Let me speak to this very concisely. I've been involved in a collaborative project looking at the size of Alaska salmon of all the species we had information on from across all the state—over 12 million individual records of size of salmon—and all salmon across the species that we have information on have declined in size. Chinook salmon in particular have gotten smaller. All the salmon have gotten smaller, especially after about the year 2010. That year was a real changing point for sizes. Things were kind of going up and down, but there was a precipitous decline in size.
The answer to your question is that it is not that fish are just maturing younger. The older fish are being lost and are not surviving. As fish grow, they potentially could just be growing faster, or maybe there's more food, and they could mature younger. But that is not what is happening. There's been a change in age structure that is likely tied to a change in genetics.
The ocean seems like it is increasingly dangerous. Fish that are programmed to spend a lot of time in the ocean are not surviving. We are losing those genes.