Fish swims to the same nest each year just like migrating birds

28 October 2016

Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world 

The ocean is a big place, but one small fish finds its way back to the same nest to tend to its eggs year after year.

This behaviour is reminiscent of migratory birds such as white storks or swallows. But unlike them, the fish does not migrate over long distances. Instead, it disappears for months on end from its rocky shore breeding sites along the western coasts of Europe and North Africa, travelling offshore to feed.

“The most interesting thing is that they get back to the same nest or to a very close one,” says Paulo Esteves Jorge at the Marine and Environmental Sciences Centre in Lisbon, Portugal. “It’s surprising to see in a non-migratory species standard behaviours of a migratory one.”

Male shannies (Lipophrys pholis) – which care for the eggs – were already known to return to their nests if they were artificially removed during their breeding season, from October to April. “Males show a great fidelity to the nest, being able to quickly return to it in the same year if they were taken away,” says Jorge.

The fresh finding that they return each year has emerged after the team tracked 211 of the fish over a three-year period using tiny electronic tags. “We believe that other similar species will have the same behavioural pattern,” says Jorge.

The team also conducted experiments in which they removed four fish from their nests and placed them more than 100 metres away, finding that half of them returned within two months.

Returning to breeding sites, much like sea turtles do, requires homing abilities, including well-developed navigation skills and an aptitude for keeping track of your position.

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