Two Basking Fish of the West Highland summer

Roddy Maclean shares his enthusiasm for two amazing summer visitors to our waters

Leugh ann an Gàidhlig

In the west of Ireland, there are two remarkable marine fish that bask under the name of ‘sunfish’ or their equivalents in Irish Gaelic – iasc gréine or similar, the name involving grian ‘sun’ in its genitive form gréine. I have used the term ‘bask’ advisedly, as both species, while completely unrelated except insofar as they are both fish, are to be encountered swimming slowly and deliberately at the surface of the sea, as if they are basking in the sunshine. For this particular blogger and Scottish west-coast sailor, a close encounter with one, or preferably both, makes for a wonderful and complete maritime summer!

Scottish mariners are familiar with the very same species in our own waters during the summer months, but in Gaelic Scotland it is generally only one of them that is referred to (with subtly different spelling from the Irish) as iasg-grèine – the sunfish (Mola mola), one of the world’s largest bony fish which shares its name, in translated form, with that used by English-speakers. The other species is a cartilaginous shark – the second biggest fish in the world – sometimes known here as a ‘sailfish’ because of its large dorsal fin which is reminiscent of a dark sail slowly making its way across the water.

A basking shark feeding – as seen from a boat, with the Isle of Coll in the distant background. This specimen was over 5 metres long. Photo © Roddy Maclean

As well as iasc gréine, the basking shark (Cetorhinus maximus) is quite commonly referred to as a liabhán gréine ‘leviathan of the sun’ in Irish Gaelic. In Scotland it is usually a cearban (or the variants carban and cairbhean), a word whose etymology is unclear. One Scottish dictionary gives the basking shark the name cearban-grèine, maintaining the solar connection to the species in our own terminology.

The basking shark is one of only three plankton-eating shark species, and defers only to the whale shark in size, generally reaching up to 8m in length (the largest ever recorded was a whopping 12m). A gentle leviathan, it is found in all the temperate oceans of the world and is migratory, visiting Scottish waters in the summer months. During the winter it dives to depths of as much as 900m.

It is truly a monster, but of mild disposition and poses no danger to humans, unless it happens to upset a small boat or kayak with a flick of its tail. The cearban can often be seen swimming langorously at the surface of the sea, particularly in sheltered locations, with its maw wide open, filtering its food. It appears to be basking in the sun, hence its name in both linguistic traditions. The species has an enormous mouth and highly developed gill rakers for catching its food and, for this particular sailor, the appearance of its dark form and giveaway dorsal fin (with a tail fin some considerable distance behind), as it feeds in a Hebridean location, is something that makes the heart instantly beat faster!

A basking shark feeding. This is from Wikimedia Commons

My own most memorable encounter with basking sharks was on a yacht trip on the west coast when we called into a group of small uninhabited islands, one of which bears a lighthouse, in the Cuan Barrach ‘the great sea of Barra’, referred to in English as the Sea of the Hebrides. In a channel between two of the islands, there was a group of half a dozen basking sharks slowly swimming and feeding, reaching the end of the channel and turning to make another circuit. Two of the crew went out in a rubber dinghy to quietly drift in the channel in close proximity to the docile monsters, who studiously ignored them.

Of course, such slow-moving and giant beasts are easy prey for the greatest predator of all – humans – and in the years following the Second World War a basking shark fishery was established on the west coast, with well-kent figures like Gavin Maxwell and Tex Geddes, and their colleagues, harpooning and processing the fish, with particular emphasis on their enormous and valuable livers. The ruins of Maxwell’s factory on the Isle of Soay, in a spectacular setting close to the Cuillin of Skye, can still be seen today. While stimulating a series of adventures in the best traditions of derring-do, the industry is blamed even today by some west-coasters for a dramatic fall in the number of basking sharks seen around our coasts. Today, the species is heavily protected throughout UK and EU waters. They are gentle animals – please treat them gently.

The ruins of the basking shark processing facility on the Isle of Soay. Photo © Roddy Maclean

This blogger’s first close Scottish encounter with an iasg-grèine or sunfish came last summer off the coast of Fladaigh, the isle of Fladday, adjacent to the north-west coast of Raasay. It was the dorsal fin that we first noticed, and the inclination was to call ‘cearban!’, but the floppiness of the fin and its lateral bending, combined with the general motion of its carrier, which was languid, to say the least, made us realise that here was something different – and most unusual. As we got close, we realised that we had happened upon one of the most amazing fish in the world’s oceans.

Looking like a head joined to a wavy tail, without an intervening body, shaped, in a faintly comical manner, like a great round disc, the sunfish appears to have been designed by a group of primary school children who delighted in form, regardless of how unlikely that might be to a biologist, and were little concerned with the engineering details of how to propel a considerable bulk through water in a forward direction. The species is surely one of the great biological conundrums – and, one has to admit, given its longevity and wide distribution – successes of the processes of organic evolution.

Sometimes called the Ocean Sunfish to distinguish it from the related Southern Sunfish (Mola alexandrini), the species that moves north with the North Atlantic Drift to visit our waters in summer is to be found in tropical and temperate waters around the world. While they may drift with ocean currents, sunfish can actively swim – generally at a little over a knot, but on occasions putting on a burst of speed to escape a predator (orcas, or killer whales, are known to be among the species that predate adult sunfish). Like the basking shark, the sunfish is of a docile disposition and will not attack divers, but it has been known to leap onto boats. And, as with the basking shark, European Union law protects the species, although this is not the case elsewhere, with its flesh being considered a delicacy in the Far East, particularly Japan and Taiwan.

An Ocean Sunfish in an aquarium. Photo © Per-Ola Norman (released into public domain)

The name ‘sunfish’ comes from the animal’s behaviour when it lies on its side – basking – just under the surface of the water, absorbing warmth from the sun. Unlike the basking shark, swimming at the surface is not a feeding behaviour. Instead, it allows the fish to warm itself, increasing metabolic activity, following a dive to feed in deeper, colder water. The Welsh name, pysgodyn haul, corresponds to the Gaelic and English names, but not all cultures interpret the species in the same way. To some it is a ‘moonfish’ (because of its shape), to others a ‘head alone’ and, in the Scandinavian countries, a ‘lump fish’. The scientific name mola is derived from the Latin for ‘millstone’, the shape of which a sunfish broadly resembles.

It is a generalist feeder, with its prey consisting largely of small fish, squid, crustaceans and jellyfish. Researchers have found that it even consumes eelgrass, demonstrating that it will frequent the seafloor on occasions. The specimen that I encountered off Fladday was light grey in colour, although they can also be brown or white. It was slightly under the average adult size (which is 1.8m long and 2.5m vertically from the tip of its dorsal fin to the tip of its anal fin). But the species can achieve considerable size, reaching 3.3 m in length, with a mass of well over two thousand kilograms! It is also a prolific breeder, with the female known to carry as many as three hundred million eggs, more than any other vertebrate.

If you happen to be off the Scottish coast in a boat, before autumn sets in, keep your eye open for a fin breaking the surface of the sea. It might be one of our two ‘basking sun-fish’ species – fish that remind us of the magnificence, wonder and diversity of the natural world and of the remarkable process of evolution that brought them into being.

This blog was written by Inverness-based writer, broadcaster and storyteller Roddy (Ruairidh) Maclean, whose work highlights the connections between the Gaelic language and Scotland’s environment.

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