Was this the whale inside which Jonah perhaps found himself?
Ireland’s coastal waters remain one of the North Atlantic’s great habitats for sharks. Two species in particular capture the imagination: the porbeagle, a fast, warm-blooded-looking predator of cool temperate seas; and the basking shark, the huge, gentle plankton-eater once harvested in vast numbers off the Irish coast. Their stories are very different, but both illuminate the changing relationship between people and the sea: from commercial exploitation to scientific study, wildlife tourism and legal protection.
The porbeagle shark (Lamna nasus) is a powerful member of the mackerel-shark family, closely related to the mako and great white. It occurs in the cool waters of the North Atlantic and Southern Hemisphere and has long been prized for its firm flesh as well as its fins. The largest porbeagle reported from Irish waters weighed 365 lb and was landed off Achill Head in 1932. Concern over the species has grown sharply since the early twenty-first century. In 2013, CITES placed the porbeagle on Appendix II, meaning that international trade in porbeagle products must be controlled and accompanied by evidence of legal and sustainable origin. In European Union waters, target fishing and bycatch retention are prohibited: vessels may not fish for, retain, tranship or land porbeagles.
The much larger basking shark (Cetorhinus maximus) is altogether more peaceable. Easily recognised by its towering, sometimes floppy dorsal fin and vast open mouth, it is the world’s second-largest fish after the whale shark. In Kerry, it was known as ainmhide na seolta—“the monster with the sails”—while the old Gaelic saying chomh sámh le liamhán gréine means “as tranquil as a basking shark”. It is also commonly called the sunfish, for its habit of feeding near the surface. Was this the whale inside which Jonah perhaps found himself?
Basking sharks arrive in Irish waters in spring to exploit blooms of zooplankton, filtering seawater through comb-like gill rakers as they swim. For much of the twentieth century, their disappearance in autumn encouraged the belief that they simply vanished into the Atlantic. Satellite-tagging studies have since shown a more complicated picture: some sharks range towards the waters of Portugal, the Canaries and Cape Verde, while others may remain in or near Irish waters through winter.
For centuries, however, people saw basking sharks principally as a floating industrial resource. Their immense livers yielded oil that could be used in lamps, medicines and the treatment of wood. Before paraffin became widely available, shark-liver oil was a valuable illuminant, and there are records of it being used for street lighting in Galway, Waterford and Limerick in the eighteenth century. The commercial value of basking sharks was not confined to their oil. Their skins could be processed into shagreen or leather, while their flesh was sometimes used as food or bait. The wider whaling economy also increased demand for whale-derived commodities, particularly baleen—then routinely called “whalebone”, although it was not skeletal bone at all. Baleen consists of flexible, keratin-based plates that hang from the upper jaws of baleen whales and filter food from seawater. Dried and cut into strips, it was strong, light and springy: ideal for corset stays, stiff collars, umbrella ribs, whip handles and numerous other items. Its commercial value drove whaling fleets across the Atlantic and beyond, creating an industrial background in which every large marine animal might be assessed for oil, skin, meat or some saleable by-product.
In Ireland, the hunt for basking-shark oil drew currach fishermen from the western seaboard out after these immense but harmless animals. The work became easier after 1760, when Thomas Nesbitt of Inver, County Donegal, developed a swivel-gun harpoon. Nesbitt had established a whale-and-shark rendering works in Donegal Bay the previous year. By the early nineteenth century, shark-oil works were operating along the north and west coasts and on several islands.
One of the oldest recorded Irish fisheries lay at Sunfish Bank, roughly 30 miles off Achill Island. On productive days, currach crews might take thirty or forty sharks. The huge liver was removed, cut into pieces and heated to extract the oil; a single shark could produce seven to ten barrels. The market declined during the later nineteenth century, and the Sunfish Bank fishery collapsed in the 1880s. The story resumed, with devastating consequences, at Keem Bay on Achill’s Atlantic coast. A targeted fishery began there in 1947, an era before marine conservation had entered public policy. The sharks were netted and killed for their liver oil. The scale was extraordinary: 1,808 were killed in 1952 alone. Between 1950 and 1964, some 9,000 were taken; by the closure of the fishery in 1975, approximately 12,342 basking sharks had been killed at Keem. The sharp decline in catches is now regarded as powerful evidence of local overexploitation.
Ireland’s legal position has changed fundamentally since the basking shark was declared a protected wild animal under the Wildlife Act 1976. Following regulations that took legal effect on 3 October 2022, it is an offence, without licence or permission, to hunt or injure a basking shark or wilfully interfere with or destroy its breeding or resting places. The species also remains listed on CITES Appendix II, where international trade is regulated. But protection on paper is only part of the story. Basking sharks are vulnerable to accidental capture, vessel disturbance, entanglement, pollution and changes to the plankton-rich marine conditions on which they depend. Their slow growth, late maturity and relatively low reproductive rate make recovery from heavy exploitation a long process.
There have been encouraging signs. In 2010, hundreds of basking sharks were reported along the Inishowen Peninsula between Lough Swilly and Lough Foyle. The ending of drift-net fisheries and the growth of public awareness may have helped reduce some pressures, although apparent increases in sightings may also reflect better reporting rather than a straightforward population recovery.
The work of the Irish Basking Shark Project and the Irish Whale and Dolphin Group has transformed what is known about these animals. Dr Simon Berrow and colleagues have used coloured identification tags and satellite transmitters to study individual sharks and their movements. Earlier tagging work demonstrated both the potential for site fidelity and the likelihood of much longer migrations than had once been imagined.
A shark’s fin slicing through a calm Irish bay is now more likely to prompt binoculars, cameras and a call to a marine-wildlife group than the launching of a currach with harpoons.
