Carcass - The hypothesis you outline rests on the concept that maturity in Pacific salmon/steelhead is related to the amount of time spent in the ocean, rather than achieving a specific body size.

If achieving maturity is time-dependent, and food is limited, they would exhibit lower body size at maturity, which is what we’re seeing, and which you have articulated.

However, if Pacific salmon depend on achieving a specific body size before they mature, their maturity would be delayed rather than being stunted.

The problem with delayed maturity is the probability of additional mortality from either fishing (troll fishery) or predation (orca). So the effect would be indirect. That is, if maturity is delayed, the fish need to spend more time in the ocean which means they are subject to additional mortality (predation/fishing). That means the only fish returning are those that don’t spend much time in the ocean. The returns would be composed primarily of smaller, younger adults because the older, larger fish don’t survive long enough to spawn. After all, nobody throws back a 30lb Chinook hoping it will grow to 50lbs, even though it might.

Either way, the result is the same – lower size at maturity, albeit indirectly, in this case.

I’m not saying your hypothesis is incorrect. I’m just saying there’s another way of explaining what we’re seeing.