The economic hot-button issue when it comes to sovereignty - either in an independent Scotland or in the UK, independent of the European Union. The core of the problem is that fish don't understand international borders and swim all over the place. The result is that management of fisheries in any area requires cooperation between countries. Unilateral action is simply not possible as the United Kingdom found out in the Cod Wars with Iceland in which the Royal Navy lost. The feeling among fisherman is that there are plenty of fish and that regulations are getting in the way of making money. The need for sustainable fishing and closing areas for conservation is simply lost on quite a few who still think that a return to the free-for-all of the early and mid 20th century is possible if only those fisheries scientists would shut up.