It’s true; about 50 percent of the fish we eat are farmed. There is good reason for this as, one by one, the world’s commercial fisheries collapse through overfishing. According to FAO (2010), 70% of the world’s large commercial fisheries have either failed or are not far from it.
When things started to go wrong with world fisheries, fish farming was hailed as the ultimate solution. Fish could be produced cheaply and pressure removed from wild stocks. It seemed like the perfect solution to a very big problem.
Salmon are one of the world’s most desirable fishes and incredibly predictable in their behaviour. Eggs are laid at high altitude in clear freshwater mountain streams. After a stay of up to three years the young salmon move out to the sea to mature. Most are caught when they return to the same river they hatched in, which they find by following a remarkable olfactory memory.
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Early versions of fish farming followed an oceanic ranching model. Hatcheries produced salmon fry for release into rivers and allowed them to mature at sea. When the hatchery-produced salmon returned to spawn after 1-5 years at sea, they literally swam back into the factory that produced them, to become tomorrow’s fresh fish. Ocean ranching still goes on but has declined or in some cases been halted due to low return rates and, more recently, regulation.
Farmed salmon differ from ocean ranched salmon in that they are not allowed to mature at sea. Instead they are kept and fed in offshore cages guaranteeing a better return rate and rapid growth.
Official FAO statistics report that commercial wild salmon catches have remained fairly steady since 1990 at about one million tonnes per year. This is in contrast to farmed salmon which has increased in the same period from about 0.6 million tonnes to well over two million tonnes.
This farm production of salmon is incredibly efficient and incredibly profitable. However, as lead researcher Prof Matt Gage from the University of East Anglia’s School of Biological Sciences has said, “Around 95% of all salmon in existence are farmed, and domestication has made them very different to wild populations” (Yeates et al. 2014). Which means that farmed salmon have the potential to genetically swamp the wild stocks.
On the face of it this didn’t seem like a problem. Because salmon return to their original stream, each stream has its own genetic type or stock that has evolved to meet the specific conditions of that river system. Norway is home to the world’s most varied wild salmon stocks, with genetically distinct groups found in the country’s 452 different wild salmon rivers. But since 1971, Norwegian wild salmon stocks have diminished by roughly 80 per cent. Ten percent of that country’s salmon rivers have lost their populations entirely.
Explaining the crash of wild salmon populations
Back in 1971, aquaculture scientists started scouting 40 of Norway’s best wild salmon rivers to find the ultimate genetic combination for farming. These “designer” fish, selected for their ability to grow rapidly and use food efficiently, formed the breeding lines that by 2007 would, some 10 salmon generations later, support a US$3 billion Norwegian industry. Salmon farming had become a machine for printing money.
The future seemed to be bright. Salmon stocks were flourishing and hatcheries were producing well over 170 million “designer” salmon per year. But not all followed the rules. In 2007 alone, 450,000 Norwegian salmon escaped their destiny with the processing machines and this leakage of hatchery fish into wild stocks has been going on for 40 years. At the same time an estimated 470,000 wild Atlantic salmon were using the same rivers and breeding freely with the farmed strains.
In 2006, researchers Christian Roberge and Louis Bernatchez found evidence that farmed salmon had been evolving differently to wild stocks. These findings finally provided the necessary support for the suspicion that farm escapees could hybridize with wild fish and speed their decline (Roberge et al. 2006).
Many Norwegian rivers nowadays have as much as 50% hatchery salmon mixed into the returning catch. Because these hatchery fish are selected to grow faster, are aggressive, and are not as clever at avoiding predators as wild stocks, there is grave concern that interbreeding is reducing the fitness of wild salmon.
Jennifer Ford and Ransom Myers followed the survival of wild salmon in five regions around the world (Ford and Myers 2008). They found that exposure to hatchery-bred populations greatly reduced their success. Wild populations experienced a reduction in abundance of more than 50%, seriously compromising their stocks.
In 2008 US Secretary of Commerce Carlos M. Gutierrez declared a commercial fishery failure for the west coast salmon due to historically low numbers triggered by environmental conditions (National Oceanic and Atmospheric Administration, 2008). Hundreds of thousands of Chinook salmon (Oncorhynchus tshawytscha) typically return to the Sacramento River every year to spawn. At the time of the collapse, scientists estimate that fewer than 60,000 adult Chinook made it back to the Sacramento River. The fishery was closed until it could recover.
By 2012 and following the fishery failure, scientists had found that only about 10 percent of Chinook salmon spawning in California’s Mokelumne River were wild stock. The wild fish had been ‘over-run’ by hungrier and faster growing hatchery fish and were now heading for extinction. Published in the journal, PLoS ONE (Johnson, et al. 2012), the study said that there were no longer enough wild fish to maintain the population.
A 2009 report from Oregon State University researchers found that steelhead trout (a close relative of salmon) were now so genetically impaired that they were unable to reproduce enough to survive (see Araki et al 2007). It was only the huge hatchery output of young fish that kept ‘topping-up’ the stocks and giving the impression that all was well.
We have been flooding the rivers and oceans with voracious, fast growing fish that rob wild stocks of food and deplete their numbers. But the hatchery fish depend on us to make up for their weaknesses and inability to maintain their own abundance.
This is fine for making money. But the day we close down a hatchery the salmon in that river may be lost forever. They aren’t natural; like chickens, we have “designed” them and they can no longer exist without our continuing involvement.
There may one day be a solution. A project carried out at the Norwegian School of Veterinary Science and the Institute of Marine Research looked at the use of sterile salmon in aquaculture to prevent the disastrous interbreeding of hatchery salmon and wild salmon. By producing triploid fish for the farms, escapees are thought to be rendered sterile. But disappointingly for the project, researchers found deformities and reduced temperature tolerance made the fish less suitable for farming. This solution is not just around the corner.
And now what’s next for salmon?
The U.S. Food and Drug Administration (FDA) is reviewing the first genetically engineered (GE) animal for human consumption. And it’s a salmon. Produced by AquaBounty, this transgenic fish adds genetic material from a pacific Chinook salmon and an eelpout (Zoarces americanus) to cause Atlantic salmon to greatly overproduce its own growth hormones. The new fish will grow two to six times faster during winter than wild stock and be ready to harvest at an earlier age.
By November 2013, Canada had announced that it would support the export of AquaBounty’s GE eggs to Panama. The decision marked the first time any government had given the go-ahead to commercial scale production involving a GE food animal. The FDA has yet to rule on the GE fish.
To date AquaBounty has spent about $60 million trying to coax the FDA and public into accepting their product. Within the last year, supermarket chains including Whole Foods, Kroger, Safeway, Aldi, and Trader Joe’s have said they will not stock the GE salmon.
What we must keep in mind is that this animal has never existed before; it is new to the planet; we made it. We really have no idea of what it will do when we lift it off the ‘operating table’.
The FDA states that highly secure facilities will prevent GE salmon from escaping and affecting natural ecosystems. We are told that they won’t be able to breed because they are all going to be females; each and every one of them. The GE salmon will also be made infertile to prevent breeding with natural stock should some fish escape. (Actually it’s reportedly 99.7% infertile which means thousands of breeding fish out of the millions produced).
The future of the wild salmon stocks couldn’t be bleaker. Norway is losing half a million “designer” salmon a year from ‘secure’ farms, wild stocks in Europe and the US are collapsing, yet this new fish supposedly can’t escape and even if it does, none of the millions of fish AquaBounty produces will interbreed with wild fish.
Craig Altier, a member of the FDA’s Veterinary Medicine Advisory Committee and an associate professor at the College of Veterinary Medicine at Cornell University said, “We need to treat these (GE) fish as we would a potentially dangerous medicine or pharmaceutical, and apply all of the same security measures to its production and transport.” (1)
Fredrik Sundström (1 September, 2009) at the Department of Zoology, University of Gothenburg, Sweden says, “If transgenic fish become established in natural stocks they would be able to out-compete the natural breeds”. His work shows that AquaBounty fish would have a considerably greater impact on the natural environment than the hatchery-reared non-GE fish that are already wrecking havoc on wild stocks.
In itself, increasing the production of salmon is good for people and the economy. But it hasn’t so far been good for the environment. Because we have decided not to let nature do the ‘selecting’, the salmon we have been breeding are weak and dependent. They pose a real threat to the existence of some of the world’s most valuable fish. With the new AquaBounty GE salmon we will move further into uncharted waters; waters that soon may be filled only with salmon unable to exist without us.
(1) There are a number of other transgenic fish awaiting approval for commercial use including trout (Devlin RF et al. (2001)), tilapia (Rahman MA et al. (2001)), and zebrafish (Nebert DW et al. (2002)).
Araki H, Cooper B, Blouin MS (2007) Genetic effects of captive breeding cause a rapid, cumulative fitness decline in the wild. Science 318:100–103.
Devlin RF et al. (2001) “Growth of domesticated transgenic fish”. Nature 409, 781–782
FAO (2010) State of World Fisheries and Aquaculture (SOFIA) – SOFIA 2010. FAO Fisheries Department
Ford JS and Myers RA (2008) A global assessment of salmon aquaculture impacts on wild salmonids. PLoS Biol 6(2):e33.DOI:10.1371/journal.pbio.0060033
Johnson RC, et al. (2012). Managed Metapopulations: Do Salmon Hatchery ‘Sources’ Lead to In-River ‘Sinks’ in Conservation? PLoS ONE, 2012; 7 (2): e28880 DOI: 10.1371/journal.pone.0028880
National Oceanic and Atmospheric Administration (2 May, 2008). “Fishery failure declared for west coast salmon fishery.” Science Daily
Nebert DW et al. (2002) “Use of Reporter Genes and Vertebrate DNA Motifs in Transgenic Zebrafish as Sentinels for Assessing Aquatic Pollution”. Environmental Health Perspectives 110(1): A15 | January 2002 
Norwegian School of Veterinary Science (12 December, 2013). “Sterile salmon-reducing environmental impact of farm escapees.” Science Daily
Oregon State University (13 June 2009). “Hatchery Fish May Hurt Efforts To Sustain Wild Salmon Runs.” Science Daily.
Rahman MA et al. (2001) “Growth and nutritional trials on transgenic Nile tilapia containing an exogenous fish growth hormone gene”. Journal of Fish Biology 59(1):62–78
Roberge, C. Einum, H. Guderley, L. Bernatchez (2006) Rapid parallel evolutionary changes of gene transcription profiles in farmed Atlantic salmon. Molecular Ecology 15: 9–20
Yeates SE et al. (2014) Assessing risks of invasion through gamete performance: farm Atlantic salmon sperm and eggs show equivalence in function, fertility, compatibility and competitiveness to wild Atlantic salmon. Evolutionary Applications, DOI:10.1111/eva. 12148
University of Gothenburg (1 September 2009). “Risks Involved With Transgenic Fish.” ScienceDaily.