Of the many weird and wonderful fish species in Irish waters, some are, well, a bit weirder and more wonderful than others. In no particular order, here’s a roundup of a favourite few of them.
Basking Shark (Cetorhinus maximus)
This is the Holy Grail when it comes to making your wildlife-loving buddies jealous (no, I’m not bitter about not having seen one yet, honest!). This is the second largest shark in the world, and can grow up to 12 metres long. But have no fear, these are gentle giants that are only interested in eating plankton which they strain from the water by swimming around with their mouths open. In an hour, they can filter up to 1.5 million litres of water through their gills! To stay buoyant they have a massive oily liver, and unfortunately they used to be hunted for this reason along the west coast of Ireland.
While no longer commercially hunted, they have been added to the IUCN Red List as a species that is at risk in Irish waters as they are still caught as by-catch (essentially meaning caught by accident) and have yet to fully recover from a past of being exploited.
If you want to be in with a chance of seeing one the season to do so runs from April to late July and early August, where they can be spotted from land and boats. Check out the IWDG website for sightings near you.
Conger Eel (Conger conger)
It may not have the most imaginative of scientific names but the conger eel is charismatic enough to make up for that. Divers often spot this eel peering out of its preferred hole or crevice, and it’s a fan of shipwrecks. It stays in its hiding place for most of the day, only emerging to feed at night, where it hunts for fish and crustaceans. It can tackle large crabs and lobsters, and when it does it often grabs the unfortunate animal and smashes it against a rock before devouring it. Charming. These fish can reach huge lengths, up to two or three metres long, and have very strong jaws, but they don’t tend to bite unless they’ve been provoked or frightened. Yet another reason for divers to keep their hands to themselves and for anglers to be cautious!
They have an interesting life history, where adults will migrate to deep waters in the Atlantic and Mediterranean to spawn, which they only do once before dying.
Ocean Sunfish (Mola mola)
Never mind Irish waters, this has got to be the strangest fish in any ocean. Looking rather like a fish a child started drawing then ran out of paper before getting to the tail, the sunfish spends its day hunting jellyfish, often in the depths, and as it gets cold down there it returns to bask at the surface, where it got its name. It also uses this time as an opportunity to rid itself of parasites, as it allows seabirds to remove any nasty hitchhikers it has collected. They can achieve massive sizes, up to three metres in height and 10,000 kg, making it the world’s largest bony fish. It’s also the most fecund, as females can produce 100 million eggs! An ridiculous yet loveable fish, 10/10 would recommend.
John Dory (Zeus faber)
This fish is not only tasty, it is a superb hunter. Its body is very thin, so seen head on it seems to almost disappear from view. When stalking its prey (sometimes even swimming upside down!), it sneakily manoeuvres close enough to use its secret weapon: a highly protrusible jaw. It can shoot its jaw out at high speeds, which create a suction effect that sucks up the unfortunate fish into the John Dory’s mouth. The striped markings along its sides can appear and disappear at will, and according to legend the black spot on its side is the fingerprint of St. Peter, preserved for posterity when he removed a coin to pay his tax from the fish’s mouth. We advise you not to try this at home.
Cuckoo Wrasse (Labrus mictus)
One of the most colourful fish in our waters, the cuckoo wrasse is beloved of divers for its appearance and its inquisitive behaviour, as it often swings right up to them, even admiring itself in their masks! Their reproductive behaviour is fascinating, as they start life as females (the pinkish ones with black and white patches on their backs) and change sex when they’re between seven and thirteen years old. However, to complicate things, some fish are born as males, but look like females. Known as primary males, as opposed to the usual secondary males, their reproductive role is not fully known.
Sex change in fish is relatively common, and is to do with their different breeding strategies. Fish that becomes males second tend to have a lot of mate and territory guarding in their courtship behaviour, so being a big, aggressive male is better for your genes, while fish species that become females second can produce more eggs as they are much bigger. Science!
Seahorses in Ireland? It’s more likely than you think! We have two species here, the short-snouted (Hippocampus hippocampus) and the spiny seahorse (H. guttulatus). The short-snouted can be found on rocky reefs, in harbours and on open sediment, while the spiny seahorse is generally only found in seagrass meadows. As the name suggests, the spiny seahorse has more spines, and the short-snouted seahorse has a shorter snout. Simple! Except for the fact that the short-snouted seahorse can sometimes grow long spines.
Like all seahorses and their pipefish relatives (which can also be found around our coasts), the males are the ones who become pregnant, and they can change colour. Unfortunately, they are under threat due to illegal trade and the destruction of their seagrass homes. They are also very sensitive to stress, so divers should check out The Seahorse Trust’s Code of Conduct.
Angel Shark (Squatina squatina)
Okay, okay, I lied when I said the basking shark is the Holy Grail of sightings to make your friends jealous, this is. The bottom-dwelling angel shark is nocturnal and an ambush predator meaning it sits and waits for its prey to venture within reach of it, when it lunges up to grab it. It can be found anywhere between 5 and 90 metres depth and is camouflaged to blend in with the sea floor.
Unfortunately, you are unlikely to ever seen one in Irish waters, and for a different reason. Like all sharks, the angel shark is slow to reproduce, and cannot recover quickly from fishing pressure. Measures were taken to protect the shark in 2005, but the population was already waning. The last known stronghold was Tralee Bay, and with the last confirmed sighting in 2015, there is a real possibility that this Critically Endangered fish has all but vanished from Ireland.