With Britain’s seas in crisis, is it a case of so long and thanks for all the fish?

“Why so many sunk fishing boats?” I asked.

“There’s so few fish around and so few days they can fish. They don’t make much money so they go out in weather they shouldn’t and skimp on maintaining their boats and...” His shrug said it all.

The seas are in crisis. Pollution, climate change, dead zones, rubbish, invasive species, noise, acidification and overfishing are the roll-call of man-made insults that are changing our oceans for the worse.

But a glance at a beach on an early summer’s day or a two minute news report on albatross chicks dying, their intestines blocked with plastic picked from the ocean in lieu of food does little to alert us to the true scale of the problems beneath the waves. Nor does it galvanize politicians to the drastic action necessary to restore the seas and their inhabitants to health.

And we need the seas to be healthy. Rainforests are called the lungs of the world. Yet the unromantic phytoplankton in the upper layers of the sea produce 50 per cent of all the oxygen in the atmosphere. And a large proportion of the world’s population depends on the oceans’ declining fish stocks.

A diagnosis of the sickness in our seas and the treatment needed can be found between the covers of Ocean of Life: How our Seas are Changing, the new book by York University’s Professor of marine conservation Callum Roberts.

A few years ago he predicted a bleak future for the seas, “mud and worms,” was his description of what we would be left with if we carried on our present course of consuming and polluting. Ocean of Life suggests that we have not yet even thought about changing course.

Roberts recalls visits to Whitby, still referred to today as a fishing port, in the 70s when the harbour was packed with trawlers and the cod they caught weighed in at 50lbs. On the day I spoke to him, it was announced that one of the four remaining trawlers in the port had been sold, its owners despairing of making a living. Why?

The trawlermen blame the EU, the Government and foreign fishermen. For North Sea fisheries, the blame lies in overfishing – trawling large fish out of the sea, not giving the stocks a chance to recover and repeatedly fishing the same ground, destroying the very seabed ecology that should support fish populations.

A sunny July day in Whitby and the battered fish and chips are flying out of the harbourside chippies. But gone are the days when the resort’s traditional dish was a guarantee of Whitby fish. The fish which ends up in batter on Pier Road will most likely have come from the North East Atlantic, caught in the waters between Scotland and Iceland and frozen at sea.

Many of those in the fishing community insist the quotas are not only strangling their already fragile livelihoods, but they are now unnecessary and that they’ve “never seen so many cod”.

It’s argument Prof Roberts refutes. While some fish stocks in the North Sea are staging a comeback, they are starting from a very low level and many of the populations are not in a healthy breeding state.

“The Grand Banks off Newfoundland are a scientific example of what happens when cod stocks are fished out,” he says. “The Banks, which had once supported so many cod you could throw a bucket over the side of your boat and catch them, were eventually closed to fishing.

“However, despite 20 years respite from trawling, the cod have not returned in any significant number – having been fished out, the number of eggs and young cod are no longer high enough to survive predation. They are eaten by crabs, predatory fish and jellyfish before they get to adulthood.

“The situation we face in the North Sea may not be in this intensive care state, but it is critical.”

Prof Roberts warns against the problem known to scientists as “shifting baselines”. When the fishermen say they can’t remember so many cod off Whitby, they are not working from data, but from recent memory.

Catches may be more abundant now than they were 10 years ago, but in truth they are nothing compared to the volume of fish and the whoppers being landed from the North Sea 40 years ago.

Cod should reach sexual maturity between 7 and 8lbs. However, North Sea cod are now ready to spawn at 4lbs, a red flag to biologists that this is a species still under severe pressure.

Unless strenuous conservation measures are applied, especially in fishing methods which destroy the seabed such as bottom trawling and scallop dredging, the North Sea and the communities which make something of their living from it will suffer.

There is an example of what may face our local waters not far away. “Go and look at the Firth of Clyde,” says Prof Roberts.

“It used to be a rich fishing ground and now there are hardly any fish left.

“Now they just fish for scallops and prawns, both highly destructive methods of fishing.”

He described a dive in the Irish Sea after scallop dredgers had been through, raking their gear through the muddy bottom scooping up scallops but also fish, crabs, rocks and invertebrates – the whole ecologically crucial top layer of the seabed.

“In the whole dive we saw just four living things and one of those was dredge damaged and dying.”

The solution? In chapter 19 of Ocean of Life, Prof Roberts, who has previously been a member of the Marine Reserves Working Group, proposes a New Deal for the oceans.

By the time you have been steadily depressed by chapter after chapter describing the threats to the oceans, you realise that we as a population are treating the seas like the man who jumps off the top of a skyscraper. He passes the 25th floor on the way down thinking, “So far so good”.

The New Deal for the Oceans demands urgent action that will meet with resistance from vested interests and politicians all historically too willing to take the easy way out.

Prof Roberts suggests that around a third of the seas will have to be closed to fishing to allow fish stocks and their crucial supporting ecosystems to recover.

Ocean of Life is popular science writing at its best. Professor Roberts is one of those scientists with the ability to take the hard science that is published away from our gaze in academic journals, mix it with experience and anecdote, then write it down in an accessible and entertaining manner.

This book should be on every A-level biology student’s desk, on every MP’s summer reading list and especially on the desks of the men and women who set fisheries and conservation policy for the EU, the UN, the USA and the fast developing, resource hungry countries in Asia.

Setting aside anecdotal evidence, the hard science shows the rapid and profound damage we are doing to the oceans and outlines the prescription for the recovery of our most important ecosystem and life-support system.

And to finish the tale that opened this piece?

The diver was into the whiskey that night (it was Irish) because he’d found a body trapped in the hull, pinned behind a mass of gear and cable that had shifted when the boat sank.

“I thought, no way I’ll get him out without cutting gear. I turned and finned away, and as I got to the end of the passageway I sensed something behind me. I turned.

“There he was. Hanging in the water over my shoulder.

“How the body got from behind that pile of gear I’ll never know. It was like he wanted to be out of that boat and be buried on land.”

Ocean of Life: How the Seas are Changing by Professor Callum Roberts is published by Allen Lane, priced £25. To order a copy through the Yorkshire Post Bookshop call 01748 821122.