The Salmon: The Extraordinary Story of the King of Fish

Important elements like phosphorus and nitrogen determine marine productivity. These either wash onto the shelves that are the underwater extensions of landmasses, or are pushed from below in the deep ocean by upwellings as ocean currents mix, driven by the Earth’s rotation. Areas of the ocean vary enormously in their productivity, the North Sea and the Grand Banks being shallow expanses and exceptionally fertile, as contrasted to vast parts of the mid-Pacific where the water, as you peer into it with the sun behind, is startlingly clear precisely because there is so little plankton and suspended material. It is as void as sterilised bottled drinking water. In other places millions of plant cells can occupy one cubic foot of seawater.

This partially explains what has been called the ‘explosive growth’ which salmon display after leaving their freshwater nurseries as six-inch smolts.

Marine biology and marine research have made quantum leaps in recent time. Two areas of rapidly advancing research concern life in the bathymetric deeps, where life-forms have been discovered way below depths at which it was formerly thought any life at all could exist, and secondly in the pelagic or surface skin of the ocean. Although we now know that salmon obtain food from depths of as much as 800 metres in the dimmed realms of the sperm whale, and can stay at 400–600 metres for as long as 24 hours, it is in the surface ocean layer that smolts have to survive when they leave rivers.

Their departure is called the smolt ‘run’. The small fish leave their natal river for the great unknown when prompted by rising temperature. A government fisheries department in Scotland used infra-red images at night on a tributary of the River North Esk to watch smolts assembling for the ‘run’. The technology was not perfect; rising water levels lost the images of fish, but the presence of smolt-traps further downriver showed that smolts did indeed continue running in high waters. For the bigger picture the technology served adequately. It showed that fish shoaled in small parties of three to six, they used the core of the current for propulsion, and they descended rivers pointing seaward.

Tagging with microchips has established another new finding. Smolts enter the sea in a mass to minimise predation. Having travelled downriver in small schools, they pack to go to sea, then closer to the sea becomes an assembly point. The reason is the same as why other small fish shoal – it enhances an individual’s survival chance to be one of many congregated in a dense mass.

A salmon river is occasionally blessed with egg-bearing gravels all the way up its sinuous length. The Miramichi in Canada is an example of a spawning bed over a hundred miles long. Hen fish will sweep out redds and lay their eggs in them from the narrowest streams at the top to the wide, gravelly wash-out bars near the river-mouth. To coordinate the smolt runs, however, the development of eggs into fry and parr and then into smolts in the headwaters of the river must be earlier in the season, so that when these young shoals of salmon go seawards they do not miss the camouflage of other shoals of smolts which have matured later and which are waiting nearer the river-mouth.

Accordingly, in northern Scottish rivers parr begin to go silvery, and turn into smolts or ‘smoltify’, as early as March in the headwaters and as late as May lower down. To prepare them for ocean life, away from the shady corners and dark shadows of natal streams, they develop an ocean livery. Their skin grows a layer of silver guanine crystals. These crystals arranged in verticals rows act as mirrors, camouflaging the little fish by reflecting its surroundings.

The keen perception of Dr Richard Shelton, formerly head of the government’s marine laboratory in Pitlochry in Scotland, noted that the only parts of the smolt to remain unaltered are the black edges to the fin and tail. He believes these are helpful visual aids to other smolts in keeping the pack together, whilst not giving too much definition away to predators.

To help the smolt register where it originated, and to find its own personal natal stream later as a fully grown fish, the hormone thyroxine is raised temporarily to allow the small brain to take in vital extra survival information.

The cohort of smolts journeys down the river, making the little flips and splashes familiar to springtime anglers, and reaches the sea to coincide with feeding opportunities. The oldest smolts reach the salt first and the youngest, maybe only a year old, go last, an order which is reversed when they return as adults. A critical feeding assignation is with the outburst of sand-eel larvae on the sandbanks.

The similar appearance of different smolts is deceptive. Those from the southern edge of range, France and Spain, are a fraction of the age of individuals from colder northern rivers. Whereas many southern European smolts are just over a year old, those from Arctic Norway, Greenland and Ungava Bay may be seven before they risk life at sea. From Iceland and Scotland smolts have dwelt from between two and five years in the river. The age difference reflects the length of the growing season, further north, less time.

It is an extraordinary thought that physically similar fish, at the same development stage, vary in age by so much. There are no obvious parallels in bird or mammal biology. Possibly there are comparable patterns in other fish, but none comes to mind. Salmon evolution is supreme adaptation.

What happens after the entry into seawater has recently been tracked in an internationally funded programme codenamed SALSEA-Merge. SALSEA is the most remarkable research on a fish at sea in recent time. The European Union, Canada, the USA, the Total Foundation in France, the Atlantic Salmon Trust in the UK and a variety of universities and agencies combined to fit out the RV Celtic Voyager and two other vessels with proper equipment, and then put the right people on board who knew what questions to ask and how to get answers.

The results fill in another corner of the lifestyle jigsaw.

The research boats spent three years catching around 27,000 juvenile salmon from 466 different locations in the North Sea, the Norwegian and Irish seas, and generally in the north-east Atlantic around the Faroe Islands and Iceland. Information from 284 out of Europe’s 1,700 salmon rivers from nine countries was used in genetic sampling and analysis. The biggest sample came from Scotland, followed by Norway. By targeting the most productive and the largest rivers, the SALSEA team reckons that 80 per cent of Europe’s productive salmon area was embraced by the research effort. The resulting picture then is a clear story about European salmon, including Russia and Scandinavia, up to 2011.

The novel side of the analysis was the use of genetics. Only recent science allows researchers to find out where a fish comes from. Work on Ireland’s River Moy had already shown what a sprinkling of other rivers had found too – that inside their catchments salmon stocks can be divided up into genetically discrete populations. It was true of a minority of rivers, but demonstrated the impressive complexity of salmon adaptation.

The Atlantic salmon in some form or other has been occupying European and North American rivers for 60 million years. In that immense time it has developed local strains to adapt to local conditions. Then the last Ice Age ended, with a thaw that peeled back the ice-covered land over all Britain north of London. A mere 15,000 years separates us from the frigid conditions that dominated before. In cosmic terms it is a blink in time. Salmon saw pristine territory opening up in front of them, and occupied it.

Rivers in Scotland have plenty in common with other rivers in salmon range. They are spring-fed. These springs can come from hundreds of feet below ground and each one has a differing chemical composition. Also, the springs bubble from the ground loaded with different temperature readings, dependent on their depth.

Variations between springs account for differing populations of salmon. For the scent in each stream, and the mineral contents, differs from that of its neighbour. Salmon have brilliant olfactory senses, being able to pick out the most dilute odours from home-stream chemistry even through a fog of additives and man-made complexities. The fish’s ancestors have used that water and over time adapted to it.

Sometimes that adaptation will translate into an identifiable genetic type. SALSEA went to sea armed in advance with the genetic map of many rivers. The researchers were hunting smolts, young salmon entering an alien saltwater world pregnant with feeding and with threat. What galvanised researchers to go to all this effort? The answer to that question is both simple and complex. At the simple level, it is because the salmon is important enough to justify it – it is a glittering symbol of environmental wellbeing. The complex answer backtracks in time.

In the 1960s European rivers had seen prodigious runs of salmon. The silver bonanza from the spring tides re-ran the programme of fresh shoals arriving through the year and it seemed as certain as the sun dropping in the west that from the start of spring these great leaping, wild, sparkling fish would go on and on revitalising rivers which had gone doggo for the winter.

Then a decline commenced. Fewer and fewer salmon came back in the 1980s, and then the 1990s. The canaries in the mine, or anglers, found their enticing presentations drifting across the stream undisturbed. Nothing jumped. Nothing swirled at the fly. The waters rolled to sea unruffled. The rivers missed their most dramatic occupant.

A few rivers had installed fish counters, usually consisting of electronic beams broken by an upstream-swimming fish, and these counters, logged by computer, were telling an alarming story which backed up the anglers’ perceptions of fewer silver visitors.

It was estimated that in the 1960s and 1970s the population of salmon in the eastern Atlantic was around eight to ten million fish. In America and Canada, where many rivers had been dammed, where forest clearance in river-country had silted up river-beds and traumatised ecosystems, there is another story of dwindling fish, but we will revisit that side of the tale later.

The decline from abundance was giving rise to serious worry.

In places where smolt survival was being measured, such as at Scotland’s North Esk government monitoring station, and the Bush and Burrishoole system in Ireland, young sea-going smolts had once returned as salmon in numbers approaching 15 per cent of the outgoing migration. This figure was falling and falling steadily. It fell to eight and then as low as five per cent. On the River Conon in the northern Scottish Highlands, where they can measure these things, the return rate of smolts in 2011 was four per cent. In some rivers the number will be even less.

For anadromous fish, which live at sea and breed in freshwater rivers, this figure was low – very low. It told scientists that ocean-wide changes were occurring. Somewhere out there a black hole was consuming the small silver fish that used to fatten in the larder of the north-east Atlantic, before returning to their birthplaces in the pebbly streams. In some American rivers spawning pairs were down to a handful of pairs, a chilling brush with death equal to a doomed scenario.

The most obvious subtractions from salmon runs were then looked at and addressed. Salmon netting, which was recorded as having been prosecuted in some parts of the UK and Europe since the twelfth century, was an obvious target. Here was an industrial-scale subtraction, taking fish before they could breed. Furthermore, it violated one of the tenets of modern fisheries management – that you must know what stock of fish you are taking.

Netsmen took salmon offshore as they migrated past. No one had a clear idea which rivers they were due to swim into. A salmon in the net was a salmon in the net; they all looked much the same. They fetched the same price, too. Logic demanded that random salmon capture cease. On the back of the idea that netting was ‘indiscriminate’, harvesting individuals valuable to species survival alongside those from more numerous components of the migration, appeals were launched to save salmon by buying out or leasing netting stations. Many were laid off and mothballed and bought out. In Scotland alone the catch by nets was ratcheted down from around 100,000 salmon a year in 1990 to 13,000 twenty years later.

Salmon netting still exists in a few places in 2013. Norway remains unreconstructed about salmon netting. Scotland has a handful of active netting-stations, resistant to being bought off and encouraged by rising wild salmon prices, England even fewer. The Norwegian Saami people from the far north, with precious little to sustain them, still net salmon on the Arctic coast. In a conservation milestone for salmon, Iceland terminated netting at sea as far back as 1932. Pressed by the European Union, the west-coast Irish drift nets were outlawed in 2007.

The most important salmon-netting haul in modern times was taken off Greenland. It commenced in 1959 when gill-netters working the fjords were startled to find glittering salmon in the mesh. A boom in salmon commenced, which pulled in drift-net fishers close to Greenland’s western shore from Denmark, the Faroes and Norway. The working season was August to October, with the winter iced over. Catches rocketed, peaking at 2,689 tons in 1971. All of a sudden salmon, which are a rare fish in the sea, were being caught like mother cod, which can lay millions of eggs. The International Council for the Exploration of the Sea (ICES) reckoned the Greenland operation in winter 1972 had removed a third of all the salmon locally present. As more attention was paid to what exactly was being caught the fish were traced to the east coast of America and Canada and, secondly, older female salmon from Scotland.

Something had to be done. The solution was devised by an Icelander called Orri Vigfusson, who is now a household name in salmon conservation. A partner in a herring fishing family that hit hard times when herring runs shifted, Vigfusson was familiar with the vagaries of fishing. Basically in sympathy with remote communities eking out precarious existences, Vigfusson saw that in order to endure the solution had to be fair. An international arm was needed to lend support and the quotas discussed at the negotiating table were assembled by the North Atlantic Salmon Conservation Organisation (NASCO), a multi-member body formed in 1984.

Encouraging alternative fisheries for the Greenlanders, and with striking success raising money all across salmon range, Vigfusson made his breakthrough leasing arrangement in 1993. The Greenlanders were not sold down the river – far from it. Their argument that the salmon fattened off their coast was accepted. The payment could be seen as a grazing fee. They were paid to abstain from their rightful fishery, beyond a small permitted tonnage for ‘subsistence’. No salmon could be exported.

The agreements have had to be regularly renewed and reassessed, a lack of finality seen by their critics as a weakness. There have been teething troubles. Greenlanders with limited opportunities for economic activity have exceeded quotas. Annual payments have been withdrawn, and then reinstated when malpractices have been straightened out. The way may have been tortuous, but it has succeeded.

A similar arrangement was reached with the Faroe Islanders, who had been shown how to catch salmon on baited long lines by Danish fishermen from the island of Bornholm who had perfected this art in the Baltic. By 1991 Vigfusson had clinched an agreement with the Faroese, made easier because the Icelandic government already had fisheries access arrangements to their seas with their closest neighbours. The Faroese were the only foreign fishermen allowed to catch Icelandic fish.

Vigfusson had shown how to raise money for salmon protection and how to broker international agreements on a new basis. Tirelessly he had circuited the salmon world, flying from one event to the next, rattling in buses round the bumpy roads on the Greenland coast, meeting one fishing community after another, making addresses and hosting fund-raisers, coming up with ideas for alternative employment, patiently arguing and negotiating. People had faith in his integrity and un-deflected purpose. He crossed national divides and came from a neutral country carrying no historical baggage. Salmon conservation using his model took a mighty stride.

Today there are still anecdotal tales, usually involving Spanish trawlers playing fast and loose with everyone and everything, but in the main salmon netting has being progressively removed as a major factor in European salmon decline.

Anglers knew they had to join the effort to restore the bountiful fish. Inducted in its virtues by an American salmon community almost completely stripped of their iconic east-coast visitor, and championed by the charismatic Alaskan-born angler and conservationist, Lee Wulff, who coined the memorable phrase ‘Gamefish are too valuable to be caught only once’, ‘catch and release’ was introduced to UK anglers around 2005. Since that time it has taken off. The fish is brought to the landing-net as fast as possible, revived by allowing the lungs to re-fill with oxygen, and let go when the body is properly horizontal in the water and the tail-movement quickens.

Talked of and practised by individual anglers for at least a century, especially when the salmon was late-season and coloured, catch and release took a formal position in salmon management relatively lately. Now it applies to fresh salmon in mint condition, not only coloured flabby ones.

Scotland’s Aberdeenshire Dee broke the mould and made catch and release compulsory all season in an unprecedented announcement that caused a mighty stir at the time. But it was done. Other rivers followed suit with milder variations on the theme. Some salmon were allowed to be killed ‘for the pot’ at times of year when runs were bountiful, and restrictions on numbers of fish allowed to be killed were applied to sensitive parts of the run, typically the early spring.

The result? Were there more shoals of salmon pushing the tide up the banks as they swarmed into those waiting river-mouths? Hell, there were! The decline persisted.

It was against this background of dwindling stocks that SALSEA girded its loins to find out what was happening in the part of the salmon zone that remained an almost total mystery – saltwater.

The background to this mystery was not only a fish that was doing a vanishing act, it was climate change. The north-eastern Atlantic, where many European salmon wintered, was warming. No thermometer was needed to discover this. Surf anglers on the north coast of Scotland’s desolate extremities threw their spinning lines baited for cod and hooked sea bass. Previously sea bass had not been caught further north than The Wash in south-eastern England. Exotic fish were dragged up in trawlers all the way to Iceland. Red mullet and sea bream edged up the latitude line. Coral reefs crumbled in unfamiliarly warm waters. Disc-shaped sunfish, previously only ever seen, and then rarely, off the south coast, were hauled onto boats far up the coast of Britain. From sardines to whales, fish moved northwards. Smolts were not immune; their pathways adapted too.

Oceanographers confirmed it: the North Atlantic was warming. For fisheries this presented challenges.

In 2011 there was a furious row in Europe’s fishing states when Iceland, not hitherto invited to the meetings which allocated quotas amongst traditional fishing nations, and not an EU member, discovered big shoals of mackerel swarming around its north coast, and started catching them. The Faroe Islands found and did the same. Tempers flared. The two small states became overnight pariahs. These fish ‘belonged’ to fishing nations further south. Iceland and the Faroe Islanders argued that the mackerel in their waters were in prime condition with top-notch fat content, perfect for market. For countries further south to limit their new bonanza was bizarre; the fish belonged to whoever had possession of them. The argument sputtered on. National politics had run up against fluctuating natural cycles, a test for diplomacy.

Fish follow temperature bands which are the conveyor belts for food. The mackerel do not care whether they swim off Iceland or off Ireland, they register the volume of shrimp and squid and other high-octane titbits that can be gorged upon, and follow them. Mackerel are not anadromous like salmon, with both a freshwater phase and a saltwater one, but their extreme mobility tested the capacity of nation states to live in a changing world. There were parallels with salmon politics.

The background to the search for smolts from European rivers was the same warming North Atlantic. There was a simple distance factor: the smolts from the southern extremity of salmon range in rivers in northern Spain had a longer journey to reach the winter food supply; further to swim, in hostile territory. All along the journey were the enhanced risks of predation and starvation. Conversely, as freshwater temperatures were also rising, smolts were growing faster in natal streams, and were bigger and often younger when they reached the salt. Ratcheting up the pressure, survival rates of fast-growing smolts are lower.

Celtic Voyager and two other research vessels embarked on their exploratory fishing trips in a world being re-drawn by dynamic flux.

Anxiety about the Atlantic salmon was sufficiently syncopated and international to produce the SALSEA programme. Although salmon smolts were the tools, the programme, lasting over three years from 2008, was designed to advance the understanding of ocean ecology and fish genetics. The authors even talk about hopes that they have provided invaluable data for ‘the future ecosystem-based management of the oceans’. Big aims.

To catch these very small fish in a large piece of sea they adapted a standard small trawl for smolt capture. A small-mesh net was pulled on two side ropes and kept on the surface by large floats on each side. At the ‘cod-end’, or last compartment in a narrowing cone-shaped net, was the fish ‘box’ accumulating smolts. The smolt trawl was towed in arcs at speeds of three to five knots, anything from 150 to 400 metres from the mother ship. It was 155 metres long with a mouth forty by ten metres. The main thing was – it worked.

Quantitative results varied by region. The report cites one case where 233 trawls netted 1,728 smolts and 53 adult salmon, at a rate of 3.4 fish per trawl. This trawl had hit a migration ‘pathway’.

The long-awaited paper, which included data collection from as far back as 1999, was published in January 2012. Authors Jens Christian Holst and Ken Whelan warn that owing to cost no such programme is likely to be done again. So we should heed what they discovered.

The location of smolts was closely linked to ocean currents. Differences in temperature and salt content change the density of seawater, which in turn drives global ocean circulation through the medium of currents. The young salmon use currents as escalators. They ride them for propulsion and add to this their swimming power. Recovered tagged fish showed that smolts’ swimming power was often equal to the speed of the ocean currents. They may be small but they are powerful.

Climate variability also affected where they went. Oceanic circulation round Scotland and the North Sea is anti-clockwise. It is also driven by winds, especially between March and May. As the climate alters, these winds have been strengthening and this affects marine growth and fish travelling in the upper layers, like smolts.

Smolts’ growth rate, as measured by SALSEA, is prodigious, fairly justifying the description ‘explosive’. Each day they might grow 0.6 per cent of their body length. At the southerly edge of Atlantic salmon range smolt survival is worst. Whether the young salmon were leaving the River Loire Allier in northern France and heading westwards round the Atlantic coast of Ireland to find feeding midway between Iceland and Norway in the Norwegian Sea, or leaving north-west Spain and negotiating the English Channel, southerly stocks struggled more. The impoverished Allier has only a bare-bones population of 500–1000 breeding salmon to start with, and the Spanish rivers are similar.