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.

Influence de la réouverture du canal de Bassam sur la pêcherie de crabes de Vitré II en Lagune Ebrié (Côte d'Ivoire)

This work is the result of one year of investigation from May 1987 to June 1988 among fishermen of Vitré II village located in the eastern region of the Ebrié lagoon.

Communication mer-lagune: impact d'une réouverture sur l'ichtyofaune de la lagune Ebrié (Côte d'Ivoire)

The artificial reopening of the lagoon inlet, made in Grand-Bantam in September 1987 in order to reduce the aquatic weeds proliferation, induced some environmental and fish communities alterations in the eastern part of the Ebrié lagoon (Côte d'Ivoire). A preliminary field survey made in May 1988 shows an increase in the salinity rate and an increase of the marine component among fish communities, when compared to the former ecological state of this lagoon area (reference data of 1980 and 1981).

Reproduction de Ethmalosa fimbriata (Bowdich) en lagune Aby (Côte d'Ivoire)

Ethmalosa fimbriata (Bowdich) is the most abundant clupeid in the Ivorian artisanal fisheries. It represents over 60% of lagoon catches. In Aby lagoon the size at first sexual maturity is situated at 9.6 cm for male and 9.9 cm for female. The reproduction takes place twice a year during the high salinity periods from February to May and July to August. This reproduction does not affect significantly the sex-ratio, the mean of which varies from 35% to 36%, depending the period. The fecondity is very fluctuating and varies from 11000 eggs to 148000 eggs per female.

Les macrophytes aquatiques des berges lagunaires

This synthetic article describes the composition and organization of vegetations colonizing the Ebrié lagoon banks and provides original data on the recent evolution of this association consecutively to the accidental introduction of 2 new species of floating macrophytes (Salvinia molesta and Eichhornia crassipes).

Estimation des niveaux de pollution organique et bacterienne des eaux à proximité des berges de la ville d'Abidjan (Lagune Ebrié - Côte d'Ivoire)

This article presents the results of three surveys, which were undertaken in order to estimate the levels of organic and bacterial pollutions of the Ebrié lagoon banks in the urban area of Abidjan.

Reproduction et fécondité du machoiron Chrysichthys nigrodigitatus en élevage

Different rearing facilities (concrete tanks, pens and ponds) were tested for suitability as spawning environments. The concrete tanks and the pens in the lagoon gave the best results as to the number of spawns obtained. Of the three types of spawning devices tested, containers with a 150 mm opening at one of the two ends were preferably used by the fish. The brooders in the spawning facilities spontaneously entered the spawning containers to deposit their eggs without external human intervention. Actual fecundity estimates ranged from 9805 to 40597.

Cycle sexuel et fécondité du machoiron Chrysichthys nigrodigitatus en Lagune Ebrié, Côte d'Ivoire

Changes in the seasonal development of the gonads of female Chrysichthys nigrodigitatus, in Ebrié lagoon (Côte d'Ivoire) are described over an annual reproductive cycle. Seven macroscopic stages of gonad maturity were identified. There is a major spawning period from July to November. The mature fish spawn only once during the breeding season. There was a slightly higher correlation between fecundity and fish length than between fecundity and fish weight or gonad weight. Fecundity estimates ranged from 5438 to 36257 eggs and from 4878 to 87724 eggs, respectively for the fish in captivity and those in the natural environment.

Essais d'utilisation de "nourrisseur à la demande" pour l'alimentation de Chrysichthys nigrodigitatus en cage-enclos

An experiment using demand feeder was carried out on the catfish Chrysichthys nigrodigitatus reared in cage-enclosure in the lagoon Ebrié (Côte d'Ivoire). The study lasted 5 months, from October to March, and showed that the demand feeder improves the growth rate of the fish and the feed conversion. It was able, as well as the conventional hand feeding, to show monthly variations of performances.

Variations temporelles de Vibrio cholerae Non 01 et conditions environnementales dans un site aquacole (Lagune Ebrié, Côte d'Ivoire)

The annual cycle of Vibrio cholerae in the environment surrounding the Layo aquaculture facility (Ebrié lagoon) was studied from March 1991 to April 1992. Vibrio cholerae counts were coupled with the determination of physical and chemical characteristics of water and the estimation of biological richness of this environment.

Statistiques de pêche en Lagune Aby (Côte d'Ivoire): évolution de l'effort et des captures de 1979 à 1990

Two kinds of fishing gears insure the exploitation in Aby lagoon: the individual gears are represented essentially by gill nets and collective gears by seines. The number of gill nets varies between 1500 in 1981 and 5600 in 1986. The beach seines, which number varies between 40 and 60, are regularly used. The purse seines (15-30) have been superseded by "syndicat" seines (15) in 1990.

Abordagem de grupos funcionais no estudo da dinâmica fitoplanctônica da Lagoa de Marapendi, Complexo Lagunar de Jacarepaguá, RJ

A Lagoa de Marapendi é uma lagoa eutrófica do complexo lagunar de Jacarepaguá, Rio de Janeiro. Como conseqüência ao constante e acelerado processo de eutrofização vigente, houve uma mudança na estrutura de sua comunidade fitoplanctônica, o que pode ter um importante significado para diversos componentes do ecossistema, além de inviabilizar diversos usos. Este estudo visou reconhecer os padrões espaciais e temporais do fitoplâncton, identificando os fatores controladores e direcionadores da comunidade, através da comparação entre as abordagens dos grupos taxonômicos e dos grupos funcionais. Foram coletadas amostras mensais em 4 pontos ao longo da lagoa no decorrer do ano de 2008. A análise florística revelou a presença de 45 táxons pertencentes às classes Cyanophyceae, Cryptophyceae, Chlorophyceae, Bacillariophyceae e Dinophyceae. Estes foram alocados em 10 grupos funcionais (GF) sensu Reynolds (H1, K, M, S1, X1, X2, J, C, MP e Y) e em 6 grupos funcionais baseados na morfologia (MBFG). Os dados de biomassa para todas as abordagens testadas foram comparados, juntamente com as variáveis abióticas, através de análises multivariadas de redundância (RDA). A abordagem de GF mostrou ser mais rica em detalhes, evidenciando diferentes estratégias adaptativas de grupos ecológicos de cianobactérias. Contudo, para ambientes eutróficos, rasos e com poucas espécies, tal qual a Lagoa de Marapendi, a utilização da abordagem de MBFG mostra ser mais adequada devido à sua simplicidade de utilização, aliada à boa capacidade de explicação da dinâmica fitoplanctônica.

História ambiental e paisagens simbólicas no município de São Pedro da Aldeia (RJ): a Lagoa de Araruama e a Serra de Sapiatiba

Este trabalho visa contribuir com os estudos de História Ambiental e de Geografia ao abordar a interação entre os aspectos culturais e a natureza da Lagoa de Araruama e da Serra de Sapiatiba, localizado no Estado do Rio de Janeiro. A pesquisa propõe uma análise das paisagens simbólicas do município de São Pedro da Aldeia (RJ) por intermédio do 3 nível da História Ambiental. Além de caracterizar estas áreas como paisagens simbólicas inseridas na Região dos Lagos numa Área de Proteção Ambiental (APA de Sapiatiba), destaca-se a importância do capital imaterial e da história ambiental na conservação da diversidade de um pequeno fragmento de Mata Atlântica e também da natureza das águas em um importante trecho da maior lagoa hipersalina do mundo. Portanto, nosso objetivo neste estudo é desvendar a História Ambiental da Lagoa de Araruama e da Serra de Sapiatiba no município de São Pedro da Aldeia (RJ), a partir da análise da transformação da paisagem.

La pollution bacterienne de la lagune et de la mer autour d'Abidjan

The total coliforms, fecal coliforms and fecal streptococci were counted over 1 year at 33 stations in the Ebrié Lagoon near Abidjan (Ivory Coast). Most of the waters show high numbers of bacteria, (D category of the American standards). For the sea-beaches, high numbers of fecal germs are found where the human population is abundant.

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).