Haul duration experimental data set (0 & 30 minutes hauls)

In 2003 two experiments were carried out in the Bay of Biscay to compare catch numbers obtained in standard research 30-min hauls with those from 0-min hauls to determine the so called end effect. The end effect in trawl catches is defined as the proportion of the fish catch taken during shooting and hauling of the net, a period excluded from what is nominally referred to as haul duration. In 0-hauls the trawl was hauled as soon as the trawl geometry stabilized on the seabed. The trawl used was a beam trawl rigged as twin trawl. Overall 24 hauls were carried out, six 30-min and 18 0-min hauls. Average catch ratios (0-min/30-min hauls) ranged from 0.05 (s.d. 0.06) for sole to 0.34 (s.d. 0.64) for hake.