Sink or Swim - The Life and Times of Freshwater Fish Skip to content

Sink or Swim

The Life and Times of Freshwater Fish

Words by
Kjartan Þorbjörnsson

Photography by

“Some things in nature simply inspire an emotional response. The Þingvallavatn lake brown trout is one of these phenomena. It’s a fantastical, mythical creature,” says biologist Jóhannes Sturlaugsson.
“Some things in nature simply inspire an emotional response. The Þingvallavatn lake brown trout is one of these phenomena. It’s a fantastical, mythical creature,” says biologist Jóhannes Sturlaugsson. For the last two decades, he has studied the brown trout stock in the lake, unique in Iceland and even the world. Trout numbers in the lake are up, after years of decline.

Big fish

At 84km2 (32mi2), Þingvallavatn is Iceland’s largest natural lake. lt lies in a rift valley between two tectonic plates, the Eurasian plate and the North American. Most of the water comes from springs at the bottom of the lake. The rivers that do run into it are not large, the most well-known is Öxnará. Each autumn in October and stretching into November, the lower end of the small river fills up with giant brown trout who swim up from the depths of the lake to spawn. That’s where Jóhannes catches, measures, and weighs them before releasing them back into the river. Several of the fish he has seen many times before. When Iceland Review met up with Jóhannes, the temperatures had dropped below freezing and the caged fish he had already caught were underneath the ice. According to Jóhannes the brown trout in the lake was originally anadromous and colonised the lake following the end of the last ice age. Some 9,000 years ago, when the ice cap melted the land rose, the fish were cut off from their feeding grounds in the sea by impassable waterfalls. Luckily, some anadromous arctic char was also stuck in the lake at the same time and thrived there, the perfect nourishment for the trout to grow large and populate the water. “Þingvallavatn and its unique underwater ecosystem is so large and diverse that it offers the perfect conditions for this king of Icelandic freshwater fish, larger by far than any other in the country.” brown trout Þingvellir

Underwater adventures

Jóhannes breaks through the ice by the cage, prepares his measuring equipment and captures a 9-kilogram (20-pound) male trout from the cage. On its side is a deep cut from repeated biting of other males fighting over females at the spawning grounds. “They are incredibly hardy and strong: he’ll be healed in early summer,” says Jóhannes, as he documents its measurements, takes a scale sample, and fits it with a tag in order to recognise it when they meet again. The research has made it possible for him to study the trout’s behavioural patterns with the help of electronic tags. The trout usually reach an old age, so they tend to have some adventures through the years. “Everything you, as a scientist, would hope the trout is doing, it does.  It dives from the surface to the bottom of the lake for an adventure and some thumb their noses at the winter cold by skipping hibernation, keeping its metabolism running and heating up by finding sources of warm spring water.” In most Icelandic lakes, fish need to spend 24 hours a day eating during the summer months to be able to survive winter, but in Þingvallavatn, there’s enough to eat all year round. The trout in the lake also reach maturity later than most, often at six or seven years of age. Until that point, they grow quickly, as no energy is spent spawning. “Another thing is its long life. After it hits puberty, it can still grow. The oldest trout I’m currently observing is 17 years old,” Jóhannes tells me as he releases the fish through a hole in the ice. The heaviest fish Jóhannes has handled was a 12.7-kilogram (28-pound) female fish. “I was lucky enough to get her electronically tagged, so I could watch her movements for two years after that.” He says the longest fish can reach 110cm (43in), but they rarely grow over one metre. brown trout Þingvellir

Making a comeback

Despite their hardiness, Þingvallavatn trout were recently in danger of extinction. The main spawning grounds of the brown trout were almost wiped out when the river that runs from the lake, Efra-Sog, was harnessed for electricity production in 1959. The stocks that survived were either overfished or suffering from the change of environment.  In recent years, the biggest spawning stocks have muultiplied rapidly and now well over 2,000 trout spawn in the rivers Öxará and Ölfusvatsná. It also helped that the catch-and-release method grew more popular with anglers. “Luckily, people can battle the brown trout without killing it. The lake has several stocks of the trout and all of them were looking pretty rough at the end of last century. People were talking about it in the past tense.” Since the turn of the century to this day, actions have been taken to save the trout that have proven successful. Jóhannes doesn’t mind that anglers fish for the huge trout, as long as they release them afterwards, as the hardy fish generally is not harmed. “I’ve tagged fish that have later been caught several times over by fly fishermen. I’ve even caught the same fish again repeatedly when they come in to spawn year after year.”  
Salmon farming Iceland
Aquaculture in Iceland
Aquaculture in Iceland

Catching intruders

Jóhannes’ efforts and research have been instrumental in keeping the brown trout happy and healthy but his mind is elsewhere these days – on wild salmon. “I’m embarrassed for not talking about it more publicly until now,” he says. “There’s only a handful of us doing this type of research but we should all be speaking up. Wild salmon is the biggest treasure of freshwater in Iceland and we are putting it in grave danger.” The threat stems from extensive salmon farming by the coast of Iceland. “How is it that we, with our unique wild salmon stocks, are confident enough to import fertile farmed salmon of Norwegian origin and rear them in open-net sea pens, while we forbid importing foreign breeds of cattle or horses? Those are animals that we can contain while salmon is kept in open pens and can always escape into nature, as recent history has shown.” 

Four years ago, Jóhannes started monitoring the fish stocks of three small rivers in Ketildalir valley by Arnarfjörður fjord, armed with decades of scientific experience and in co-operation with landowners. The fjord is home to the biggest fish farms in Iceland. The wild stocks in these rivers are very small, which makes it easy to spot any changes. Earlier this year, a considerable number of farmed salmon escaped their pens in Arnarfjörður. The exact number of the escaped fish couldn’t be established. Iceland Review joined Jóhannes on his trip west to monitor the conditions in one of the rivers. One autumn night in late October, Jóhannes and his helper caught every fish in the 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 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. “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, clearly distressed.

Salmon farming Iceland

Rivers at risk

But 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 will be damaged and the worst-case scenario is that the stock goes extinct. Still, we accept farming a number of in numbers multiple times over all the wild salmon in Iceland without hesitation, knowing that these fish tend to escape.” 

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. We think we’re so exact when it comes to our actions in nature but we’re not consistent. We have a history that we don’t want to repeat,” Jóhannes says, referring to the case of mink importation in the early 20th century. “It’s the only example I can think of where no one has stepped up and apologised for the mistakes that were made.” Minks were imported in 1931 and only a year later, the first ones escaped. Since then, the mink has wreaked havoc in nature and proven impossible to keep under control. “We know we have to do better if we do not want to risk Icelandic salmon stocks. An official apology by some politician decades later will not help Icelandic salmon. It’s not a question of not caring about people in the countryside and their employment. Somebody needs to speak up for the salmon. Someone has to talk about what people are only dimly aware of. We know that salmon is in danger and we have to act accordingly.”

Icelandic salmon
Icelandic salmon

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