The vessel is equipped with Simrad EK400 echosounders and Simrad QD integrator. This system was used to record the distribution and abundance of small pelagic fish and of demersal fish down to 200 m depth. A 38 kHz system was used for abundance estimation, while a 120 kHz system was utilized only as an additional aid in identification and interpretation of the echo traces.
The output from the integrator is expressed in millimeters on graph paper and represents indices of abundance of fish and plankton. The integrator output is separated into plankton and fish according to the characteristics of the echo traces and the trawl samples.
Figure 2 shows the distribution of pelagic fish during the present survey. Three levels of fish density are given; very scattered (1-10 mm), scattered (11-50 mm) and aggregated (51-100 mm). In areas with high productivity two more levels are frequently used: dense (51-100 mm), and very dense (>100 mm). Such densities were not found during this survey.
Figure 2. The distribution of small pelagic fish.
The biomass of small pelagic fish on the shelf was assessed to 56 thousand tonnes. The small pelagic resources consisted mainly of anchovy (Engraulis encrasicholus) and pilchard (Sardina pilchardus) Mean lengths from samples were in the range 8-10.5 cm.
Aggregations of demersal fish were not recorded at all by the acoustic system. In the 8 bottom trawl hauls only small sized fish were present. The catches in the bottom trawl ranged from 2 to 45 kg/hour, excluding anchovy and pilchard. The mean catch was 20 kg/hour. Records of the catches are shown in Appendix 1.
The general impression from the short survey is that the area investigated seems to be heavily overfished. This confirms the results of an Italian trawl survey which took place last year. The Nile Delta does not seem able to sustain a spawning stock of commercially valuable fishes as seabreams and groupers, only small juveniles are present and in small numbers. It is likely that these juveniles descend from spawners in the vicinity of the river delta where the bottom is too rough for trawling.
Only very strict regulations will enable reestablishment of a balanced fish fauna in the area.
