The main species caught were Sardina pilchardus, Scomber japonicus and Trachurus trachurus. Other small pelagic and demersal fish were found only in small quantities and will not be dealt with in this report. In general the vertical distribution of the fish did not constitute a major problem for acoustic assessment of the biomass. At few times the fish was located at or close to the surface, but as this was a diurnal behaviour at some locations only, it is assumed that this undersampling can be compensated by including density figures from the repeated coverages when the fish was distributed below the surface layer.
Sardina pilchardus
The distributions of sardine during the main coverage and the two detailed coverages are shown in Figure 5, 6 and 7 respectively. The unit of the index is 0.1 × m2 per nm2. (energy reflected per unit area). The highest densities are found in the nearshore waters and the first main coverage does not sample these areas optimally.
Scomber japonicus
The mackerel was mainly found together with the sardine and then usually only as fractions of the total catch, except in an area northeast of Cape Juby where it constituted the main part of the biomass. Distribution during the main coverage is shown in Figure 8 and during the two detailed coverages combined in Figure 9.
Trachurus trachurus
The horsemackerel was generally found on the bottom and tended to have a more offshore distribution than the sardine and mackerel, except south of Tan Tan where it could be found in the more shallow waters, then only in small quantities. Distributions based on the main and the detailed coverages are shown in Figures 10 and 11 respectively.
