Figure 7 and 8 illustrates the distribution of all fish as observed with the acoustic integration system. This will mainly show the pelagic species, but some demersal fish which lifts off the bottom, especially at night will also be included. The units of acoustic reflection is 0.1 x m2/nm2 reflecting surface. This unit is not directly proportional to fish density since small sized fish gives a higher acoustic reflection per unit weight than bigger fish, but in gross terms the figures give a fair picture of the main distributional features of the pelagic fish in the area. An arbitrary scale has been used to illustrate different levels of concentration. The acoustic data will later be used for biomass estimates.
The Oriente.
The main feature to be noted in Figure 7 is the clear tendency for areas of high fish density to be located inshore and in the cool upwelled water masses in the easternmost parts, as can be seen by comparison with the surface temperature chart (Figure 3). High densities were observed along the coast in a narrow band from Cabo Tres Puntas westwards towards Isla Coche, southeast of Isla Margarita, in the bay outside Peninsula de Araya and in Golfo de Cariaco. The main contributor to these high densities was the sardinella. Dense schools were observed in this "fish area" both during day and night and they proved difficult to catch with pelagic trawl even at nigh time. One large and many smaller samples were however obtained and it seems clear that the schools were adult sardinella. In some areas juvenile sardinella was found together with anchovies in high densities e.g. offshore southeast of Testigos and east of the Margarita Island. Other species of sardines were also caught in the sardinella area, but in any quantities, only scaled herring Harengula jaguana. The catches in these areas also included some of the predators, barracudas, scombrids and hairtails in addition to demersal fish. The proportion in the catches can not, however, be directly taken as that existing in the sea since the trawls will exert a selection which depends on the size and types of fish.
Over most of the deeper parts of the shelf only scattered recordings were made indicating a general low level of fish density in mid water. The recordings usually consisted of traces of small schools or single fish not far off the bottom. Identification with bottom trawl showed that they should be attributed to Carangids, especially horse mackerel Trachurus lathami with some snappers and other demersal fish lifting off the bottom.
Western part, from Cabo Codera to Peninsula de Guajira.
In the western part the registrations of pelagic fish were generally more scattered, Figure 8. In the mouth of the Venezuela Gulf and outwards towards north of the Guajira peninsula aggregations of anchovies were located. Due to strong winds, especially when surveying the central parts of the mouth, the distribution of the anchovy might not be fully mapped. During strong winds and turbid sea, the surface waters, which also holds the main part of the anchovy, becomes saturated with airbubbles and blocks the soundpulses from the acoustic system. Southeast off Punto Fijo dense registrations, consisting mostly of thread-fin herring, was observed, and in the central part a concentration of anchovy and threadfin herring was located. Apart from this the gulf, and especially its inner parts, were lacking greater amounts of fish detected by the acoustic system. Off the Peninsula of Guajira , just off the shelf edge some young threadfin herring was detected, occurring together with meso-pelagic lantern fish at night. The fish resources off the peninsula were limited during the time of the survey.
