Estimation de l'abondance absolue des stocks de poisson pelagique dans les eaux tunisiennes

Abstract

In this paper the results of the quantitative acoustic survey of pelagic resources in Tunisian waters carried out in June/July 1973 are presented. A description of the direct calibration of the echo-integrator, using live fish, is given in detail. The absolute abundance of the total pelagic fish stocks present in Tunisian waters was measured as 580 000 metric tons. The average fish density over the whole area surveyed was estimated at 54 tons per square nautical mile or 15 . 7 g/m SUP-2 . By comparing the relative and absolute data obtained during the present survey, a conversion factor was obtained for each category of the relative abundance (very dense, dense, rare and very rare). This enabled the relative abundance indices obtained during the proceding echo surveys cruises carried out in 1972 and 1973 to be quantified. The absolute abundance of the main pelagic stocks was estimated by using the species composition of commercial catches in the Tunisian light fishery. A preliminary estimate of the potential yield of pelagic stocks in the coastal waters of Tunisia has been derived.