Yes, this is referring to this idea that there are fish that support a fishery or that you fish, and then there are fish that are essentially not part of that. There are fish that are considered to be irrelevant.
This is what I was mentioning earlier about the concern around this. If you go to an ecologist and say, “I want you to prove to me that this fish doesn't matter”, you would find that's a really hard thing to do. At the same time, it's also hard to prove that this particular fish matters, because if you were to remove a fish from an ecosystem, the fish isn't just going to keel over, it's going to try to eat something else.
This is what we see right now with Atlantic cod—a good example. There is some concern that we're finding some localized groups of cod that don't have bellies full of fish. They have bellies full of sea stars and other species that might be suboptimal for them to eat. So, it's not that you flip a switch and everything falls apart overnight. It's that you're taking out the Jenga pieces and making the whole tower a little flimsier and increasing the probability that you're going to get it to fall over at some point.