The Guinea Current is the dominant feature of the shallow ocean off the coast of countries in Western Africa stretching from Guinea Bissau in the north to Angola in the south. The distinctive bathymetry, Hydrography, productivity and trophodynamics of this shallow ocean quality it as a Large Marine Ecosystem (LME) and is indeed recognised as one (n°28) of the fifty LMEs delineated globally.
The oceanography of the two Congos and Angola further to the south is influenced by the Guinea Current and thus there is ample justification for including the tree countries in the Guinea Current Large Marine Ecosystem (GCLME). The northern subsystem of the GCLME is thermally unstable and is characterised by intensive seasonal upwelling while the southern half, which is generally thermally stable, depends on nutrient input originating from land drainage and river flood and turbulent diffusion, although less intensive and periodic upwellings have been reported. These characteristics combine to make this area as one of the orld's most productive marine areas that is rich in fishery resources, petroleum production, and an important global region of marine biological diversity.Approximately 40% of the region's 280 million people live in coastal areas and are dependent on the lagoons, estuaries, creeks and inshore waters surrounding them. Rivers and lagoons serve as important waterways for the transportation of goods and people. They are also important sources of animal protein in the form of fish and shellfish. Unfortunately, pollution from residential and industrial sources has affected the waters of the GCLME, resulting in habitat degradation, loss of biological diversity and productivity, and degenerating human health (IOC-UNESCO & IAEA Marine Environmental Laboratory).
In the coastal pelagic fishery, economically important species are linked to the availability of phytoplankton and zooplankton. The target species off the Coast, Ghana and Togo are Sardinelia aurita, Sardinelia maderensis, Scomber japonicus and Engraulis encrasicolus. In Ghana, for example, small pelagics contributed 125,000t and 247,000t to the total marine production of 234,000t and 371,000t in 1985 and 1992 representing 54 and 66 percent of the fisheries yield respectively, indicating their importance to food security of the region.
Further south from Benin to Democratic Republic of the Congo, the target species are Ethmalosa fimbriata, Sardinella maderensis, lisha africana. Demersal fisheries, of higher economic value than pelagics, have as their targets croakers, Pseudotolithus elongatus, Psendotholitus senegalensis, Pseudotholitus typus, polymenids, Galeoides decadactylus, polydactylus quadrifilis, grunters, big eye tuna, Brachydeuterus auritus, catfish, Arius sp. Pomadasys sp soles and Cynoglossus sp In the highly lucrative coastal demersal shrimp fishery, the pink shrimp Paenus notialis is dominant but other target species include the Parapenaeopsis atlantical and Penacus kerathurus. Shimpring grounds cover 2,500 mi² off Nigeria, 190 mi² off Cameroon and 180 mi² off Benin.
Exclusively exploited by small scale operators with passive cane or netting grear in the estuaries, and with miniature trawls in the surf zone, white shrimp, Nematopalaemon hastatus a major fishery off Nigeria - Cameroon. Potential is about 150,000t/Year off Nigeria. The shrimp resources of the ecosystem are an important export species.
The rich fishery resources are both locally important resident stocks supporting artisinal fisheries, and transboundary stradding and migratory stocks that have attracted large commercial offshore foreign fishing fleets from European Union, Eastern Europe, Korea and Japan. Since the 1960s, the offshore commercial fishing efforts have exerted extreme pressures on the resources, placing the fisheries at risk of collapse. This is exacerbated by the present of local industrial fleets, predominantly nationally owned or part of joint ventures operating in each others water under bilateral agreements, as the existence of a large artisinal sector with strong traditional roots and powerful social and political impacts. Catch per Unit Effort (CPUE) is exceeding sustainable yields in some countries (Ajaji, 1994, The Status of marine Fishery Resources of the Gulf of Guinea: In: Proc. 10th Session FAO, CECAF, Accra, Ghana, 10-13 October 1994) while species diversity and average body total lengths of the most important ish assemblages have declined. The negative trends of over-exploitation of fish and fisheries from lack of management and adequate forecasting system have economic and food security implications not only for the 280 millions people of the region and the growing food (protein) needs of the region will need to be examined in the context of the substantial extent to which foreign fleets are exploiting the fishery resources of the GCLME.
Mangroves of the GCLME are a particularly important resource for coastal communities. They are used for firewood, fish smoking, building materials, salt production, oysters and fisheries and medicinal purposes. Unfortunately, overuse and, to a lesser extent, pollution has severely damaged the mangroves. Urban expansion and industrial growth has led to mangrove reduction to such an extent that several species once present are no longer found. In many instances mangrove areas have been reduced to saline grasslands of Paspalum vaginalum.
Mangroves, typically Rhizophara sp, Conocarpus sp, Avicennia sp, Mitragyna inermis, Laguncularia ap, occur almost everywhere along the coast in the GCLME and are dominant in certain places such as the Niger Delta of Nigeria where the mangrove swamp forests extend over an area of 9,000 km2 between the region of Benin River in the West and the Calabar-Rio del Rey estuary in the East. Mangrove forest provide the nutritional inputs to adjacent shallow channel and bay systems that constitute the primary habitat of a large number of aquatic species of commercial importance. The importance of mangrove areas as spawning and breeding grounds for many transboundary fish species and shrimps is well known. Beside the rich flora, there is a diverse array of associated fauna including small mammals such as statungas, otters, Atilax paludinosus, Dasymys incomtus and large mammals such as Cephalophus sp. Molluscs found in this habitat include Crassostrea gasar, cams Arca senilis, Volutes Cymbium pepo, cones, cowries and conches. These molluscs form an important basis for fish and bird food chains as well as being a major food humans. Mongroves still harbour at least three species of crocodiles, one known locally as alligator, and the endangered west African manatees Trichechus Senegalensis. Presently the magrove forests are under pressure from over cutting (for fuel wood and construction timber) and from other anthropogenic impacts thereby jeopardising their roles in the regeneration of living resources and as reservoirs of biological diversity.
The physical destruction of coastal habitats including wetlands cause the loss of spawning and breeding grounds for most living resources and the loss of the rich and varied fauna and flora of the region including some rare and endangered species. In Ghana, 55 percent of the mangroves and significant marshlands around the greater Accra area has been decimated through pollution and overcutting. In Benin, the figure is 45 percent in the Lake Nouake area, in Nigeria, 33 percent in the Niger Delta, in Cameroon, 28 percent in the wouri Estuary and in Côte d'Ivoire, about 60 percent in the bay of Cocody.
Agriculture is important to all countries in the region, both at subsistence and commercial level. A number of rural and agriculture practices impact the marine and coastal environment. The use of chemical fertilisers and pesticides has markedly increased with the development of commercial agriculture and the need to improve food production and protest human health against insect-borne diseases. Although organochlorine based pesticides are still used, awareness of their danger has spread so the majority are now organo-phophorous and carbamate based. Run-off of these chemicals may reach surface or groundwater where they may persist for long periods. Investigations of PCBs have shown they exist at a background level but are not a problem yet Inorganic, especially nitrate and phosphate based, fertilisers are being used on an increasing scale. Substantial quantities of nutrients originating from domestic and agricultural effluents which are used in primary production are carried to the sea through river outflows It is estimated that approximately 30% of fertilizer applied are actually utilised by the plants while the reminder finds it way into the atmosphere or into surface waters. These nutrients, when coupled with sewage pollution, are a serious threat to lagoons. (Portmann, J.E, Biney, C., Ibe, C. and Zabi, S. (1989), State of the Marine Environment in the west and Central Africa Region, UNEP Regional Seas Reports and Studies, No. 108.
Nearly all major cities, agricultural plantations harbours, airports, industries as well as other parts of the socio-economic infrastructure in the region are located at or near the coast. This is due in part to the richness of natural resources in the coastal areas of the Gulf of Guinea and partly also as a result of the history of early European contact. The result is that unplanned urbanisation and development, including habitat destruction of coastal areas coupled with the rush to industrialise, exert phenomenal pollution pressures on this international body of water (WACAF Intersecretariat Co-ordination Meeting, Rome, 1993).
The stresses arising as result of these complex and interactive human developments are leading to increases in harmful impacts on the environment and natural resources of the GCLME :
Large-scale changes in the abundance levels of the resident fish stocks near shore and the conditions affecting the sustainability of the stradding (shared) and highly migratory fisheries of the region, both of which have food security and economic implications to the 280,000,000 people of the region;
The physical destruction of coastal habitats including wetlands, mangroves, and the loss of spawning and nursery grounds for living resources and the loss of the rich and varied fauna and flora of the region including some rare and endangered species;
Uncontrolled and haphazard urbanization of coastal areas across the region that result in use conflicts and impose great stresses on environment and resources
Input of largely untreated sewage into the coastal environment impacting on health, tourism and fisheries. Sewage treatment facilities are very limited throughout the region and raw sewage is discharges both into coastal lagoons and the rivers flowing into them. This, combined with the limited tidal water exchange of lagoon, has led to widespread eutrophication;
Discharges of untreated or partially treated industrial wastes directly into coastal water bodies that contaminate marine life and pose serious threats to human life.
Use of pesticides especially organochlorine group of compounds in agriculture and human health protection results in an input of residues to the coastal environment that are harmful to living resources; Risks from petroleum pipeline development and accidental spills of petroleum products and operational discharges from shipping (e.g. ship wastes) and the accidental introduction of toxic chemicals and exotic species that seriously damage the receiving ecosystem, leading to food and habitat loss; Harbour construction activities that generally alter long shore current transport of sediments and in many cases have led to major coastal erosion and siltation problems; Large amounts of sediments emptied by the many large rivers in this region that are important sources of nutrients and suspended matter to the coastal and marine environment contributing to eutrophication and harmful algal blooms with serious implications to ecosystem and human health; Apparent increase in the frequency and extent of coastal erosion placing fishing and other coastal communities in danger from loss of roadway and habitable lands.