Few foods divide a dinner table like fermented fish. In Iceland, a cube of hákarl on a toothpick is a rite of passage for visitors and a quiet point of pride for older locals. Across the sea in Norway, plates of rakfisk are served every autumn with flatbread, onions and a glass of something strong.
The two traditions grew from the same problem: how to keep fish edible through a long northern winter without salt in plenty or a refrigerator. This guide looks at Iceland's fermented fish, what makes it smell the way it does, and how it compares with its Norwegian cousins.
Why Icelanders fermented fish
For most of Iceland's history, salt was expensive and hard to obtain, and firewood was scarce. Drying, souring in whey and fermenting were the practical ways to store food from one season to the next.
Fish was central to that diet. Cod and haddock were wind dried into hardfiskur, while shark and skate were left to ferment until they were safe and tender enough to eat. Hardfiskur is still sold today, eaten with butter as a snack.
Fermentation was not about flavour at first. It was a way to turn something hard or even harmful into food that could sit in a shed for months.
Hákarl: Iceland's famous fermented shark
Hákarl is made from Greenland shark, a slow, deep-water fish of the North Atlantic. Its fresh flesh is not safe to eat in quantity, because it contains high levels of urea and trimethylamine oxide, which the shark uses to cope with cold water and deep-sea pressure.
Traditionally, the shark was gutted and buried in gravel or sand, with stones on top to press the fluid out. Today it is usually fermented in containers. After several weeks, the meat is cut into strips and hung in an open drying shed for months, until a brown crust forms.
The result is cut into small cubes. The flavour has been described as cheesy, fishy and strongly ammoniac, with a chewy texture. Most first-timers remember the smell longer than the taste.
For a closer look at how it is made and served, read our full guide to hákarl, the fermented shark.
How to eat hákarl like a local
Hákarl is served in small pieces, not as a meal. Icelanders often eat it on a toothpick, followed by a shot of brennivín, the caraway-flavoured spirit sometimes called "black death".
The trick, say regulars, is to breathe out through your nose before you chew, rather than in. Chew a few times, swallow, and let the brennivín do its work.
You can find hákarl in supermarkets in Iceland, usually vacuum packed, and in some restaurants that serve traditional food. The Bjarnarhöfn farm on the Snæfellsnes peninsula is well known for producing it and shows visitors around its drying shed.
Kæst skata: fermented skate before Christmas
If hákarl is Iceland's best-known fermented fish, kæst skata is the most seasonal. Fermented skate is eaten on Þorláksmessa, the 23rd of December, the day before the main Christmas celebrations.
The custom is especially strong in the Westfjords and has spread across the country. Families and workplaces gather for skate lunches, and the smell of ammonia drifts through kitchens and stairwells.
The skate is usually boiled and served with potatoes, rúgbrauð rye bread and melted mutton fat or hamsatólg. Many Icelanders say the strong meal is a way to clear the palate before the rich Christmas food that follows. Our guide to Icelandic Christmas food covers the rest of the season.
What makes it smell so strong
The sharp smell of hákarl and kæst skata comes mostly from ammonia. Sharks and skates, like other cartilaginous fish, store urea in their tissues. As the flesh ferments, bacteria break the urea down, releasing ammonia.
That process is also what makes the shark edible. Fermentation and drying lower the levels of the compounds that make fresh Greenland shark harmful, and change the texture from tough to firm and chewy.
The smell clings to clothes and kitchens. Many Icelandic households boil skate outside or in a garage on Þorláksmessa to keep the smell out of the house.
Þorrablót and the fermented table
Fermented fish also appears at Þorrablót, the midwinter feast held in the old month of Þorri, from late January into February. The traditional spread, called þorramatur, gathers foods that were once a normal part of winter.
Next to hákarl you may find sour ram's testicles, singed sheep's head, blood sausage and liver sausage soured in whey. Not every guest eats everything, and that is part of the fun.
The Þorrablót revival began in the nineteenth century and grew in the twentieth, when restaurants in Reykjavík began serving þorramatur in wooden troughs. Today, the feast is held by clubs, schools, villages and families all over the country.
Hákarl usually sits on the edge of the table, cut small. It is rarely the most popular dish, but a Þorrablót without it would feel incomplete to many guests, especially older ones who grew up with it.
Norway's cousin: rakfisk
Norway has its own long tradition of fermented fish, and the best known is rakfisk. It is usually made from trout or char, salted lightly and left to ferment in brine for several months.
Rakfisk is especially linked with the inland valleys of eastern Norway. Valdres is one of its heartlands, and the town of Fagernes hosts a rakfisk festival every autumn that draws thousands of visitors.
The fish is eaten raw in thin slices, often on lefse or flatbread with red onion, sour cream and potatoes. Its smell is strong, but most people find it milder than hákarl.
In Valdres, the dish is tied to farms, lakes and family recipes handed down for generations. If you want to plan a trip around the festival, Valdresslekt's travel guide to Valdres covers Fagernes, hiking, skiing and cabins in the valley.
Lutefisk and surströmming: not quite the same
Lutefisk is often mentioned alongside these foods, but it is not fermented. It is dried fish, usually cod, soaked in water and lye until it swells into a soft, jelly-like texture, then rinsed and cooked.
Sweden's surströmming, by contrast, is fermented. Baltic herring is lightly salted and fermented in cans, which can bulge from the gas inside. It is famous for one of the strongest smells in the Nordic kitchen.
Together these dishes show how northern people across the region solved the same problem in different ways, depending on the fish they had and the salt they could get.
Why fermented fish still matters
Today, nobody needs to ferment shark to survive winter. Yet hákarl, kæst skata and rakfisk remain part of family gatherings and local festivals.
For many, the appeal lies in the link to the past. Eating these foods is a way to remember how grandparents and great-grandparents lived, and how much skill it took to make food last through the dark months.
Tips for trying fermented fish
Start small. A single cube of hákarl or a thin slice of rakfisk is enough for a first taste, and having bread, potatoes or a drink on hand helps.
Try it in context, at a Þorrablót, a skate lunch in December or a rakfisk festival, rather than straight from a packet. The mood of the meal changes the experience.
Finally, keep an open mind. Many people who grimace at the first bite come back for a second. For more context on Iceland's older dishes, see our traditional Icelandic food guide.
Cover image: "Hákarl (fermented shark)" by Austin Matherne, via Wikimedia Commons, licensed under CC BY 2.0.
About Sigrún Ólafsdóttir
Sigrún grew up baking rúgbrauð with her grandmother in Akureyri and has spent the last decade collecting recipes from kitchens all over Iceland. She writes Icelandic MAT's recipes, one dish at a time.