The new data submitted to the two meetings (Casablanca and Dakar) show that total sardine catches in Division 34.1.3 during the present decade have been much greater than might have been thought at the first meeting of the Special Group. This made it necessary to recalculate the evaluations. In addition, the information available shows that major changes have occurred in the hydrological regime of the sector since the start of the 1970s - changes affecting particularly the intensity of upwelling in Division 34.1.3. At the same time modifications have also been observed in the southern distribution limit, in the growth rate and in the size and apparent recruitment of the sardine concentrations present in Division 34.1.3. The statistics (catch and fishing effort) also suggest that far-reaching changes have occurred in the distribution of sardine between Zones A and B. These biological changes may be connected to the fluctuations in upwelling. It is equally possible that an inverse evolution may occur should the hydrological regime return to its previous state.
In any event, these natural fluctuations greatly complicate evaluation of the state of exploitation of the sardine stock. Analysis of the cpue and of effort has been possible only for a relatively short series of data relating to Zone C. This analysis suggests that, insofar as this stock is distinct from the concentrations fished in Zones A and B, the catches in this zone are close to the maximum potential. The cohort analyses, still imprecise owing to deficiencies in catch statistics and age determination, lead to very similar conclusions. Yet from calculations based on comparison of the Polish cpue, the Soviet research workers reach decidedly more optimistic conclusions.
For Zones A + B, comparison of the total catches with biomass estimates drawn from acoustic surveys covering most of Zones A and B suggests that the fishing mortality rate (which, in a situation of equilibrium, is equal to the catch divided by the annual mean biomass of fish of exploitable size) is moderate. Although, it should be emphasized, the acoustic estimates may include a considerable proportion of specimens below the size of first catch - all the more so in that recruitment to the fishery seems to occur in a very progressive fashion (Figures 3, 6 and 10) - and it is therefore not possible to make any accurate estimate of the fishing mortality rate on the basis of these data alone, it does seem that exploitation of the stock or stocks present in these zones has not yet reached maximum production level. The cohort analyses made during the Dakar meeting are not much more reliable but lead, independently, to conclusions of exactly the same kind.
These observations, as well as those relating to the probable change in the distribution of sardine concentrations between Zones A and B (Section 7), suggest that the recent decline in catches experienced by the Moroccan fishery is not due to excessive fishing but essentially to natural phenomena.
