Figure 4 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 Figure 4 gives 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 4 is the clear tendency for areas of high fish density to be located inshore and comparing with Figure 2, in the cool upwelled water masses in the easternmost parts. The highest densities were found immediately west of the Dragons Mouth off the Paria Peninsula. This coincides with the lowest surface temperatures observed inshore. High densities were also observed in some patches along the coast westwards past Cabo Tres Puntas, southeast of Isla Margarita, in the bay outside Peninsula de Araya and in Golfo de Cariaco. The main contributor to the high densities in the easternmost parts was the sardinella, but mixed with anchovies further west and inshore. In some areas juvenile sardinella was found together with the anchovies. The catches in these areas also included some of the predators, barracudas and hairtails in addition to demersal fish.
A comparison with the distribution of small pelagic fish in the previous three surveys indicates that there may be a seasonal migration of large sized sardinella east - west along the coast with the easternmost distribution at about the time of the present survey and the westernmost around June.
Over most of the deeper parts of the shelf only scattered recordings were made indicating a 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, along the Tortuga Ridge especially horse mackerel Trachurus lathami with some mackerel, Scomber japonicus, snappers and other demersal fish lifting off the bottom.
Western part from Cabo Codera to Peninsula de Guajira.
As in the previous surveys hardly any pelagic fish was recorded along the narrow shelf from La Guaira westwards to the Gulf of Venezuela. In the Gulf itself some aggregations of small pelagics were located consisting of both thread herring and sardinella with some anchovy.
