Assessing The Effects Of Climatic Variability And Anthropogenic Activities On The Flat Sardinella (Sardinella Maderensis) Fishery Of Ibeju-Lekki, Lagos

Abstract

This study assessed the effects of climatic variability and anthropogenic activities on the Sardinella maderensis fishery of Ibeju-Lekki, Lagos, Southwest Nigeria. Fish and water samples were collected from six sampling stations, while primary data were obtained from 360 fishers across 30 fishing stations from October 2020 to August 2022. Genetic analysis of the fish samples revealed that the species had 89.38 - 100% similarity to Sardinella maderensis in NCBI. Multiple linear regression shows that variability in climatic indicators such as rainfall, chlorophyll-a, mean sea level, sea surface salinity, and sea surface temperature explained approximately 21.90% of the variance in catch per unit effort (p < .001, R2 = .22). Similarly, anthropogenic variables as land use, social amenities, and fishing effort explained approximately 4.62% of the variance in the fish catch (p < .001, R2 = .05). Although the condition factor indicated fish is still in relatively good condition, the result revealed a decrease in the average size (SL) of Sardinella maderensis (from 32cm to 23.2cm). Water samples indicated heavy metals’ levels were above international limits, presence of high total petroleum hydrocarbon (TPH) pollution in all stations (27.56 mg/L- 3985.40 mg/L), TDS levels were higher than acceptable limits (Mean = 24971.1 mg/L) and inadequate chlorophyll-a level (Mean = 0.01 μg/L). The ARIMA model corroborated the results with fluctuating trends in rainfall, temperature, and rising sea levels. It also has a declining chlorophyll-a and fish catch trend. Hence the need for urgent management intervention through coastal management policies and Marine Spatial Planning (MSP) of the Sardinella maderensis fishery.