Increasing soak time improves size selection and harvesting patterns in common whelk ( Buccinum undatum ) pot fisheries

Common whelk is a neo-gastropod that is intensively fished on the west and east temperate Atlantic with baited pots. The UK hosts the largest Whelk fishery contributing 10–15% to the national Shellfish landings, worth 15–27 million £ a year. The fishery is regulated by a minimum conservation reference size (MCRS) which for most areas is set at 45 mm total shell length. However, scientific information quantifying the size selectivity for pots to catch common whelk and to what extent soak time applied affects it is limited leaving it unknown to what extent the existing fishing practice obtains a size selection that matches the MCRS. Therefore, experimental fishing trials were conducted to fill this knowledge gap. The results obtained demonstrated that soak time significantly affected the size selectivity for the pots. Specifically, it was found that only 75% of the whelks would be size sorted if soaking time for the pots was as short as 18h while with an extended soaking time to 46h practically all (97%) whelks entering were size selected by the escape gaps in the pots. Therefore, soaking time needs to be considered to obtain an efficient size selection at the seabed.