Colombia
Figure 10 shows the distribution of fish along the shelf measured in units of the acoustic integration system. Densities are generally low with only small patches of somewhat higher values. The small aggregation off Punta Mala consisted of a species belonging to the sandeel family. Thread herring dominated off Buenaventura and this species was also present further north, but mixed with Pacific bumper and other jack mackerels, sierra, sharks and others. Off the Gulf of Cupica the main species included sea bass, scad and cutlassfish with fidel shrimp (Solenocera agassizi) caught at depths beyond 200 m.
Panama
Fish distribution by acoustic density intervals is shown in Figure 11. In the Gulf of Panama areas of high densities are as previously mainly encountered in the eastern, northern and western parts. They were however this time somewhat more extensive and yielded in several places higher density values than in Surveys I and II. Among the species found in higher abundance was thread herring usually found mixed with Pacific bumper, Spanish mackerel and others. The size of the thread herring was predominantly medium and small. There were good fishable concentrations off Pta. Brava, at about 15 fthms. depth in the Bahia de Panama and at 10 fathoms southwest of Islita Chame. Schools broke the surface in the afternoon. Figure 13 shows samples of echosounder recordings of pelagic fish from the two last mentioned areas with schools of thread herring and the accompanying species. The small patch east of Isla Galera in Figure 11 represent anchovy of smallish size found in dense layers and schools at 50-80 m of depth. The wider area of medium dense fish found in the central southern part of the Gulf seemed to consist mainly of scads (Decapterus macrosoma) with some round herring and butterfish. The small dense patches further east probably also represent scads. Demersal fish was recorded over hard bottom inshore south of the Pearl islands.
Recordings along the western coast of Panama were as previously less abundant. A minor aggregation inshore west of Punta Mala consisted of anchovy, carangids and Spanish mackerel and the small concentrations in the inner parts of Golfo de Coiba and Golfo de Chiriqui consisted mostly of anchovy, thread herring and predators such as barracudas and Spanish mackerel. Bottom fish was recorded in some abundance over the Hannibal Bank.
Costa Rica
Figure 12 demonstrates the fish distribution as observed by the acoustic system. In general the picture is similar to the distributions found in the previous surveys. In Golfo Dulce there is only scattered fish in the entrance and near the surface. Some fish aggregations inshore in Bahia Coronado and from Pta Quepos westwards past Pta Judas seemed to consist of small and partly juvenile anchovy accompanied by predators such as barracudas, sierra and snapper and other demersal fish. The densest concentrations were as usually found in Golfo de Nicoya here also dominated by small anchovy and predators including carangids. Further along the coast fish aggregations were only located inshore and consisted of snapper, carangids, sierra and ancovy. Navigational conditions are here difficult and the shallower waters were incompletely covered. A small aggregation of seabass was located offshore west of Pta Helena.
