Variations saisonnières des facteurs hydrologiques et du biovolume microalgal benthique au sein d'un habitat artificiel (acadja-enclos) dans la lagune Ebrié: site d'Adjapoté

This paper presents the results of a comparative study of chemical and physical characteristics (temperature, oxygen, salinity, turbidity, pH, nutrient: phosphates, nitrates, nitrites, ammoniac) within the extensive aquaculture structure (acadja-enclosure or artificial habitats for fishes) and in the surrounding water. Biological characteristics of the periphyton growing on bamboos from acadja-enclosure were also described.

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 The purse seines (15-30) have been superseded by "syndicat" seines (15) in 1990.

Linefish resources annual report for the year 2000. Part 3: towards a management plan for the Mozambican line fishery

The dependence of Mozambique on its marine resources is highly significant. There is a need for a plan of action for sustainable use of these important resources, for the benefit of the nation. In this document, some aspects are included, that can be important to take into consideration for a sound action plan for the lin fishery of Mozambique.

Rélation longueur céphalothoracique-poids total chez Penaeus duorarum (Burkenroad) en Côte d'Ivoire

This short note gives the results of the measurements of cephalothoracic length-total weight of Penaeus duorarum in Côte d'Ivoire and compares those data to the ones collected in Senegal (Bondy 1968) and in the Gulf of Mexico (Kutkuhn 1965).

La pêche crevettière en Côte d'Ivoire. Bilan 1969-1970 et perspectives

The evolution of the fishery of the pink shrimp Penaeus duorarum Burkenroad is analysed from its beginning in 1969 until the end of 1970. A rapid and general decline of the yield has been evident during this period. The actual shrimp fleet seems to be too big to allow an exploitation economically convenient of the stock.

La pêche au chalut en Côte d'Ivoire. Maximum de rendement économique

This paper analyses the relations between effort and catch per unit effort of trawlers which worked in Côte d'Ivoire from Jan 1966 to Dec 1970. A fishing effort permitting to exploit fishery in the best rentability conditions is proposed.

Biologie et dynamique d'un Sciaenidae ouest-africain Pseudotolithus senegalensis (V.)

In relation to the hydroclimate prevailing off Congo (B) and Côte d'Ivoire, synchronic variations are described in abundance and distribution of Pseudotolithus senegalensis V., economically the most important species in the West African trawl fishery. Although this fish prefers the warm surface layer, it is relatively indifferent to hydrological conditions, since it may also occur in the thermocline down to the higher levels of 'Central South Atlantic Water'. The oxygen concentration appears to have an important effect upon their distribution, especially the low concentrations occurring with the upwelling. The main biological functions, such as spawning and recruitment times, condition factor, diet and ring appearance on otoliths, also follow cycles, which are parallel with the hydroclimate one. Therefore, the ring-shaped structures revealed by burning previously ground otoliths could be easily interpreted. Thus, an accurate method for ageing tropical fish is now available. From the age determinations for the Congolese stock, it appears that growth is fast and total mortality rate high. An influence of fishing effort, which increased 3 times during the exploited phase of sampled specimens, appears both in growth and in total mortality. From there an estimate for the fishing mortality could be given. The estimates of dynamic parameters for the Congolese stock are then used in the Beverton-Holt model. A valuable increase of the yield could be expected, if mesh size is widened and effort restricted.

Standardisation des efforts de pêche des chalutiers ivoiriens et estimation de l'abondance relative dans les divers secteurs

The method developed by Robson (1966) is used to standardize fishing effort of Côte d'Ivoire trawlers whose size and power are very different. This method also allows the estimation of the relative abundances in the different fishing areas. The results obtained using 10 years data show that the entire Ivorian continental shelf can be considered as a single fishery unit. The relative fishing power of vessels is well correlated with gross tonnage, brake horse power and length of the vessel. The obsolescence of the trawlers affects their fishing power.

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).

Contribution à l'écologie de quelques taxons du zooplancton de Côte d'Ivoire. 3 - Larves de décapodes et lucifer

The warm season is the abundance period of the planktonic larval stages of Decapod Crustacea and of Lucifer faxonii in Ivoirian waters. Two or three maxima occur each year during the enrichments interrupting the warm and oligotropic season: February (small upwellings), June - some years - (first rains) and September - November (flood of rivers, end of cold season). Vertical distribution follows seasonal variations and varies little among the taxons. In a general way, Decapod larvae and Lucifer inhabit superficial layers in cold season and sink down during the warm season. It allows them to follow the maximum of primary production. Lucifer faxonii is breeding almost the year long. Breeds succede at rate of 3,7 weeks approximately.

La circulation superficielle dans la partie occidentale du Golfe de Guinée

Direct current measurements carried out for 10 years in the Gulf of Guinea clearly show the importance of transverse circulation. The general pattern of currents is characterized by an anticyclonic gyre. The seasonal variations of this circulation are calculated through the study of the 3-monthly averaged geostrophic currents. The biological consequences of such a circulation are outlined.

La pêche industrielle des poissons démersaux en Côte d'Ivoire. Généralités, localisation, homogéneité relative des zones de pêche ivoiriennes

This paper describes the fishery of Côte d'Ivoire and its evolution to the present day. The location of fishing off Côte d'Ivoire is specified for each area and each type of trawler. A comparison of productivity between the different areas shows disparities that allow to make clearer the repartition of effort of all types of trawlers in each area. The Côte d'Ivoire continental shelf is populated with demersal stocks of homogeneous densities.

Marquages de Penaeus duorarum notialis en Côte d'Ivoire. 3 - Croissance

The occurrence of seasonal variations in growth is confirmed. The mean annual growth curve obtained is not different from that obtained by modal progression analysis. The comparison with results obtained by other authors in Florida did not permit to point out any sensible difference and the author concludes that the phenomena are quite similar but that it would be better, for yield computations, to use the observed age-length keys instead of the computed parameters.

Simulation stochastique des structures démographiques. Application aux populations d'albacores, Thunnus albacares

A computer program has been written in order to generate a population of fishes following a Von Bertalanffy growth curve with a random Gaussian variability for birth dates and growth parameters K and L ∞. Standard deviations for these 3 parameters are chosen separately for each run. Fishing and natural mortalities are applied to this population. Using as an input parameters usually taken for yellowfin in the eastern Atlantic, the simulation suggests a standard deviation between 1 and 2 months for the birth dates in this population. It also indicates that increasing levels of fishing mortalities must produce a better agreement between age and length for the larger fish.

Zooplancton et micronecton dans la région du Dôme d'Angola en février-mars 1971 et rélation avec les thons

Diurnal variations and geographic distribution of zooplankton and micronekton are studied in the Angola Dome. The small zooplankton species (Copepodids, Copepods, Amphipods, Ostracods, Chaetognaths, etc.) undertake vertical migrations within a 100 m water layer. Most of the micronekton species are below this layer during the day and move towards the surface during the night. The whole region prospected is rich in zooplankton and micronekton species that are present in the upper 100 m layer during the day. Only the South-West region is poor. On the contrary, this latter region is abundant in species that migrate below this layer during the day. The authors think there are 3 main difficulties in establishing good relationships between micronekton and tunas distribution: 1 - inability of micronekton nets to catch the tunas preys; 2 - the great diversity of tunas food; and 3 - the too large delay between micronekton studies and those of stomach contents of tunas.