Photo of farmed Norwegian salmon NatalieMaynor via flickr.
At TreeHugger we've had a lot to say about farmed fish - some good , but mainly negative. Farmed salmon, that perennial favorite (it's a $10 billion market as of 2007), causes native populations to crash, has higher levels of PCBs and other pollutants, and negatively impacts sustainable wild fish operation. In the last month a spate of articles has highlighted that farmed fish can also be fed the remains of other animals, including cows, and possibly even cows infected with bovine spongiform encephalitis (or 'mad cow'). While the link is a tenuous one, scientists think there is a potential for humans to contract the human illness Creutzfeld-Jakob by eating farmed fish fed byproducts from rendered cows.How do we get from mad cow to mad fish?
In the July issue of the Journal of Alzheimer's Disease, a neurologist suggests transmission of Creutzfeld-Jakob to people eating farmed fish fed BSE-diseased rendered cow parts is possible. In an article about the issue in Reuters, Dr. Robert P. Friedland said though he has not conclusively proved transmission, he wants the government to ban the feeding of rendered cow parts to farmed fish until further study is done.
In Friedland's magazine abstract he and his research group state:
"We are concerned that consumption of farmed fish may provide a means of transmission of infectious prions from cows with bovine spongiform encephalopathy to humans, causing variant Creutzfeldt Jakob disease."
How widespread is feeding farmed fish rendered meat products?
As you might have guessed, that's not such an easy question to answer. But 80% of seafood sold in the U.S. is imported, and as Consumer Reports notes, the U.S. doesn't have much of a system to make sure the imports meet the same regulations we have in the U.S. Consumer Reports points out that farmed salmon has already been show to have higher levels of PCBs, and dioxins, as well as possibly some unapproved pesticides and drugs accumulated in their flesh. But fish are generally supposed to be eating fish parts and fish oil.
However, some sources, including a report to the U.S. FDA's TSE (transmissable spongiform encephapathy) committee suggest that bone meal and blood meal from 'mammalian sources' have commonly been put into fish feed. In Canada, a 2007 law banned the use of so-called 'specified risk materials' such as the parts of cattle where BSE can be found, from animal feed. In the EU, the practice so spraying fish feed with dried cattle blood is also banned, precisely to avoid TSE risks. U.S. laws are not so specific, at least not yet.
So while the risks of getting Creutzfeld Jakob from farmed fish seems small and not yet proven, Friedland's concerns highlight a new problem with industrial aquaculture and reinforce the idea that finding wild-caught salmon is possibly a better choice. Intrepid researchers are also trying to come up with a way to feed carnivorous farmed fish algae and plants.
Read more about farmed fish at TreeHugger
10 Tasty Fish You Don't Want to Eat
Mark Bittman on the Future of Fish
Ocean Fish Farms Won't Save Fish and Can Easily Destroy Them
Farm Fishing Moves to the Condo
Finding a Sustainable Fish Stick