Environment: it seems that there had been a global change in the wind level with a reinforcement of its mean intensity, a favourable modification with respect to productivity of the ecosystem. From the major cold season of 1987 to that of 1989, there were low upwelling indices but the minor cold season of 1990 was very intense and widespread in time and space.
State of the Sardinella aurita stock: Considering the favourable state of the environment at the beginning of 1990 and the good catches and CPUE these last years, the working group had no reason to state that the stock or stocks of the round sardinellas were in poor condition.
Physical oceanography:
to pursue the study of remote sensing data in order to draw a quantitative evaluation of the intensity of the upwelling;
to study the possibility of collecting data on currents (direct measurement or models);
to maintain the collection of data on river flow in Côte d'Ivoire and to identify the sources of such data in Ghana;
to look, in Ghana, for the sources of data on winds;
to maintain the collection of temperature data at the centres in Ghana and Côte d'Ivoire, and to set up such a collection in Togo and Benin.
Statistics:
to establish, for the Ivorian beach-seine, a sampling plan for catch and effort data and to pursue the collection of samples on length frequencies;
it would be useful to know the sizes of the fish caught by the Ghanaian beach-seines, and to have an idea of the proportion of juveniles;
for the ali, poli and watsa nets in Ghana and Côte d'Ivoire, to intensify the collection of length frequency data in all sectors with a strategy which will allow a correct extrapolation to the total catch. Given the different selectivities of the three gears which are often used at the same time, it is fundamental to develop sampling systems which would allow the exact correspondence of sampling lengths and the corresponding catches;
in Côte d'Ivoire, to work on the existing beach-seine statistics at the Alladjan beach;
to regularly update the database established for the working group. With this frame, the compilation and analysis of the data on a fine spatia-temporal scale should be carried out.
Biology:
to study the growth of the chub mackerel and the flat sardinella from the use of length frequency data of Ghana and Côte d'Ivoire;
to carry out analyses of gonado-somatic indices and length-weight relationship of S. aurita;
to identify the possible populations of S. aurita by genetic and biological methods.
Research:
to carry out a multivariate analysis (compilation of the correspondence and hierarchical analyses) on the spatia-temporal data which were visually analyzed during the working group, in order to extract the factors which could explain the variability of the observations. This seems essential for the identification of the zone-month-gear strata to enable the calculations of reliable indices of abundance for the principal species. Such a study could be organized by CECAF.
to define the spatia-temporal strata for the calculation of abundance indices of S. maderensis (zone-month-gear) and S. aurita (zone-month); for the anchovy, it would be interesting to consider the indices of abundance of Togo and Benin given the character of species-targeting in these countries.
Other matters
to organize such a meeting in April/May in order to have the maximum completed data of the previous year;
to include in the next working group, the species Ilisha africana, the catches of which are very important in Benin.
