacerta (Valenciennes, 1847) from Lekki Lagoon, Nigeria. Fish specimens were collected monthly from five landing sites (Wharf, Agbalegiyo, Ebute-Oni, Ilumofin and Luboye). Specimens were collected us-ing proportional sampling based on the level of fishing activities between January and December, 2022. Es-timation of growth parameters was performed according to the growth equation: Lt = L∞- (1- e-K(t-to)) by von Bertalanffy with the Length Frequency Data Analysis (LFDA) package. The length-converted catch curve model was adopted for the estimation of mortality parameters using FiSAT II software. Results showed that C. nigrodigitatus exhibited the highest growth rate (K = 1.30 yr⁻¹) and exploitation rate (E = 0.83) with an as-ymptotic length (L∞) of 53.94 cm. However, C. zillii exhibits the lowest growth curvature (K = 0.44 yr⁻¹) with L∞ = 39.15 cm and an exploitation rate of 0.42. E. fimbriata showed a rapid growth rate (K = 1.15 yr⁻¹) but low exploitation (E = 0.12), while E. lacerta exhibited moderate growth rate (K = 0.58 yr⁻¹) and low exploita-tion (E = 0.16). It is concluded that C. nigrodigitatus is overfished in the lagoon, which demands a closed season and small mesh size restriction to prevent recruitment overfishing. The low exploitation levels of E. fimbriata and E. lacerta means that these stocks are currently sustainable, but there is a need to monitor them to avoid future over-exploitation.

In this study the accumulation of Iron (Fe), Zinc (Zn), Cobalt (Co), Chromium (Cr), Cadmium (Cd), Lead (Pb) and Nickel (Ni) in sediment, water, some fish samples (Schilbe mystus, Mormyrus rume, Gymnarchus niloticus, Cynoglossus senegalensis, and Chrysichthys nigrodigitatus) and an aquatic plant Eichhornea crassipes collected from Lekki lagoon, Lagos Nigeria were examined. Heavy metals in the water, sediment, some selected fish and an aquatic plant were determined seasonally across nine sampling Stations; in the gills, liver and muscles of the fish species and in the root stem and leaves of Eichhornea crassipes using an atomic absorption spectrometer (AAS). Heavy metals concentrations in the sediment and water varied significantly, both spatially and seasonally. Metal concentrations varied between species and body parts while Co, Cr and Pb were not detected. Ni was found in the liver and gills of S. mystus and M. rume and Cr in the gills of G. niloticus only. In Eichhornea crassipes, metals detected were in the order: root>leaves>stem for Fe, Zn, Cr, and Cd; root>stem>leaves for Pb and Ni while Co was not detected. Heavy metal presence in Lekki Lagoon calls for monitoring of activities within and around the lagoon and policy development towards the sustainable ecosystem health services. Keywords: Pollutants, Heavy metals, Eichhornia crassipes, Bioaccumulation, Lekki lagoon