A strange visitor to Kerry’s coast

A STRANGE-LOOKING fish, caught off the south-west coast last summer, has been tracked to the Bay of Biscay.

Scientists believe warmer waters in the north Atlantic may be attracting these ocean sunfish which look like they are all head and no tail.

The sunfish netted off the Dingle peninsula by a UCC-based research team was tagged with satellite-linked equipment which recorded information that may yet unravel some of the mystery of this denizen of the deep.

It was the first time a sunfish — a species about which little is known — was tagged in Irish or British waters. All the time, the seas off Dingle continue to throw up species of fish that are more frequently found in temperate waters. Some of the better specimens end up in the Dingle Oceanworld aquarium.

One of the UCC research scientists, Dr Tom Doyle, said the research could have important implications for Ireland, as sunfish may represent a good biological indicator of climate change.

If sunfish sightings increased dramatically, it could be a clear sign that our waters were warming and the climate changing, he added.

“Sea temperatures have increased in the last 10 years and last year was quite warm. We’re likely to see more of these fish if waters get warmer. We’re still analysing data from the tagged fish,” said Dr Doyle, of UCC’s Coastal and Marine Resources Centre.

An area off the Kerry coast between Smerwick Harbour and Brandon, on the northern side of the Dingle Peninsula, attracted large numbers of sunfish last summer.

Dr Doyle and his colleagues used a cast net to catch two sunfish during their Kerry study. They brought them onto a boat provided by Padraig Frank Ó Súilleabháin, of Eco Tours, Ballydavid, and placed them in a big tank so the fish would not be stressed while being measured.

The research team used techniques that were developed last year in the same waters to tag leatherback turtles that also feed on jellyfish.

The project is part of broader research being conducted in collaboration with universities in Plymouth and Swansea. Dr Jon Houghton, of University of Wales, in Swansea, remarked: “The northern coast of Dingle represents an important habitat for sunfish and provides a fantastic opportunity to study these ocean giants.”

It was not known previously how many sunfish were in these waters, but the researchers now believe the Dingle coastline may hold significant numbers of sunfish, with up to 20 individuals observed in a day.

Why so many sunfish gather in this small area is unclear, but a strong possibility is that the northern coastline of Dingle is a nursery ground for sunfish, where juveniles can shoal and feed together.

“They feed largely on jellyfish and a superabundance of jellyfish is an obvious reason for them to be there,” Dr Doyle maintained.

As this diet is nutritionally poor, they consume large amounts in order to develop and maintain their great size.

Similar nursery grounds are known in Bali, Indonesia, and off the coast of California. Sunfish are the largest bony fish in the world and can grow up to three metres in length from their tip, or mouth, back to their tail fin. They can weigh up to two tonnes.

They are related to puffer fish and porcupine fish and are believed to swim as deep as 600-700 metres. However, they can also spend a lot of time at the surface of the water, with their large dorsal fins flapping from side to side.

They have a unique shape that is flattened from side to side and stretched from top to bottom. Their body is shortened to such an extent that they are literally all head and no body. Their German name ‘Schwimmender kopf’ means ‘swimming head’.

Amazingly, females can produce up to 300 million eggs, the largest number of eggs ever recorded in any fish. But almost nothing is known about their movements and behaviour.

Adult sunfish are vulnerable to few natural predators, but sea lions and sharks consume them. Sunfish are considered a delicacy in some parts of the world, including Japan and Taiwan, but sale of their flesh is banned in the EU.

Sunfish are frequently caught in gillnets, and are also vulnerable to harm from encounters with floating rubbish, such as plastic bags.

Huge sunfish have been known to collide with ships. In one incident, in Sydney, a 1,400kg individual got stuck in the bow of a cement vessel, causing its speed to slow from 14 to 11 knots. The skin of this sunfish was so rough it wore the ship’s paint work back to the bare metal.