The Implication of Climate variability on the Depletion of Fish Reserve in the Coastal Water of Southwestern Nigeria

Abstract

This study examines rainfall and temperature trends from 1974 to 2021 across Lagos, Ogun, and Ondo states in Southwest Nigeria, analyzing their implications on fish reserves. The region, characterized by a humid tropical climate with distinct wet and dry seasons, experienced a long-term increase in rainfall at 3.69 mm/year and a mean annual temperature rise of 0.28°C per decade. Long-term climatic data (1974 and 2021) from the Nigerian Meteorological Services (NIMET) for Lagos Island, Ijebu-Ode, and Ondo synoptic stations reveal significant variability in climatic patterns, including four distinct rainfall periods and oscillating temperature trends. Notably, the 1980s emerged as the driest decade in a century, while recent years exhibited increased rainfall and temperature, consistent with global warming trends. Based on the established meteorological and fisheries data and using time series analysis, climate variability impacts aquatic ecosystems affecting fish habitats through altered salinity, flooding-induced eutrophication, and habitat shrinkage during dry spells. The time series analysis show a rising temperatures which will exacerbate thermal stress, metabolic demands, and oxygen depletion, further depleting fish populations. For instance, high rainfall years like 2014 and 2019 caused increased freshwater inflows, disrupting ecosystems, while extended dry periods, such as 2013–2020, reduced river flows and fish habitats. The findings underscore the critical need for adaptive management strategies, including wetland restoration, pollution control, and sustainable fishing practices, to mitigate these effects. Drawing from global examples like the Mekong Delta and the Great Barrier Reef, the study highlights the urgent need for integrated climate resilience measures.