THE TRAWL SURVEY

During the survey 52 trawl hauls were carried out of which 37 were with bottom trawl and 15 with pelagic trawl. Of the bottom trawl hauls all except two were selected by random location and thus forms a series of data which may be used to estimate the density of fish by the so called “swept area method”. Assuming that all fish within the wings of the bottom trawl were caught, the following estimates by location strata were obtained.

	Ras al Hadd-Masira	Masira Bank	Sauqara & Kuria Muria
Number of fully completed hauls	9	9	15
Mean total catch (kg/hour)	1070	393	679
Estimated density (tonnes/nm)	36	13	23
Shelf area 0-200 m (nm2 squared)	2800	3500	5850
Estimated biomass (thousand tonnes)	100	45	135

In the above figures the small pelagic clupeids and carangids have been excluded from the catches when present and the estimates thus represent the “non-pelagic” species.

As the trawl based estimate includes the whole shelf in the calculations, whereas the acoustic estimate omits some shallow unsurveyed parts of the shelf, the two demersal fish estimates of 235 and 280 thousand tonnes respectively seems to be in fair agreement.