Panama
Figure 7 illustrates the distribution of all fish as observed with the acoustic integration system. The unit of fish abundance is 0.1 m2per nm2 acoustic reflection. With further analysis these observations can be converted to biomass by weight. Fish that occur down to about 0.5 m from the bottom will be observable with this system.
A main conclusion from Figure 7 is that fish was not recorded even in scattered formation over the central offshore parts of the Gulf of Panama. The low catches with bottom trawl towards these parts confirms the overall low abundance here. Small pelagic schooling fish dominate the dense recordings found in the northeastern, northern and southwestern parts of the Panama Gulf. East of the Pearl Islands these consisted mainly of scads (Chloroscombrus and others) and thread herring. Catches in the dense area off Panama in the north were mainly anchovy (Cetengraulis), scads and sierra (Scomberomorus). The concentration in the southwest was mostly juvenile scads. Small sized squid (Loliolopsis) was present in many locations, but especially in the southeast. They give however little contribution to the 38 kHz echo sounder system, but show up on 120 kHz. This general picture of fish distribution in the Gulf may be related to outflows of rivers in the area, but it may also be significant that the central parts of the Gulf are covered with cool water with low oxygen content below about 50 m of depth.
In the Gulfs of Coiba and Chiriqui' the small patches of denser fish were also found over the inner parts. They consisted of scads, thread herring and anchovy. Scattered fish was found over wider parts of these western areas.
The extreme inshore distribution of some of these denser fish concentrations may have caused some underestimates, but the general features of the fish distribution in the area will not be affected by this.
Costa Rica .
Figure 8 demonstrates the distribution of all fish observed by the echo integration system. In scattered formation fish is found over wide parts of the shelf. No fish was recorded in Golfo Dulce and this is probably related to the oxygen deficiency in all but the surface water layer of this treshold gulf. Small schools were observed breaking the surface in parts of the Gulf, but these were not observed by sonar or echo sounder.
The scattered fish found over the Golfo Coronado shelf consisted of various Carangids, cutlassfish and bottom fish. The dense concentrations in the inner parts of Golfo Nicoya gave samples in bottom and mid water trawl of Carangids, such as lookdown, bumper and others, sierra, barracuda, anchovies, thread herring, snappers and other fish.
Off Cabo Velas silver smelts (Argentina) was recorded in a layer just off the bottom at abt 190 m of depth and the concentration of fish offshore west of Cabo Santa Helena yielded samples of cutlassfish, silver smelt and threadfin bass.
