O-Fish-ial Fun Fact Thursday — 06 September 2018
Sep 6, 2018 · 2 min read
Hello, and welcome to O-Fish-ial Fun Fact Thursday. This month is weird fish sex month!!
Today we’ll be looking at the capelin, or for fancy people, Mallotus villosus.

How big does it get?
Capelins can get to 20cm in length, 50g in weight and 10 years of age.
Where can I find it?
In the very northern parts of the world, near Iceland, Alaska, Russia and Canada.
What does it eat?
Planktonic crustaceans.
What makes it interesting?
- They are highly migratory, moving huge distances for their size. They are permanently engaged in a feeding migration, chasing the plankton blooms as they occur. They also have a large spawning migration that is the basis of a huge food bonus to whales, seals and seabirds.
- Their spawning shoals can number in the billions.
- They spawn over sand or gravel at depths of 0–100m
- In the North European Atlantic, they spawn in the water, but off Newfoundland, they launch themselves out of the water and onto the shore. A huge number of them manage to beach themselves.

- Some capelin are offshore spawners though, which makes this species very confusing for ichthyologists.
- Making them even more confusing, some capelin populations are iteroparous for both sexes, some are facultatively semelparous and others display absolute semelparity.
- Iteroparous means a single fish can spawn multiple times over its lifetime. Facultative semelparity means that one of the sexes dies after spawning but the other sex is able to spawn over multiple seasons (in this case, the females survive to spawn again). Absolute semelparity means both sexes die after a single spawning season.
- For one fish to display all three spawning strategies is amazing.
- Capelin roe is very highly valued. It is mixed with wasabi or green food colouring and sold as wasabi caviar. It is also sometimes used as a substitute for flying fish caviar.
- Capelin themselves are sometimes used as a food fish, their taste resembling herring. More often, though, they are used in fishmeal.