Dr. Ciaran Byrne:

Warming of the seas is quite probably an issue as well. We have seen what we call grill fish, which are summer salmon, coming back at 2 lb, 3 lb and 4 lb. They are tiny fish, and it is obvious that they are not getting food at sea. There is a concern that where they are going at sea is not where the food is located. There are temporal issues as well because when a juvenile, which is a salmon smolt, goes out to sea, if it warms up too much in fresh water, it can smoltify earlier and miss its food cues and so on.