Guinea Current large marine ecosystem

September 20, 2011, 7:02 am
Source: NOAA
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Guinean fishermen. Source: Jett Thomason,

The Guinea Current Large Marine Ecosystem (LME) is characterized by its tropical climate. It owes its unity to the Guinea Current, an eastward flow that is fed by the North Equatorial Counter Current (NECC) off the Liberian coast.

Climate is the primary force driving the LME, with intensive fishing as the secondary driving force. Changes in ecosystem structure and species abundance have been observed in this LME.

The Global Environmental Facility (GEF) has funded a major program in the Gulf of Guinea. It is the largest single project presently underway in Africa for establishing an ecosystem-based assessment and management of coastal environments and resources.

Six countries from the Gulf of Guinea addressed transboundary issues from an ecosystem-based approach in a Transboundary Diagnostic Analysis (TDA). This was followed by the preparation and implementation of a Strategic Action Program (SAP). The project aims to increase the socioeconomic benefits of this LME’s natural productivity. The LME comprises all the African countries extending from the Bijagos Islands of Guinea-Bissau to Angola.

Productivity

The physical system of the Guinea Current is variable in both space and time and its dynamics are complex. Upwelling off the coasts of Ghana and Cote d’Ivoire occurs seasonally, with a weak upwelling around January to March, and intense upwelling from July to September (see Roy, 1995). For information on the LME’s long term variability induced by climatic changes, see Binet and Marchal, 1993.

The cold, nutrient rich water of the upwelling system drives the biology of the area extending from Liberia to Benin, and can be subject to strong seasonal, inter-annual and annual change, linked to the migration of the Intertropical Convergence Zone (ITCZ), the equatorial area at which the trade winds converge. For information on environmental forcing, the LME’s spatio-temporal variability, and the system’s boundaries, see Hardman-Mountford and McGlade, 2002, and Demarcq and Aman, 2002.

For physical-chemical changes in continental shelf waters of the Gulf of Guinea, see Koranteng and McGlade, 2002. These two authors suggest that the physico-chemical changes observed show interconnections between the eastern and western parts of the Atlantic Ocean, with warm climatic events being possibly linked with the El Niño Southern Oscillation (ENSO).

For more information on productivity, see McGlade, Cury, Koranteng and Hardman-Mountford, 2002.

For the link between environmental fluctuations and resource variability in the Guinea Current LME, see Roy, Cury, Freon and Demarcq, 2002. Entsua-Mensah (2002) discusses the important role of coastal lagoons and marine catchment basins in maintaining ecosystem productivity.

The Guinea Current Large Marine Ecosystem is considered a Class I, highly productive (>300 grams of Carbon per square meter per year (gC/m2-yr)), ecosystem based on SeaWiFS global primary productivity estimates. Through the GEF-funded project, a sustained survey of the productivity of the ecosystem has been cooperatively carried out, using ships of opportunity towing Continuous Plankton Recorders. This is providing information on the future availability of living marine resources for economic and food security purposes. The tows must be extended to the natural limits of the LME in order to build a comprehensive picture of productivity patterns on an ecosystem wide level.

Fish and Fisheries

The FAO 10-year trend (1990-1999) shows a catch of 950,000 tons in 1990 and 900,000 tons in 1999, with a marked decline to 700,000 tons in 1994 (click on the graph source for a review of capture trends and species groupings).

The LME is very rich in living marine resources commercially valuable fish, both marine and coastal. However, the LME shows evidence of ecosystem stress. There are major fluctuations of commercially valuable species. Significant changes in species composition have occurred over time. Several demersal and pelagic fish species are over-exploited.

More than 50% of the catch is composed of small pelagic clupeoids (herring, sardines, anchovies). For pelagic fish abundance, fish dynamics, variables such as SST and wind, and seasonal or inter-annual environmental changes, see Roy, Cury, Freon and Demarcq. For an overview of the fishery resources and fishery research in the Gulf of Guinea, see Mensah and Quaatey, 2002. For its section on fish ecology and fisheries, see McGlade, Cury, Koranteng and Hardman-Mountford, 2002.

Major fluctuations have been observed in the last two decades regarding the Triggerfish and Sardinella, two commercially valuable species in this LME. The almost complete disappearance of the Triggerfish after the late 1980s is attributed to observed environmental changes and upwelling intensification in the LME’s central part, off of Ghana and Cote d’Ivoire. There was a subsequent increase of the Sardinella, with unprecedented levels being reached during the 1980s (see Binet, et al., 1991). Such changes in fishery patterns appear, in part, to be related to overfishing, as evidenced by a decline in Catch-Per-Unit-Effort and taking of young immature fish by artisanal fishermen. Catch per Unit Effort (CPUE) is exceeding sustainable yields in some Guinea Current countries (see Ajayi, 1994).

Changes in fishery patterns also appear to be related to environmentally driven changes to pelagic stock distribution. The GEF funded project, aimed at ensuring long term sustainable use of the region’s shared living resources, is entering Phase 2. It will assess the oceanographic processes influencing the dynamics of fishery resources, affecting their growth, distribution and abundance. This will improve fisheries forecasting. Trawl surveys of 1996 and 1999 have led to regulatory actions for the region, such as restrictions in the licensing of fishing boats (except for tuna vessels, the tuna resource being under-exploited), the strict application of mesh sizes, turtle exclusion devices in trawl nets and more enforcement patrols in LME waters.

Species diversity and average body lengths of the most important fish declined (see FAO Review of the State of World Fishery Resources: Marine Fisheries - Eastern Central Atlantic). Despite the number of countries involved, joint regional policies and actions would offer the best approach to the effective and efficient management of transboundary fish stocks. These measures are expected to yield salutary results for the living resources, for marine conservation and biodiversity in the region. Subsequent surveys will determine stock levels, quantify biodiversity and assess contaminant loading in fish tissues.

For an evaluation of its progress in reducing habitat loss, preventing overfishing and reducing sources of environmental pollution, see The Gulf of Guinea Large Marine Ecosystem Project. The University of British Columbia Fisheries Center has detailed long term fish catch statistics for this LME. An FAO Document: Review of the State of World Fishery Resources: Marine Fisheries - Eastern Central Atlantic is also available for review.

Pollution and Ecosystem Health

There is strong evidence of serious degradation in the Guinea Current coastal environment. The main pollution problems are degraded water quality, the loss of critical habitats for migratory and non-migratory species, effluents in rivers flowing into the LME, the risk of offshore spills, marine debris and beach pollution, and industrial and solid waste.

The primary productivity surveys have revealed an increasing occurrence of harmful algal blooms indicating intense eutrophication and therefore excessive nutrient loading from anthropogenic sources.

The Global International Waters Assessment (GIWA) has issued a matrix that ranks LMEs according to the destruction and degradation of ecosystems, habitat and community modification, pollution and global change. GIWA characterizes the Gulf of Guinea as severely impacted in the area of solid wastes. This impact and other pollution indicators are increasing.

The GEF funded project is focussed on identifying the major transboundary environmental problems and reversing the degradation of the coastal and marine environment. The aim is to reach a consensus on methods for restoration and to initiate community based projects. For an evaluation of its progress in reducing habitat loss, preventing overfishing and reducing pollution from land based activities especially from industries, see these efforts and activities on Water Pollution Control in the Gulf of Guinea Large Marine Ecosystem.

A Water Pollution Control and Biodiversity Conservation project, completed in 1999, had as its development objective "to protect and restore the health of the Gulf of Guinea Large Marine Ecosystem and its natural resources", and to impact the relationship between coastal industry and the environment. Projects initiated include lagoon and mangrove restoration projects, a recycling of waste project in Ghana, the establishment of coastal and marine protected areas in Benin, and the control of leachate pollution from Togo’s phosphate mines. These mines are considered to be a major contributor of nutrients to the international waters of the Gulf of Guinea and beyond. Cote d’Ivoire is pioneering coastal erosion defense measures.

For a study of the LME’s health issues and efforts to control land based sources of pollution, see McGlade, 2002. Scheren and Ibe (2002) review the state of the environment in a regional perspective. For its section on pollution in this LME, see McGlade, Cury, Koranteng and Hardman-Mountford, 2002.

Socioeconomic Conditions

The over-exploitation of transboundary and migratory fish by large, industrialized offshore foreign fleets is having a detrimental effect on artisanal fishermen as well as on those coastal communities that depend on the near shore fisheries resource for food. For the evolution of trawling effort, both industrial and inshore, in the Ghanaian demersal fisheries, 1972-1990, see Koranteng, 2002, page 270.

Local communities are literally at risk if artisanal fishing cannot proceed. This becomes particularly serious in a context of exploding demographics in the coastal areas. Making more fish available to the 300 million people living in the region’s coastal communities, and earning much-needed foreign exchange from fisheries exports are project objectives. The region manifests many symptoms of unplanned and haphazard physical development as well as the effects of population pressures. Maritime transport, agriculture, urban expansion, the offshore oil sector and tourism are important economic activities.

The Guinea Current Project is the largest one in Africa aimed at increasing socioeconomic benefits. Addressing pollution problems will have immediate positive socioeconomic effects on the livelihood of coastal communities. For an assessment of socioeconomic circumstances related to environmental pollution, see Scheren and Ibe, 2002.

The restoration of lagoons, mangroves, estuaries, deltas and tidal wetlands—a major priority—is a long-term means to maintain the living resources that benefit local communities. All are critical habitats rich in natural resources and they are also filters for pollution. Assessing the magnitude of coastal erosion is a first step towards obtaining financial support to mitigate its causes. This is needed in order to stabilize cities, coastal settlements and economic infrastructures, including those linked to maritime transportation. For a study of the socioeconomic aspects of artisanal marine fisheries management in West Africa, see Bortei-Doku Aryeetey, 2002. For the role of women in fish processing and the fish “mammy” system in generating income and controlling the transport of marine fish to markets inland, see Akrofi, 2002. For demographic characteristics of the 6 Gulf of Guinea countries that first participated in the Project, see Ibe and Sherman, 2002, p. 28.

Governance

In the Gulf of Guinea Project, 6 countries, Cote d’Ivoire, Ghana, Togo, Benin, Nigeria and Cameroon, sought to strengthen regional institutional capacities to prevent and remedy pollution of the LME and the associated degradation of critical habitats.

In 1998, the environmental ministers of these 6 countries signed the Accra Declaration, as an expression of their common political will for the sustainable development of marine and coastal areas of the Gulf of Guinea. The countries identified the major transboundary living resources and management problems, and decided on a detailed survey of industries, a definition of regional effluent standards, an initiation of community based mangrove restoration activities, and a campaign for the reduction, recovery, recycling and re-use of industrial wastes.

The subsequent Guinea Current LME Project brought in 10 neighboring countries (Guinea-Bissau, Guinea, Sierra Leone, Liberia, Sao Tome & Principe, Equatorial Guinea, Gabon, Congo Brazzaville, Congo-Kinshasa and Angola). These countries are now in the process of expanding the TDA and SAP in collaboration with GEF, UNIDO, UNDP, NOAA and IUCN.

A review of Project Document is available from GEF/UNDP. Stakeholders in the petroleum industry, the fishing industry, tourism, agriculture, transportation and mariculture all share in the renewable and non-renewable resource base of this LME.

Efforts are being made to bridge the gap between government leaders, policy makers, managers, business people, scientists and academics, and grassroots communities. 500 scientists and policy makers have participated together and exchanged information in more than 40 workshops organized across the region. Actions include the joint identification of major transboundary resource problems, and the adoption of a common regional approach. For the role of national political factors in the management of this West African LME, see Prescott, 1993. For more information on the strengthening of regional institutional capacities and the international collaborations involved, see Ibe and Sherman, 2002. For a section on institutions and governance in this LME, see McGlade, Cury, Koranteng and Hardman-Mountford, 2002.

Nauen, 2002, examines some of the key institutional drivers that can help to support fisheries management. The participating countries are committed to reducing and controlling land-based sources of pollution in conformance with the principles of the Abidjan Convention on Cooperation for the Protection and Development of Marine and the Coastal Zones of West and Central Africa.

References

Articles and LME volumes

  • Akrofi, J.D. 2002. Fish utilisation and marketing in Ghana: state of the art and future perspective In: J. Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Binet, Denis and Emile Marchal, 1993. The Large Marine Ecosystem of Shelf Areas in the Gulf of Guinea:Long-Term Variability Induced by Climatic Changes. In Kenneth Sherman, et al. (eds.), Large Marine Ecosystems: Stress, Mitigation, and Sustainability (Washington, D.C.: American Association for the Advancement of Science, 1993) pp. 104-118. ISBN: 087168506X.
  • E. Bortei-Doku Aryeetey, 2002. Socio-economic aspects of artisanal marine fisheries management in West Africa. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Cury, P. and C. Roy, 2002. Environmental forcing and fisheries resources in Cote d’Ivoire and Ghana: did something happen? In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Demarcq, H. and A. Aman, 2002. A multi-data approach for assessing the spatio-temporal variability of the Ivorian-Ghanaian coastal upwelling: understanding pelagic fish stock dynamics. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • FAO, 2003. Trends in oceanic captures and clustering of large marine ecosystems—2 studies based on the FAO capture database. FAO fisheries technical paper 435. 71 pages.
  • Hardman-Mountford, NJ and JM McGlade, 2002. Variability of physical environmental processes in the Gulf of Guinea and implications for fisheries recruitment. An investigation using remotely sensed sea surface temperature. In: J. Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Ibe,C., AA Oteng-Yeboah, SG Zabi and D. Afolabi, 1998. Integrated environmental and living resources management in the Gulf of Guinea—the large marine ecosystem approach. Proceedings of the first regional symposium on the Gulf of Guinea Large Marine Ecosystem. UNIDO/UNDP/UNEP.
  • Ibe, C. and K. Sherman, 2002. The Gulf of Guinea Large Marine Ecosystem project: turning challenges into achievements. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Joanny, T. and F. Menard, 2002. Analysis of the spatial and temporal variability of demersal communities of the continental shelf of Cote d’Ivoire. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Koranteng, KA. 2002a. Fish species assemblages on the continental shelf and upper slope off Ghana. In: J. Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Koranteng, KA 2002b. Status of demersal fishery resources on the inner continental shelf off Ghana. In: J.Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Koranteng, KA and JM McGlade, 2002. Physico-chemical changes in continental shelf waters of the Gulf of Guinea and possible impacts on resource variability. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Le Loeuff, J and GSF Zabi, 2002. Spatial and temporal variations in benthic fauna and communities of the tropical Atlantic coast of Africa. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Lovell, AD and JM McGlade, 2002. Population structure of two commercially important marine species in and around the Gulf of Guinea. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Mcglade, J., P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford, 2002. The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • McGlade, JM, K.A. Koranteng and P. Cury, 2002. The EU/INCO-DC project: impacts of environmental forcing on marine biodiversity and sustainable management of artisanal and industrial fisheries in the Gulf of Guinea. In: J. Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Menard, F., V. Nordstrom, J. Hoepffner and J. Konan, 2002. A database for the trawl fisheries of Cote d’Ivoire: structure and use. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281
  • Mensah, MA and SNK Quaatey, 2002. An overview of fishery resources and fishery research in the Gulf of Guinea. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Nauen, C. 2002. How can collaborative research be most useful to fisheries management in developing countries? In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Pauly, D. 2002. Spatial modelling of trophic interactions and fisheries impacts in coastal ecosystems: a case study of Sakumo lagoon, Ghana. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Prescott, 1993. Role of National Political Factors in the Management of LMEs: Evidence from West Africa. In Kenneth Sherman, et al. (eds.), Large Marine Ecosystems: Stress, Mitigation, and Sustainability (Washington, D.C.: American Association for the Advancement of Science, 1993) pp. 280-291. ISBN: 087168506X.
  • Quaatey, SNK 2002. Research and extension linkages in Ghana’s agricultural development: the case of marine fisheries. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Roy, C., P. Cury, P. Freon and H. Demarcq, 2002. Environmental and resource variability off Northewest Africa and in the Gulf of Guinea: a review. In: J Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.
  • Scheren, PAGM and AC Ibe, 2002. Environmental pollution in the Gulf of Guinea: a regional approach. In: J. Mcglade, P. Cury, K. Koranteng and Nicholas J. Hardman-Mountford (eds). The Gulf of Guinea Large Marine Ecosystem--Environment Forcing and Sustainable Development of Marine Resources. Elsevier, 392 pages. ISBN: 0444510281.

Other References

  • Ajayi, 1994, The Status of Marine Fishery Resources of the Gulf of Guinea  : In: Proc. 10th Session FAO, CECAF, Accra, Ghana, 10-13 October 1994).
  • Bainbridge, V. 1972. The zooplankton of the Gulf of Guinea. Bull. Mar. Ecol. 8:61-97. Binet, Denis. 1983a. Phytoplancton et production primaire des regions côtiérs à upwellings saissoniers dans le Golfe de Guinée. Océanogr. Trop. 18:331-355.
  • Binet, Denis. 1983b. Zooplancton des régions côtiére à upwellings saisonniers du Golfede Guinée. Océanogr. Trop. 18:357-380.
  • Binet, Denis. 1988. Role possible d’une intensification des alizés sur le changement de répartitiondes sardines et sardinelles le long de la côte ouest africaine. Aquat. Living Resour. 1:115-132.
  • Binet, Denis, et al. 1991. Sardinella aurita de Côte d’ivoire et du Ghana: Fluctuations halieutiques et changements climatiques. In: Pêcheries ouest-africaines. Variabilité, instabilité e et changement, pp.320-342. Ed. by P. Cury and C. Roy. ORSOM, Paris.
  • Hisard, P. 1988. El Niño response of the tropical Atlantic Ocean during the 1984 year. Int. Symp. Long-Term Changes. Mar. Fish Pop. 1986. Vigo, Spain pp.273-290.
  • Houghton, RW and C. Colin, 1986. Thermal structure along 4 degrees W in the Gulf of Guinea during 1983-1984. Journal of Geophysical Research 91 (C10).
  • Mendelssohn, R. and Cury, P. 1987. Fluctuations of a fortnightly abundance index of the Ivoirian coastal pelagic species and associated environmental conditions. Can. J.Fish. Aquat. Sci. 44:408-421.
  • Pezennec, O., et al. 1993. La pêche des petites espèces pélagiques en Côte d’Ivoire. In Environment et ressources aquatiques de Côte d’Ivoire. I. Le milieu marin. Ed. by P. LeLoeuff, et al.. ORSTOM, Paris.
  • Roy, C. 1995. The Cote d’Ivoire and Ghana Coastal upwellings: dynamics and changes. In: FX Bard and KA Koranteng (eds). Dynamique et usage des ressources en sardinelles de l’upwelling cotier du Ghana et de la Cote d’Ivoire. ORSTOM edition, Paris.

 

 

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(2011). Guinea Current large marine ecosystem. Retrieved from http://www.eoearth.org/view/article/51cbedef7896bb431f694d76

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