Dr. Ciaran Kelly:

One of the things about mackerel is that it is widely distributed. It is distributed all the way from the coast of Portugal right the way up to the coast of Norway. The Marine Institute has looked at this. A great scientist, Mr. John Molloy, was one of the people who looked back into the historical period, for example, the 1800s, when we saw see the exact same patterns of mackerel appearing and subsequently disappearing, particularly in the coastal area, which was a mystery at that point. Those are what we call juvenile mackerel, which are small and immature. Their distribution varies. They do not just live in a place like we do on a farm or in a house; they follow food. If there is little enough food available for them, depending on what they are hunting, they move into a different area. The distribution of mackerel the Deputy sees around the coast is just based on the distribution of food the mackerel are hunting. That is why they are there sometimes and not there other times. That can happen from one year to the next. Just because juvenile mackerel are not present in a bay in one particular year does not mean they are gone from the stock or gone from the bay. They are just gone from that bay for that year because they are in another bay.