Bibliographie des lagunes et du littoral de Côte d'Ivoire (Afrique de l'Ouest)

The present bibliography collects references on lagoon and coastal environments in Côte d'Ivoire. It is mainly based on: - the draft bibliography prepared by Charles-Dominique and Durand in 1979, edited in the Archives Scientifiques du Centre de Recherches Océanographiques d'Abidjan (vol. 5 no. 2); - the synthesis on the marine environment, published in 1993 (LeLoeuff, Marchal and Amon-Kothias editors); - and the synthesis on the lagoon environment, published in 1994 (Durand, Dufour, Guiral and Zabi editors). In spite of a careful check of the available documents, it is more than possible that references are lacking or erroneous. That's why this bibliography is still a draft, and the author will be glad to receive complements and/or corrections from lectors. After these contributions, a more comprehensive version will be proposed. Remarks can be sent to this e-mail: arfi@ortsom.orstom.fr or to the postal address.

Synthèse des travaux effectués au CRO sur les végétations envahissantes flottantes (1985-1990). Propositions et recommandations

The present document represents a synthesis of the scientific knowledge gathered by the CRO in the years 1985-1990, and related to the proliferation of aquatic macrophytes, commonly called floating aquatic weeds, in the Ebrié lagoon.

Suivi cartographique de l'expansion des macrophytes envahissant le système lagunaire Ebrié (Côte d'Ivoire)

Remote mapping were realised from December 1986 to September 1989 to describe the seasonal evolution of macrophytes colonizing the surface waters of the eastern sector of the Ebrié lagoon. The vegetal cover of this sector and associated lagoons is essentially composed of Eichhornia crassipes (water hyacinth). Its expansion is favored by the decrease in the salinity of the lagoon waters which is due to rain falls. Its migration through the lagoon environment is ensured by the overflow of the Comoé river. The opening of the Bassam inlet induced its temporary disappearence from the newly created estuarian zone.

Contribution à l'étude des modifications hydro-sédimentaires consécutives à la réouverture artificielle de l'embouchure du Comoé à Grand-Bassam

The Bassam artificial inlet was opened (in September 22, 1987) in order to revacuate offshore invasive aquatic plants. This has considerably modified the hydro-sedimentary environment of the lagoonal domain at Grand-Bassam. Tidal currents effect has confered the lagoonal waters an estuarine feature, the saline intrusion (25-35%o) increased beyond the Moossou bridges up to the confluence of the Comoe river. This has led to a cleaning of the river lower course and above all to the bottoms of the lagoon, which were previously confined. The remobilization of mud (from lagoonal bottoms around Bouet Island) evacuated offshore, has exposed lagoonal and oceanic sandy features. This new system remains fragile, with the seasonal (low river-flow) clogging.

Les effets de la réouverture de l'embouchure du fleuve Comoé sur le végétation littorale lagunaire (Lagune Ebrié - Côte d'Ivoire)

The results of floristic data collected during two surveys in the eastern region of Ebrié lagoon in 1987 (before the reopening of the inlet) and in 1988 (after the reopening of the inlet) are discussed in this article. Salinity increase (from 4‰ to 30‰) as a result of the reopening in September 1987 of the channel of Comoé river, profoundly modified qualitatively and quantitatively, the plant population. Floating or fixed macrophytes have been completely destroyed. Mangrove forest being the hydrophytic belt of the lagunar rives.

Doses efficaces en glyphosate et en 2,4-D pour le contrôle chimique des laitue d'eau (Pistia stratiotes, Linn.) et toxicité du glyphosate vis-à-vis des tilapias (Sarotherodon melanotheron)

The toxic effects of two herbicides Round up (gliphosate) and 2,4-D (herbazol) were tested on Pistia stratiotes (Linn. Araceae) samples cultivated in glass aquariums. The gliphosate appears to be more toxic on Pistia Stratiotes than 2,4-D. It was then tested on tilapia Sarotherodon melanotheron juveniles. The lethal dose for tilapia (CL50 = 13.25 mg.l -1) is about 18, 37 and 74 times higher than the glyphosate toxic dose for plants at 1, 2 and 4 meters water depth respectively.

Note sur les baleines échouées en estuaires artificiels en Côte d'Ivoire

Stranded whales in estuarine waters were identified in Côte d'Ivoire: the Spermwhale, Physeter catodon L. 1758 and the Finwhale, Balaenoptera physalus L. 1758.

Statistiques de pêche en lagune Ebrié (Côte d'Ivoire): 1976 et 1977

In the Ebrié lagoon fishes are mostly caught by means of 6 kinds of fishing gear: small and large mesh gillnets (respectively 1.5-2 and 6.5-8 inches stretched mesh), cast-nets and multi-hooked lines for individual fishermen, and beach seines and ring-nets for collective fishing. Statistical data gathered during 1977 allowed an estimation of total catches: about 6700 tons. The bulk of the catch, 4800 tons, came from beach nets and ring nets, the contribution of which is nearly the same. Individual fishing gear, small mesh gillnets repesenting the main part, account for 25 to 30% of total catch; about 1900 tons for year 1977. Six species, or species groups, comprise more than 85% of the catch. In the Abidjan area, where marine influence is the more noticeable, ring nets are more numerous and their catches increased since 1975. On the other hand, fish captures in unsalted and brackish waters seem to show a stagnancy and a decrease in fish lengths; this phenomenon is probably in connection with beach-seine excessive fishing effort and/or their small meshes (one inch stretched).