Conception, confection et essai d'un chalut pélagique à cordes parallèles pour une puissance de 500 chevaux vapeur

Abstract

This study bears on the design, manufacture and trials of a midwater parallel-ropes trawl. The fishing gear was designed for a 500 horse power trawler. It is made of four panels: equal top and bottom panels and two equal side panels. These latter panels are smaller in terms of dimensions. The trawl is also characterised by the substitution of the previous mesh with parallel ropes. Fishing experiments with this trawl were carried out in the north of Tunisian waters on board the research vessel Hannibal. During the trials, the optimal amount of sinkers floats and their distribution along the head rope and the footrope were conducted. Such setting promotes the catch of small pelagic fish moving towards the seabed to avoid the trawl especially during the day. These tests also establish the warps spinning coefficients according to the trawling speed and the depth of the footrope compared to the depth of the sea. The results indicate that the average of the horizontal and vertical openings of the trawl is 25 and 20 meters respectively. Furthermore, tests have shown that the trawl is efficient and suitable to catch small pelagic fishes. Moreover, yields of the trawl are important and composed more than 99% of pelagic species such as sardines and anchovies at depths beyond -80 meters without touching the seabed. This trawl seems to be adapted to the small pelagic fish in the North of the Tunisian water.