The working group made the following recommendations, listed in decreasing order of priority:
- At the earliest possible date, the Tema Fishery Research Unit should begin to extrapolate size frequencies to the total catch between 1976 and 1978 with a view to including them in the final report (Appendix 5). Also as soon as possible, the Fishery Research Unit should present data available on catches, effort and cpue of the artisanal fisheries once they have been grouped by month;- In future, measures should be taken to have basic calculations available before meetings on size frequency of catches, distributions of effort per stratum, catch and cpue for recent years and, where necessary, historic data. This could be achieved by means of exchange of scientists, between the three countries, for a few days several months before the official meeting;
- Areas of information gathered and processed should be extended to obtain cpue for the Ghanaian fisheries per category of boat, per month and per sector with the aim of being able to better calculate abundance indices. By means of this information it would moreover be possible to calculate recruitment by analysing the yield of beach seine and poli nets. In the case of Ivory Coast it is vital to estimate at least catches of the artisanal sector;
- In all three countries routine measurements of sardinella landed by each fishery should be initiated or continued to obtain continuous series of data;
- Collection of other biological parameters should be carried out in the same way, particularly as regards gonadosomatic indices;
- Echo-integration surveys should be carried out in March-April-May where possible on an annual basis, with species identification. Results of these surveys, as well as other stock abundance indices, could be used to avoid overfishing;
- A detailed study on the phenomenon of the rapid disappearance should be carried out by an expert;
- Variation in intensity of upwelling, and more especially its geographical extent, should be studied together with surface currents so as to gain a better grasp of the problems of abundance and availability variations as well as those of larval survival. One means of achieving this is to have the data sheets on surface temperatures, winds and current of the Merchant Navy examined by the Statistics Office of ORSTOM, Brest, France; data for the northern CECAF zone could be analysed at the same time (FAO, 1979c). Results should then be interpreted in the laboratories in the region;
- The mechanism of upwelling should be clarified (study of currents, internal waves and winds);
- Extensive plankton surveys should be carried out in view of the variability of S. aurita reproduction, and also the relationship between phytoplankton and juveniles of each species should be studied;
- A recruitment index should be estimated by analysing data on bait catches by Japanese tuna bait boats operating in Ghana since 1967. The working group recommends that Ghanaian authorities contact Japanese research workers to obtain these data;
- Assuming that there is a relationship between sardinella and B. capriscus stocks, studies on the biology and population dynamics of B. capriscus should be continued so as to determine exactly the migratory patterns of this species and the possibilities of its preying on S. aurita eggs and larvae during the spawning period. The quantity of B. capriscus discarded should also be estimated;
- Interaction between S. aurita and other species should be studied at both the biological and fisheries levels, particularly as regards B. capriscus as noted above, S. maderensis and A. guineensis;
- Finally, data obtained from Ghanaian experimental trawler should be studied to assess the biological and economic importance of the adult sub-stock of S. aurita.
