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Five snappy facts about Swedish crayfish

The Local · 19 Aug 2015, 07:26

Published: 19 Aug 2015 06:50 GMT+02:00
Updated: 19 Aug 2015 07:26 GMT+02:00

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Been invited to a crayfish party (kräftskiva)? If you're new to Sweden and need an introduction to this annual celebration, it's basically an excuse for friends and relatives to gorge on vast numbers of the freshwater crustaceans (which look like small lobsters and taste similar) washed down with snaps and some very loud drinking songs.
The tradition has been going on in the Nordics for centuries and evolved because the fish used to be a delicacy that could only legally be fished off Swedish shores during the late summer. These days you can buy imported crayfish year-round.
So, apart from being tasty, what exactly is so special about the spiky creatures that are worshipped across Sweden? Below are five facts to help you wow your Swedish hosts.

What crayfish look like after they have been cooked. Photo: Carolina Romare/Image Bank Sweden
1. They love the dark
Perhaps Swedes have a special bond with one of their favourite foods, because they both spend a lot of time living in dark, cold environments. Crayfish live in cool water and usually spend their days alone, sheltering beneath a rock or plant. They come out to forage for food when it gets dark, tearing apart just about anything they can catch with their large pincers including worms, insects, plants and molluscs.
2. Crayfish have blue blood
Like some snails, spiders and other crustaceans such as lobsters, crayfish have blue blood. This is because their blood has haemocyanin in it, a pigment which contains copper rather than iron (which is in haemoglobin which makes the blood of most animals and humans red). The animals breathe through feather-like gills.

A Swedish crayfish. Photo: Björn Tesch/Image Bank Sweden
3. They love to moult
Crayfish need to moult in order to grow. In other words when their shells get too tight, they need to shed them and get larger ones, a bit like children needing new clothes. The animals slide out of their old, hard shells when they get too big and emerge covered in a new soft and flexible shell. This allows them to grow for a brief period, before the shell becomes hard again, to help protect it against larger predators. Moulting occurs six to ten times during the first year of a crayfish's life.
4. Crayfish are part of an enormous family
There around 500 different species of crayfish, from tiny creatures that are just 2.5cm long to the largest kind, Astacopsis gouldi, which is found in the rivers of northern Tasmania and can weigh up to five kilograms. Crayfish can be blue, white or red. Red crayfish are most common. Swedish species are usually dark and turn red when boiled. So if your host offers you a blue one, chances are your host has made a rather large mistake with their recipe.
Story continues below…

A blue crayfish. Photo: Wikicommons
5. You can keep them as pets
Not sold on the idea of snacking on a food which has walking legs, sharp pincers and eyes are on movable stalks?  You could try keeping one of these fascinating creatures as a pet instead. All you need is a cold water aquarium with suitable aeration and filtration and some plants and rocks. Pet crayfish can be fed shrimp pellets as well as some types of green vegetables and supermarket-bought fish. But animal experts warn of putting two crayfish in a tank together because they may end up killing one another. Plus, crayfish can end up producing over 100 babies from a single hatch.

A pet crayfish. Photo: Wikicommons

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