Do you like to make risky bets and ride a winning streak? That's not how salmon work.
Like a smart investor, Mother Nature prefers to spread her risk. For Bristol Bay salmon, there are many spawning rivers each with their own population of salmon that's a bit different than their neighbors. The net result? If one has a bad year because of a flood or drought, there are others nearby that might have a good year. The productivity of sockeye salmon in Bristol Bay is linked to within-species biodiversity.
It's the portfolio effect, and it's why biodiversity is good. Like a diverse investment portfolio, a diverse reproduction portfolio is good for fish and other animals.
And if you don't believe me, here's some science-y stuff that proves it (top right).
Sadly, we've undermined our salmon portolios in most places where salmon live, and now we're riding risky bets into winning (or losing) streaks. Remember the boom and bust for the Fraser River? Ouch.