Can farmed fish save their wild counterparts? It’s an argument I’ve heard a couple times in favor of farming certain species that are under pressure in the wild.
Now researchers are claiming farms will help bluefin tuna. The species was in the news earlier this week after the Mexican government suddenly banned all bluefin tuna fishing for the rest of 2014. The ban came after WWF warned that Pacific tuna fishing catches should be cut in half to guarantee sustainability, claiming that the species had declined 96 percent and that 90 percent of the catch were juveniles that had not yet had the chance to reproduce.
Bluefin has long been at the center of sustainability efforts. In the Atlantic, overfishing in the Mediterranean and Eastern Atlantic led to steep declines in the 1990s and early 2000s. International conservation measures have helped stocks recover (so long as all nations follow those measures). Now Pew is calling for similar international action to save Pacific stocks, including science-based catch limits, minimum sizes and an oceanwide rebuilding plan.
No environmental group seems to be promoting farming as the answer. Yet researchers for an EU-funded project are hoping to establish a sustainable and commercially viable operation raising bluefin tuna. Because the researchers are focusing on hatching the fish (like they do in Japan), it’s at least more sustainable than current Mediterranean methods of catching juveniles and raising them until they are fat enough for market.
But can farmed bluefin ever really be sustainable?
The researchers admit there are challenges. In confinement, adult bluefin have been known to cannibalize juvenile fish. Ocean-crossing bluefin are also fast swimmers with poor eyesight. They bash into the walls of their pens if they are farmed in closed tanks on land. (I know this is not the point of sustainability, but it’s also heartbreaking to imagine these great fish in this type of environment.) But farms risk contaminating the waters if they are in the open ocean.
Then there’s the issue of what they eat. Though vegetarian feed is more sustainable, tuna grow faster and bigger when there’s dead fish in the feed. That puts pressure on the wild forage fish stocks that go in the fishmeal. So much for preserving wild populations.
Bruce Collette, senior NOAA scientist and chair of the tuna and billfish group for International Union for Conservation of Nature, told Science 2.0 that he did not believe bluefin will be successfully domesticated.
“The best course of action for the bluefin is to reduce the quotas to let the wild populations increase to some approximation of their original size,” he said.
As fish farming grows in popularity it’s important to acknowledge that some species just don’t lend themselves to it. Tilapia can be raised pretty much anywhere you can put a pond. A bluefin needs an ocean.