Colombia
Figure 10 illustrates the distribution of all fish as observed with the acoustic integration system. The unit of fish abundance is 0.1 m2 per nm2 acoustic reflection. In areas of high productivity, densities in the range 100-300 were defined as dense, while figures exceeding 300 were considered as very high fish densities. As seen in Figure 10, none of the recordings during the survey off Colombia falls in these two higher categories. Apart from scattered occurrences of fish, which was found in patches along the coast, only a few aggregations were recorded. These consisted mainly of Pacific anchoveta (Cetengraulis mysticetus), thread herring (Ophistonema libertate), different anchovies (Anchoa spp.) and Pacific bumper (Chloroscombrus orqueta). In the deeper water, the fish fauna was dominated by the argentine (Argentina aliceae) and Pacific butterfish (Peprilus snyderi).
The main locations of the dominating species are indicated in the figure.
Panama
Figure 11 shows the fish distribution based on the information from the acoustic system.
As during the previous survey, the central part of the Gulf of Panama holds the lowest densities, while the highest concentrations are found at the edges, particularily in the north. Compared to high-productive areas on a world-scale, none of the registrations can be classified as "dense". In the north, the fish registrations consisted of mixtures of threadfin herring, bumper (Chloroscombrus orqueta) and grunts (Orthropristis sp.). These species are also dominating in the western part of the Gulf, but there at lower densities. South of the Pearl Island and towards the shelf edge, scads (Decapterus). butterfish (Peprilus) . dart squid, (Loliopsis diomedae) and round herring (Etrumeus teres) were dominating species. The fish fauna at the slope was made up of argentina , seabass (Centristhmus). cabezon shrimp (Heterocarpus vicarius), and a crustacean of no commercial value (Munida sp). The anchovy (Cetengraulis mysticetus), which was found during the previous survey, was not found in notable quantities during the last survey, and is probably distributed in the very shallow waters, inaccessable to the vessel. Westwards, at the narrow shelf between the gulfs of Panama and of Coiba, few acoustic registrations were made, but random bottom trawl hauls gave catches of snappers (Lutjanus) and mojarra (Diapterus).
In the gulfs of Coiba and Chiriqui, very scattered registrations of fish were made in the shallow waters. None of these acoustic registrations indicated density levels of interest for commercial fishing. The main species in this region were anchovy, threadfin herring, butterfish, and barracuda (Sphyraena).
Costa Rica .
Figure 12 shows the distribution of fish in Costa Rica, as observed by the acoustic system. The work carried out in Costa Rica suffers from serious limitations as sampling of the demersal fauna was not permitted in depths less than 100 meters. As most of the shelf off Costa Rica falls sharply into the deep from the 120m depth contour and almost all acoustic registrations of fish were located close to the seabed, virtually no sampling was possible. Therefore, nothing can be said about the composition of the fish fauna. Furthermore, the method of acoustic abundance estimation is dependent upon information on the size composition of the fish. With no length samples, the abundance estimates suffers from very low accuracy.
Figure 12 shows that most of the acoustic registrations were scattered. In the inner parts of Gulf of Nicoya and off Cape Judas however good registrations were made. Samples of the acoustic traces from these registrations are shown in Appendix 7. If these registrations represent commercial exploitable species or not remains to be investigated.
