Fiskeforsøk med multifilament, monofilament, og monotwine nylongarn under lofotfisket i 1974

Abstract

From 6 February to 30 March 1974 during the spawning migration of Arcto-Norwegian cod a fishing experiment with gill nets of continuous-multifilament nylon, nylon monofilament and nylon monotwine was carried out in Lofoten. The different types of nets were combined to make up one gill net setting consisting of 40 to 92 single nets, half of which were multifilament nets and one quarter each monofilament and monotwine nets. The sequence of the single nets was varied during the experiment. The result for the total experiment was that the monofilament nets caught 26 %(in numbers) more cod than the multifilament nets and 38 % more than the monotwine nets. For saithe the monotwine nets were the most and the multifilament nets the least efficient. The average length of the captured fish was slightly higher for the multifilament than the monofilament nets whereas the fish caught by the monotwine nets were somewhat smaller. Taking the length frequency of cod caught by purse seine in the same area during the same time as representative for the cod available to the gill nets, a selection curve for each of the three gill net types was calculated. The length frequency of the cod in the purse seine catches showed that the mesh size used in the gill nets (186 mm) was clearly to small. 0n the basis of the selection curves the theoretical catch with optimum mesh size fir the three types of gill nets was calculated. The results indicated that the catches of the monofilament and monotwine gill nets would be approximately equal and about 45% (by weight) higher then for the multifilament gill nets.