Fish are cold-blooded animals and this property make them very efficient in terms of biomass accumulation. For this reason ecological trophic levels in aquatic systems can be more than terrestrial systems. Compared to fish, a warm-blooded cow is a furnace burning 90% of the food intake. Fish is a very valuable food. The global demand for seafood is so large that wild fisheries can’t meet that anymore. How are we going to feed fish to humanity?
Two-thirds of the salmon people eat comes from fish farms, which are commonly infested with parasites and diseases due to overcrowded conditions that increase transmission of pathogens. A native parasite known as salmon lice and a Salmon Leukemia Virus identified in 1992 and characterized in 1994 are the top two problem pathogens for farmed and wild salmon populations.
Sea lice are parasitic copepod related to shrimps, crabs and lobsters (crustaceans). Adult salmon can live with the lice. However many juvenile salmon cannot, including the pink salmon found in the Pacific from Japan to Siberia to California. The recurrent infestations of wild juvenile pink salmon have been shown to be associated with exposure of the wild fish to salmon farms. When the juvenile salmon enter the ocean, the first thing they encounter are salmon farms. Exposure to the sea lice when they’re far too small to be able to handle the parasite is a mortality sentence. It only takes 1 or 2 lice to kill a juvenile pink salmon. As a result, wild pink salmon populations are facing local extinction just north of Vancouver.
Salmon Leukemia Virus which is the main focus of this documentary has been shown to infect mature salmon before they enter their natal river to spawn.
Both sea lice and salmon leukemia virus affect natural salmon populations exactly the same way, by “being in their way”. Moving salmon farms away from the natural migration routes will greatly eliminate the rates of infections.
Currently fish food for salmon farms comes from wild harvested fish such as sardine or anchovy. Insects can be a very profitable food for these farms reducing the pressure on wild fish populations: