Escaped Farmed Salmon Caught in an Icelandic River
By Kjartan Þorbjörnsson
Posted December 6, 2018
Escaped farm salmon showing up in Icelandic rivers.
Today Matís, a government-owned, non-profit, independent research company, confirmed by DNA testing that two salmon recently caught in Fífustaðadalsá river in Arnarfjörður fjord were farmed salmon of a Norwegian origin. The fjord is where Iceland’s largest salmon farming company, Arnarlax, keeps their open sea pens and earlier this year, a considerable number of farmed salmon of Norwegian origin escaped their pens. The exact number of the escaped fish couldn’t be established. The salmon caught in the small Fífustaðadalsá were female and ready to spawn, which could have had devastating consequences for the wild salmon stock in the river.
Female fish about to spawn
Biologist Jóhannes Sturlaugsson has been monitoring fish stocks of three small rivers in Ketildalir valley by Arnarfjörður fjord for four years. The wild stocks in these rivers are very small, which makes it easy to spot any changes. Jóhannes caught every fish in the Fífustaðadalsá river with dip nets, measured, and tagged them, before releasing them. The native spawning stock consisted of twenty salmon and their spawning season was almost over. But in the river, they also caught the two large female fish that looked markedly different. They had large wounds caused by salmon lice, damaged fins and gill flaps, and torn tails: typical characteristics of farmed salmon. Their origin was later confirmed by DNA tests.
“Four farmed salmon have been caught in Icelandic fishing rivers this year. These two make for a marked increase and they are the first confirmed examples of mature farmed salmon about to spawn in an Icelandic river. I think we caught them in the eleventh hour. One would have spawned in a matter of hours and the other in a few days,” Jóhannes says.
Native wild salmon under threat
Asked about what’s at stake if farmed salmon spawn in an Icelandic river, Jóhannes points to Norway as an example. Wild Norwegian salmon is struggling, even though their farmed salmon is a Norwegian stock. “Each river has a special stock of salmon, that has adapted to the environment and evolved for thousands of years, each stock differing slightly in when it migrates to the sea, how long it stays there, how it spawns, how it’s built to jump waterfalls and so on. When you mix foreign DNA into the gene pool the damage is done. The adaptation might disappear, and the worst-case scenario is that the stock goes extinct.”
Jóhannes says there’s even more risk involved. “Farmed salmon spawns later than wild salmon and when doing so can dig up their eggs and replace them with its own, destroying the eggs laid out earlier by native salmon.”