Méthodes des mesures des biovolumes, poids secs, poids secs sans cendres et des éléments C, N, P du mésozooplancton utilisées au C.R.O. d'Abidjan

Methods for the estimation of zooplankton biomasses, used in the Oceanographic Research Center of Abidjan are presented. They deal with settled and displacement volumes, dry weight and ash-free dry weight, elementary carbon, nitrogen and phosphorus composition. The dry weight method is detailed: elimination of salt by a fresh water stream, preservation of dry samples at -20 degrees Celsius, rehydration during weighing. A few comments on the 'CHN' analysed values are made: at 1,100 degrees Celsius, most of the carbon is organic, only 10% of the mineral fraction being analysed.

Sternes réprises en Côte d'Ivoire au cours des hivernages 1973-1974 et 1974-1975

Data are reported on: (1) date and place of ringing the juveniles and adults of the sea bird of the genus Sterna in Côte d'Ivoire, and (2) date and place of recapture during the winter periods of 1973-74 and 1974-75.

Sternes réprises en Côte d'Ivoire au cours des derniers hivernages des années 1969-1970-1971-1972-1973

Data are reported on: (1) date and place of ringing the juveniles and adults of the sea bird of the genus Sterna in Côte d'Ivoire, and (2) date and place of recapture during the winter periods of 1969, 1970, 1971, 1972, 1973.

Biologie de Penaeus duorarum en Côte d'Ivoire. 3. Étude des variations quotidiennes des rendements et leur relations avec l'hydroclimat. Essai de généralisation au Golfe de Guinée

Hydroclimatic conditions in the Gulf of Guinea between Senegal and Nigeria are briefly described emphasizing the seasonal variations of transparency. Analysis of the Abidjan based shrimp fleet allowed to the description of the seasonal variations of activity rhythms for Côte d'Ivoire, Ghana, and Nigeria. These rhythms are different between seasons, between fishing grounds, and sometimes even between depths on a given ground. These variations follow the turbidity ones. Diurnal activity is observed in very turbid waters, nocturnal and transition activity in clearer ones. The authors assume that the basic behaviour is a nocturnal one, but that the shrimp-trawlers catches reflect some apparently different ones resulting from diel variations in the stock availability. To explain the apparently diurnal behaviour observed most of the year over the whole Gulf of Guinea it is suggested that these generally benthic shrimps become nectonic at night when turbidity is very high. The results obtained in Ivory Coast, Ghana and Nigeria are compared to those from Senegal where hydroclimatic conditions are different. The similarities are emphasized. The differences in observed behaviour are supposedly caused by the cold season water temps which are sufficiently low to disturb the nor mal activity rhythm.

Choix d'une unité d'effort de pêche pour les flottilles sardinières sémi-industrielles et artisanales au Sénégal

Different catches per unit of effort available for industrial and artisanal sardinella fisheries of Senegal have been analysed and compared in order to determine whether they are acceptable indices of abundance. Among the four units of fishing effort studied (total number of sets, number of trips, time spent on fishing ground, searching time), the first and the second seem inadequate in the studied fleets. The two other units, particularly the searching time, allow the calculation of catches per unit of effort which best reflect variations in abundance, although they are not completely free of usual deficiencies.

Compte rendu de la campagne Echobal I n/o Capricorne du 18 âout 1980 au 24 âout 1980

This paper related an echosounding survey located off Côte d'Ivoire in cold season 1980. Biomass mean for the continental platform (20-125m) was 15 metric tons for one square mile.

Comparative efficiency of trawls made of nylon, polyethylene monofilament and tape twines

Results of comparative fishing operations conducted with three nets of identical design made of nylon, twisted polyethylene monofilament and high density polyethylene (HDPE) tape twines are presented in this communication. Since the tape net recorded the highest prawn and fish catch, monofilament and nylon following in order, it can be recommended to the fishing industry as one of the cheapest and effective fishing materials evolved for trawl fabrication.