Each year, large schools of mackerel hatch off Ireland’s west coast. As they grow, they travel north-eastwards and move into Scottish waters with little regard for the latest status of Brexit negotiations. There, both Irish and British fishermen catch them at maturity under EU fisheries rules.  If there is no agreement between the EU and the UK to replace these rules by the end of the current transition period on 31 December, Tánaiste and Minister for Foreign Affairs Simon Coveney said Irish fishermen will just catch the fish smaller, before they complete their migration, and everyone will lose.  A former…