The Firth of Clyde

The Clyde's physical shape is not a coastline that happens to be deep. It is a set of ice-cut troughs that the sea has flooded, and the difference explains everything from where the fish are to why the wind behaves as it does.

ICE CUT DOWNWARDS, NOT OUTWARDS. A glacier occupying a valley erodes vertically far more effectively than water does, and it does so below the level the sea would ever have reached. When the ice went and the sea came in, the result was troughs that are far deeper than the shelf outside them. That is why a hundred metres of water sits a few hundred metres from a beach you can walk onto.

SEVERAL OF THE LOCHS HAVE SILLS. A glacier leaves a moraine, or fails to cut through a hard bar, at the point where it thinned. That leaves a shallow threshold across the mouth of a deep basin. The water inside a sill exchanges slowly with the water outside it, can stratify into layers that do not mix, and can develop quite different temperature and oxygen conditions at depth. In practical terms it means two lochs of the same depth on the same coast are not the same water.

THE SHELTER IS TOPOGRAPHIC AND SO IS THE WIND. Kintyre, Arran and Bute break the Atlantic swell, which is why the Clyde has been small-boat water since small boats existed. But the same steep-sided topography channels wind down the lochs, accelerates it, and makes the local wind direction a function of the hills rather than of the isobars. A forecast for the firth is not a forecast for a loch inside it.

WHAT THE DEPTH DOES BIOLOGICALLY. Cold, deep, slow-exchanging basins with soft mud floors are exactly the habitat of nephrops, which burrow in it, and of the large elasmobranchs that hunt over it. They are not, in themselves, productive habitat for the shoaling round fish the Clyde was once famous for, which used the shallower ground and the whole system together.

AND THE NARROWS ARE THE FISHING. Every constriction — between islands, at a loch mouth, over a sill — accelerates the tidal stream, concentrates food, and produces the reliable arrangement of moving water and slack water beside it that predators exploit. On a firth where much of the ground is featureless deep mud, the narrows are disproportionately important.

The Clyde is the place to learn what a fishery collapse looks like from the inside, because it is unusually well recorded and because anglers watched it happen.

WHAT IT WAS. Through the middle of the twentieth century the Clyde carried a sea angling fishery of a scale that is difficult to credit now: cod, haddock and whiting in quantity, a long-running international sea angling festival built on them, and a common skate fishery whose fish were the largest routinely caught anywhere in Europe. Charter fleets worked out of the firth's towns on the strength of it.

WHAT HAPPENED IS NOT ONE THING. Sustained heavy fishing pressure on the round-fish stocks; a change in the pattern of trawling that followed the removal of long-standing spatial restrictions on the firth; the removal of large predators from the system; and the accumulated effect of a nearly enclosed basin absorbing all of it with little exchange. Different accounts weight those causes differently, and the argument is live rather than settled.

WHAT IS NOT IN DISPUTE is the outcome. The demersal round-fish fishery is commercially finished. Cod, haddock and whiting are at a small fraction of their former abundance. The commercial fishery is now overwhelmingly nephrops and scallops. The angling festival that was built on the old fishery does not run on it.

THE SKATE ARE THE OTHER STORY, and it runs the other way. Common skate — now recognised as two species, and critically endangered — persisted in the deep basins, and the Clyde holds one of the most significant remaining populations in the world. That fishery is now catch-and-release, closely studied, tagged, and supported by anglers who have become a substantial part of the science. A marine protected area was established around it.

WHY THIS BELONGS ON A FISHING SITE rather than in a policy paper. Because a reader arriving at the Clyde with a forty-year-old book, or a reputation absorbed second-hand, will fish for something that is not there and conclude they are doing it wrong. And because the Clyde is the clearest available demonstration that a sea fishery is a thing that can be lost, in a lifetime, in a place people are still fishing.

A description of the present fishery, written to be useful rather than to protect a reputation.

THE SKATE FISHERY IS THE HEADLINE and it is a specialist one. It is deep-water boat fishing over the soft basins, it is catch-and-release without exception, and the handling matters enormously: these are large, slow-growing, critically endangered animals and a badly handled fish is a real loss to the population rather than a bad day. Anglers fishing it are generally working with the tagging and recording programmes, and that is the way into it.

SPURDOG ARE PRESENT IN NUMBERS and have recovered strongly in these waters, to the point where they are frequently the fish that finds the bait first. They are a shoaling deep-water dogfish with a spine in front of each dorsal fin, and they need handling accordingly.

THORNBACK AND OTHER RAYS over the cleaner mixed ground, through the warmer months in particular.

MACKEREL AND POLLACK in season — mackerel inshore in summer, pollack over the kelp edges and around the rocky island shores through much of the year. Coalfish over the same ground and generally deeper.

WRASSE on the rocky shores in summer, which is a straightforward and genuinely good shore fishery here.

SEA TROUT along the shores and around the burn mouths, which is an old Clyde tradition and a demanding one, weighted to spring and early summer.

AND CODLING, WHITING AND HADDOCK exist rather than abound. A reader should expect to encounter them and should not plan a trip around them.

WHAT DRIVES THE SEASON is less the water temperature than in the North Sea and more the wind, because the fishing here is largely boat fishing in a firth where the wind decides whether you go out. The practical calendar is: settled spells from late spring through early autumn for the deep-water fishing, summer for the shore and the wrasse, and a shore fishery through the colder months that is quieter but perfectly workable in shelter the open coast does not have.

The Clyde's particular safety problem is that it does not look like the sea, and the consequences of getting it wrong are the sea's consequences.

THE WATER IS COLD ALL YEAR IN THE DEEP. Surface temperatures in the sea lochs rise in summer but the basins beneath do not, and a person in the water in a firth in July is in cold water. Cold water shock — the involuntary gasp and the loss of breathing control in the first seconds — decides the outcome of an immersion far more than swimming ability does.

THE DEPTH IS IMMEDIATELY OFFSHORE. A kayak or small boat a couple of hundred metres from a loch shore may be over sixty or eighty metres. There is no shallow margin to stand up in, and a swim back is a swim in cold water rather than a wade.

THE WIND IS A LOCAL PHENOMENON. Steep-sided lochs channel and accelerate wind, and they do it in a direction set by the hills rather than by the general forecast. A loch that was glass at launch can be unworkable an hour later while the shipping forecast for the firth has not changed. Wind against tide in a narrows produces a short steep sea out of proportion to the wind strength.

THE STREAMS IN THE NARROWS ARE STRONG. A paddled craft can be held stationary or set backwards through a constriction, and a drifting boat can find itself carried further and faster than intended.

AND THE FIRTH IS BUSY. Ferries run fixed routes on schedule, commercial traffic uses the deep channels, and there is naval activity in parts of it. A small craft is difficult to see and has no right to be where a ferry is turning.

WHAT ADDRESSES IT is unglamorous and consistent: a buoyancy aid worn rather than stowed, a means of calling for help carried on the person, a genuine wind plan with a stated turnaround time and an escape shore, and telling somebody ashore where the craft is going and when it will be back.

The Clyde's great virtue is that it is sheltered. Kintyre and the islands keep Atlantic swell out, the lochs are enclosed, and on a great many days the water is flat when the open coast is not. That shelter is real, and it is also the mechanism, because it makes a place look benign where the consequences of going in are as serious as anywhere in Britain.

WHAT IS ACTUALLY UNDER THE BOAT. This is a drowned glacial trough. The main basins and several of the sea lochs exceed a hundred metres within a short distance of the shore, which means a kayak a few hundred metres off a loch side may be over eighty metres of water. That deep water is cold all year — the surface warms only thinly — so immersion in July is immersion in cold water, the gasp response and loss of breathing control arrive within seconds, and there is nothing to stand on and frequently nobody in sight to see it.

THE FLAT SURFACE IS DOING NOTHING TO CHANGE ANY OF THAT. It is only removing the signal that would otherwise make somebody wear the buoyancy aid rather than sit on it.

THE WIND IS MADE BY THE GROUND, NOT DELIVERED BY THE FORECAST. Sea lochs are steep-sided trenches. Air drains off high ground, accelerates downhill and arrives on the water from a direction the synoptic chart does not predict, at a strength it does not predict either, with no change in the general weather to announce it. A loch that was flat at launch can be unworkable within the hour while the firth's forecast stays accurate and unchanged. Treat the loch's own wind as the forecast, fix a turnaround time and a named escape shore before launching, and read any increase as the beginning of a trend rather than as a gust.

THE NARROWS ARE THE THIRD ELEMENT. Streams between the islands and at loch mouths run strongly enough to hold a paddled craft stationary, and wind against one of them produces a short steep sea in a place that is otherwise sheltered. That is the combination — katabatic wind off the hill, meeting a stream through a narrows, on a small craft, over cold deep water — and it is a sequence rather than a list.

AND THIS IS A WORKING WATERWAY. Scheduled ferries on fixed routes, commercial traffic in the deep channels, and naval movements in some areas. A kayak or small boat is very hard to see from a ship's bridge and cannot get out of the way of a vessel that is already committed to its course. Know where the ferry routes are and stay off them, cross channels at right angles and quickly, carry something that makes you visible, and never assume you have been seen.

WHAT ACTUALLY HELPS. A buoyancy aid worn rather than carried. A means of calling for help on the person. A plan for the wind rather than a hope about it. Not going alone, particularly out of season when there is nobody else afloat to notice. And checking the current inshore waters forecast and the tidal streams before launching — the shelter is genuine and it is not a substitute for either.