Britain's lost marine megafauna
Once upon a time, Britain's seas were boiling with monsters. Professor Callum Roberts, a marine conservation expert, takes a look at our lost marine megafauna.
“The crews caught the fish as fast as they could bait and haul and it is stated that when any of the cod broke from the hook, great monstrous sharks as blue as if painted with a brush darted round the ship’s side and swallowed them in an instant.”
This passage could easily be mistaken for an account of fishing in tropical seas swarming with sharks. But the cod referred to are not exotic species like groupers, but the cod of the North Atlantic. The report was written in 1862 and describes the experience of fishermen when they first discovered the rich – and at that time unexploited – Rockall Bank, 200 miles northwest of Scotland. By then, the North Atlantic had been intensively fished for hundreds of years, so the abundance, size and voracity of life at Rockall came as a shock.
As well as sustaining extraordinary numbers of large blue sharks and metre-and-a-half cod, Rockall in the mid-19th century supported “numberless whales sporting and rising on every side”, large groups of dolphins, and seabirds tame from unfamiliarity with people. Today, we tend not to think of Britain as a place that could ever boast a profusion of giant fish and cetaceans, but even as little as a century ago it was a very different place. The seas around our islands were home to remarkable marine megafauna.
Armies of porpoises
British waters are among the most productive in the world, or at least they were before we reached our present state of extreme overfishing. Britain lies moored amid one of the largest continental shelves in the world. Such shallow seas, stirred by tidal currents and winter storms, are rich in nutrients essential for plankton growth. Copious plankton can support huge populations of shoaling ‘forage’ fish, such as herring, pilchard and sprat. Up to the early 20th century, shoals of herring so vast they appeared limitless approached British coasts every spring and summer to spawn. One 18th century traveller to Loch Fyne on Scotland’s west coast commented that it contained one part water and two parts herring. Dense pilchard shoals containing hundreds of millions of fish crowded cliffs and bays of southwest England, passing like dark summer clouds across the blue waters.
Many species of whale – including the world’s largest, the blue whale – lived in or visited our shores, drawn by the immense quantities of plankton and fish. Whales were among the first species targeted by people, with significant whale hunts off southern England by French and Basque whalers from at least the 11th century. Medieval records of a decline in whale strandings suggest a fall in abundance by the 14th century, probably as a result of hunting. However, faster swimming species with less blubber, such as fin and minke whales, remained plentiful until the late 19th century when steam-powered whaleboats were introduced. After that, 20th century persecution so reduced whale numbers that in most places a sighting is a rare joy today.
Smaller cetaceans such as porpoises and dolphins were once far more common than they are today. An early 18th century parliamentary report stated, “Porpoises abound in almost innumerable shoals on the western shores of Ireland.” In 1750, Charles Smith wrote in his history of Cork: “I have seen an army of porpoises, as it were, guarding the mouth of Youghall harbour, where they made great havoc among shoals of salmon which were then entering the Blackwater River, and even chased some on shore.” Similar eyewitness accounts can be found from places all around the United Kingdom up to the early 20th century when numbers began to plummet. Today, the entire UK population of bottlenose dolphins numbers only five or six hundred.
Ancient predators
Also in pursuit of forage fish were sharks, such as the blues seen at Rockall, joined by porbeagle, mako, thresher, tope and others. Blue sharks were sworn enemies of the pilchard fishers because they passed “up and down the nets, and often when tearing the fish out of the net cut out great pieces of it ”. Schools of immense bluefin tuna troubled fishers in much the same way, often crowding boats as the nets were hauled to feast on fish held in the meshes.
We have lost much of our magnificent marine megafauna by past indiscriminate slaughter for food, oil, and fur, and by overfishing their prey. Today, we continue to destroy small cetaceans by permitting the use of pair trawls and gill nets that kill thousands around our coasts every year. In recent decades, sharks too have become targets, metamorphosing from nuisance to valued commodity. Pursued for their fins, the seas are today being stripped of these ancient predators.
To bring back our megafauna and the many other species that have suffered directly or indirectly from fishing and hunting, we urgently need more protection. To be effective, that protection must include bans on destructive fishing methods like pair trawling and gill netting, or at least strict limits on where these gears can be used. And fishing restrictions have to be underpinned by extensive networks of marine reserves that the best available science suggests should cover around 30% of our seas. In a world with ever-rising human needs, we cannot return the oceans to some primordial state. But we should set our sights for conservation much higher and aim to restore some of the splendour of life in the sea that has been lost through centuries of overexploitation.
Callum Roberts is Professor of Marine Conservation at the University of York and author of The Unnatural History of the Sea.
