Basking sharks are coming back to Ireland from April to August ! But do you really know who it is ?
Basking sharks are the second biggest shark species spotted in Ireland, after the Great White Shark (both are often confused). Most specimens regularly reach 7 to 8.5 m in length with some individuals reaching 9 to 11 m, which corresponds to the length of a double-checker bus.
They also have a triangular fin similar to the great white shark, hence its name in Irish : ‘Ainmhí Sheoil’ (“the beast with the sail”). However, they adopt a completely different lifestyle to their bigger cousins.
Indeed, what sets this fish apart is its feeding behaviour : filter-feeding. Basking sharks are able to filter near 1900L of saltwater per hour, to eat one of the smallest creatures of the ocean, plankton, and specifically, zooplankton (little crustaceans eating mostly seaweeds, which deviate by following the ocean currents).
We can spot them in Ireland near the surface during the spring / summer season thanks to the heat of the water, which is conducive to the creation of food-rich areas (plankton blooms). They are slow-moving sharks (feeding with their mouth wide-open at about 3.7 kilometres per hour) and giving us the impression they’re enjoying the sunshine. That is why we call this species “basking”. The rest of the year, basking sharks swim in warmer water, near the African coast for example. Nevertheless, we saw in the past few years that some specimens stayed in Ireland water even during winter.
Basking sharks have become an icon of the country but are classified as endangered by the International Union for Conservation of Nature (IUCN), in 2018. Recently, the Ireland government proposed to include the shark in the Wildlife Act, regulations to protect at-risk species. Even though they can live until they are 50 years old, basking sharks have a really long cycle of reproduction and could not survive without human intervention.
Formerly hunted for their meat, fins (still eaten in Asian countries) and liver (before electricity became common, people all around the world was heating their house with fish oil from basking sharks, which is still being produced today ), the species is still threatened by human activities, notably overfishing and habitat destruction, boat collision or entanglement in fishing gear.
Conversely, basking sharks are not dangerous at all for humans. They could be seen from boats or directly underwater without risks. Despite their lack of agression, it is important to respect them and avoid disturbing their lifecycle. Some organisations offer advice to help you make good choices.
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On boat : try to stay at least 100 meters away, and if the sharks are coming closer, turn off your motor. Don’t stay longer than 30 minutes and keep a constant speed of maximum 5 knots. (French Office for Biodiversity)
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For swimmers, divers, and watercraft handlers : stay grouped, with few people and in top water. Don’t try to touch the shark and keep at least a distance of 4 meters and avoid flash photographs (the irish basking shark group).
Although, basking sharks are still a mystery on several points for scientists : reproduction cycle, lifestyle during winter, behaviour in group, … If you see basking sharks during your stroll along the coast, don’t hesitate to take pictures and share your discoveries on baskingshark.ie, a specialized group studying this species in Ireland.
Sources and credits :
Who is the basking shark : https://en.wikipedia.org/wiki/Basking_shark
https://mwdw.net/species-basking-shark/
https://www.discoverwildlife.com/animal-facts/fish/facts-about-basking-sharks
Irish basking shark group : https://www.baskingshark.ie/
How to observe sharks without disturbing them : https://parc-marin-bassin-arcachon.fr/editorial/observer-les-mammiferes-marins-sans-les-deranger
https://fairseas.ie/2023/07/27/basking-sharks-ireland-shark-week/
Head Picture : © Irish Independent Website
Picture 2 : © Graham Campbell
Picture 3 : © Oxford Scientific/Getty
Picture 4 : © Simon Berrow