Why go to all the trouble and expense to set up fish farms to harvest salmon? They build mesh pens out in coastal water, raise the fish in them, source and feed them food pellets, and the waste piles up on the seabed beneath them creating dead zones.
As an alternative, we stood at the entrance to a fish hatchery in Alaska and watched a hundred thousand free-swimming fish crowding the river waiting for their turn to swim up the fish ladder to where they were hatched and raised for the first few weeks of their lives, before they swam out to sea to feed, grow, mature, and swim right back to where they were raised, to present themselves.
Just harvest them! Are the financial and environmental costs worth it to farm fish in pens and take care of them all their lives while they pollute the water they’re living in, when all you have to do instead is hatch them, turn them loose, let them raise themselves in the open ocean, and return right to where they were released? Seems like a simpler cleaner way to me.
I want it to be that simple, but it’s not.
Say you want a hundred thousand adult fish to return. For that you might have to release ten million hatchlings. And a hundred thousand fish would not be nearly enough to satisfy the demands of even a single cannery. The combined canneries in Alaska alone can process a hundred million fish in a season, a combination of hatchery and wild. Releasing enough hatchery fish at a time to satisfy the demand could overwhelm the carrying capacity of the local estuary. Even when they go to live and grow in the open ocean, they don’t go to the entire ocean, they congregate at feeding grounds, competing with the wild fish stock and depleting the food source. Releases from multiple hatcheries from multiple countries could overwhelm the feeding grounds.
A local solution that seems simple, but it’s an illusion. A bigger picture to consider, and in this case a global one, with tradeoffs.