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 and represents an indicator of density of pelagic fish. An arbitrary scale has been used to illustrate different levels of concentration. The acoustic data will later be used for biomass estimates.
Over the larger offshore parts of the north and east coast shelf area only very scattered recordings were made indicating a general low level of pelagic fish density. Some aggregations were found inshore especially in the north. One should note that there are extensive inshore parts in the east which are too shallow to be reached by the vessel. The recordings usually consisted of traces of small schools or single fish not far off the bottom. Identification with bottom trawl showed that off the northern coast the recordings should be attributed to various species of Clupeids, mostly juvenile stages, anchovies and various predators, Carangids, horse mackerels, barracudas, sharks etc.
The highest densities of fish were located in the south over the Colombus Channel area where fish aggregations in schools and layers occurred over wide areas in some places with high densities. Some of these seemed to extend onto the shallow inshore parts of the shelf which could not be covered by the vessel. Trawl sampling and the characteristics of the echo traces showed that this was mostly small sized partly juvenile stages of Clupeids, scaled herring, thread herring, dogtooth herring and various anchovies mixed with small amounts of predators, barracudas, large sized hairtails and jack mackerels.
