Assessing climate change driven variations in pelagic fish species distribution and abundance in the North East Atlantic fishery of Sierra Leone

Mr Sheku Sei1, Mr Ciaren O’Donell2, Mr Abdoulaye  Sarre3

1Ministry of Fisheries and Marine Resources, Freetown, Sierra Leone, 2The Marine Institute, Ornamore, Ireland, 3Senegalese Institute of Agricultural Research, Dakar, Senegal


Coastal Sierra Leone is among the West African countries with high vulnerability to climate change. Recent increases and shifts in climatic regime continues to negatively impact important fishery resources.  An analysis of temperature distribution and fish abundance, using hydrographic and acoustic surveys in three consecutive cruises have revealed direct relationships between temperature increases and reductions in pelagic fish abundances. The spatial distribution of commercially important pelagic fish resources of the clupeids (mainly sardinella, bonga shad and anchovy) and the carangids (mainly horse mackerels and the jacks) relative to temperature variations along 40 hydro-acoustic trawl stations suggests marked decreases in fish abundances as surface temperatures increase. Consistent fluctuations of sea surface temperature and variations in fish abundance were pronounced in the southern shelf around Sherbro Island of the Southern Coast. The study further shows that within the shallow zone of a major fishing ground of Banana Island, a warm mixed water mass of temperatures around 31°C occupied up to 10m from the surface, with conventional forcing and mixing in carangid fish communities. The presence of a 25°C isotherm at deeper layers of 20m coincided with nearshore and offshore salinity increases and decreasing pelagic fish abundance. These temperature variations are critical for the sustainability of the Sardinella and Horse Mackerel fish species, which are already fully exploited and listed on the IUCN red list of threatened species. Our study confirms that wind induced mixing creates isothermal temperatures and sea surface warming, which accounts for alterations in fish aggregations and abundance.


Acting Assistant Director of Research and Policy at the Ministry of Fisheries and Marine Resources in Sierra Leone for over 15 years. Natural Resource Management Expert at the Natural Resources Management Consortium (NaReMaC)  in Sierra Leone.

Conducts fisheries research, socio-economic and policy analysis for marine resources. Design and management of marine protected areas  including climate change vulnerability assessment. Part-time Lecturer in aquatic resource economics and National Expert in fisheries abundance surveys. Delivery of consultancy services for the development of fisheries management plans including the introduction of territorial use right fisheries and quota management systems. Provision of long term policy support for fisheries management including the design of fisheries and aquaculture policy and legal reforms to promote food security. Coordinate the effective delivery of Sierra Leone fisheries contributions to the NEPAD Agency’s Comprehensive Agricultural Development Program(CAADP) objectives, to increase benefits from Africa fisheries and promote regional economic integration through debates on regional fisheries policy reforms.

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