Big DFO lie and blunder, but in that case it was lies to keep the harvest of cod high to make a new cooperative fish plant be successful. That DFO scandal is well documented. All fish stocks, not just salmon, cycle as does the ocean productivity like those driven by the pacific decadal oscillation. Atlantic cod migrate and are top predators so are subject to the predator-prey cycles of most natural food chains.
Folks hate change and rationalizing things so we can avoid change or acknowledging it is a well documented behaviour/reaction. There is a lot more going on in the entire salmon ecosystem and life-cycle than can be explained by any of the natural cycles known to fisheries scientists and there isn’t a single “smoking gun” to blame.
Natural systems have a lot of built in resiliency, things we refer to as over abundance and redundancies. As such, fish and wildlife populations can be very resilient to a lot of change and it typically takes multiple factors in combination to elicit a significant change at the population scale. For e.g. intense fishing harvest in past decades was easily offset by high ocean productivity and ample freshwater habitat productivity. Currently I feel we’re finally seeing the effects of sustained unsustainable harvest, watershed scale freshwater habitat changes and loss, unsustainable ocean ranching, climate change effecting everything from freshwater stream temps, ocean temps and currents, freshwater hydrographs, ocean chemistry, species shifts and hosts of other changes we know and don’t know about. Eventually all natural ecosystems resiliency will be overcome if the host of impacts continue to stack up and persist for long periods. There are a lot more examples of this happening in recent history than just the Atlantic cod and there will be a lot more in our future as well.
That’s my view anyway.
Cheers!
Ukee