To the sea and back

Published: 14th June 2016

Sea trout once thrived in the rivers and sea around the Trust’s property at Strathaird on the Isle of Skye, but today it’s different

Fisheries biologist Peter Cunningham tells the story of Sea trout – and how the restoration of the species could fit within a wider vision of the future of the Trust's property at Strathaird on the Isle of Skye.

Sea trout are a form of brown trout (Salmo trutta) which, after three or four years living in freshwater, migrate to the sea where they grow faster. Sea trout can grow to 3.5kg (8lb) or more. In the west of Scotland, most are female fish, as many of their brothers remain in freshwater for their whole lives. In contrast to salmon, most of which die after spawning for the first time, some sea trout return from the sea to spawn in freshwater many times, and can live for over 10 years.

Within the John Muir Trust’s property on Skye, there are five notable stream systems that once supported prolific populations of sea trout. From the slopes of Sgurr nan Gillean, the Sligachan River flows north through a glaciated valley to enter the sea just beyond the iconic road bridge opposite the hotel. The river’s clear waters run over a streambed of stones – gabbro from the Cuillin – which appear turquoise-blue. Not so long ago, hundreds of sea trout gathered in some of the Sligachan’s pools during the summer months.

Elsewhere, the Coruisk, Camasunary, Kilmarie and Strathmore river systems flow into Loch Scavaig and Loch Slapin to the south. The once remarkable sea trout fisheries of these rivers were described by Stephen Johnson during his time in German prison camps after his fighter bomber was shot down in 1942. His notes were published in 1947; an angling classic, ‘Fishing from Afar’ (republished in 2004) remains one of my favourite fishing books.

From fry to ‘moonies’

Almost two years ago now, I visited Camasunary with fisheries owner Alan Johnson and family, and the Trust’s Strathaird property manager Ally MacAskill, to learn more about its fish populations. To survey juvenile fish, electro-fishing equipment was used. We found trout fry in the nursery stream above Loch an Athain and brightly-coloured salmon parr in the main river. From Loch na Creitheach, we caught samples of older trout using rod and line and a fyke net (with special permission from the Scottish Government and the Skye DFSB). Our catch of a dozen trout included four mature male brown trout and six sea trout – the largest, a female measuring 348mm (just under 14 inches).

In the past there were many larger fish. The Johnson family tradition is that any angler who catches a sea trout of 8lb or more should paint a life-size replica of the fish to be pasted on the wall inside the lodge at Camasunary. Until the 1980s, these big sea trout, called ‘moonies’ (after a ghillie had cursed one that got away) were caught at a rate of at least one per year.

I measured and photographed 78 moonies, caught between 1939 and 1983, each the product of a wildlife encounter as exciting and memorable as any that one might hope for within a lifetime (my largest sea trout to date is a 4lb fish caught when I was just 16!). For devoted followers of wild trout, Camasunary lodge is like a shrine: the 70-year artistic record of Camasunary and Coruisk’s fabulous sea trout provides a reminder of just how wonderful wild sea trout fishing can be. 

But sea trout are important for far more than just sport. For many of the animals of Strathaird, from otter and fox to rodents, raptors, other birds and many insects, the spawning runs of wild salmon and sea trout represent an important seasonal food source.

At sea, trout can grow quickly by feeding on sandeels, herring, and other small fish and crustaceans. And like salmon, sea trout provide a ‘trophic’ pathway, delivering nutrients of marine origin in the form of fish eggs and fish carcasses to otherwise oligotrophic (nutrient-starved) streams. In the past, marine-derived nutrients would have enriched the streams and lochs more so than today – a natural source of life-sustaining fertiliser within an otherwise leached and barren landscape.

At Strathaird, sea trout would have been an integral part of the ecosystem. During periods of abundance, sea trout may have sustained positive feedback loops, which amplify changes in the marine environment,  much like the salmon around the north Pacific. Juvenile trout and salmon gorge on surplus fish eggs at spawning time. The production of juvenile trout may have increased when there were many big sea trout providing surplus eggs, and  when larger amounts of marine nutrients in fish carcasses were recycled within the valley by people and other predators. 

Threats and uncertainties

Stephen Johnson’s ‘Fishing from Afar’ describes an abundance of sea trout around Strathaird not seen for several decades. Since the mid 1980s, sea trout have been subject to many pressures, including the collapse of inshore fish populations as a result of increased fishing pressure following the removal of the coastal ‘three-mile’ exclusion zone for trawlers in 1984.

Lawrence Court, a local angler I spoke with recently, tells an interesting story of a mass fish kill following night-time trawling (possibly dredging) just off Camasunary beach. “Three years ago we had a trawler in the bay at night and it turned its lights off when we put a high beam lamp onto it,” he says. “It was no more than 100-150 yards off the beach. The next morning there were tens of thousands of sand eels all dead on the beach. It was an incredible sight and very saddening.”

But inshore trawling is far from the only threat. For sea trout, infestations by parasitic sea lice associated with growth of the salmon farming industry have been a major cause of the collapse in stocks in the west of Scotland. As such, the future for Camasunary sea trout and those of other river systems within the South Skye sea lochs area (Loch Scavaig, Loch Slapin and Loch Eishort) remains uncertain.

The local community has objected strongly to recent planning applications for three huge (2,000+ tonne biomass) new salmon farms. If any of these farms are established, there is little prospect of a recovery in sea trout populations, given the salmon farming industry’s continuing inability to control sea lice populations. However, if the area can remain free of salmon farms, and other issues are addressed, prospects for the recovery of sea trout populations in the Strathaird area appear good, as the next nearest salmon farms (and major sources of larval sea lice) are 25 miles  away.

A further threat comes from predation, with high numbers of seals around Scotland. Seals (both grey and harbour) are often seen around river mouths when sea trout and salmon gather, while some grey seals also follow fishing boats to feed on discards.  Fostering the recovery of other inshore fish populations and reducing the amount of by-catch discarded at sea should help to restore marine ecosystems to a point where seals have a wider diversity of healthy prey.

Meanwhile, poaching also remains a problem. There is a tradition on Skye, almost a culture, of taking ‘one for the pot’. When stocks of salmon and sea trout were prolific, losses to poachers may have had little impact on fish stocks. However, in recent years, the numbers of adult salmon and sea trout entering some of the rivers on Skye have been barely adequate to produce the next generations of young fish. School-based education projects may help to change attitudes. Many anglers and fisheries currently practice ‘catch and release’ where a majority of sea trout and salmon are returned to enable them to spawn.

Ecosystem collapse … and recovery

From my vantage point by the side of Loch na Creitheach, the surrounding hillsides looked denuded and impoverished. My interpretation is that over many centuries, grazing and trampling by cattle, sheep and deer have exacerbated vegetation and soil loss and leaching, degrading the productive potential of the Camasunary valley.

Although the underlying geology of the catchment area includes base-rich rocks (and their influence on vegetation can be seen on the slopes of Blaven) there is little food for juvenile fish in the nursery streams. There are virtually no trees, and few bushes to provide leaf litter to feed some of the insect larvae upon which juvenile trout and salmon feed. The loss of vegetation (especially larger plants), breakdown of ecological processes and trophic pathways connecting different parts of the ecosystem have led to biological impoverishment. This has been exacerbated by the export of nutrients contained in cattle, sheep and deer carcasses outwith the catchment, plus soil erosion. 

To successfully restore wild sea trout and salmon populations, a Skye-wide initiative is needed. The current generation of children on the island are missing out on something their forefathers took for granted. Restoration of sea trout populations and ecosystem fertility requires a change in the management of both the land and the waters surrounding the island.

Perhaps there are opportunities to develop some sort of initiative at Strathaird? Could a joint project between the John Muir Trust, the crofting community, other local people and wildlife and fisheries interests, be a way forward for the Camasunary valley, for the benefit of all?

Some things are clear. Soils need to be redeveloped where eroded away. Roots of trees and scrub can bind screes and other fragile slopes to reduce rates of erosion. However, it’s not just about planting trees and controlling grazing pressure. Look carefully: nutrient hotspots around bird and mammal perches and otter spraint sites support vegetation richer in phosphorus and other minerals than the surrounding ground. Why not focus upon these natural biodiversity ‘oases’, and develop a fertility mosaic to replace the missing nutrients and restore life within the landscape?

Like feeding the birds, I’d recommend supplementary application of bone meal fertiliser (or a similar phosphate rich fertiliser) at rates which mimic those that would have occurred when salmon and sea trout were much more abundant and the ecosystem was in better health. And to address issues within the marine environment, could the nearby Small Isles Marine Protected Area be extended to foster recovery of seabed habitats and wild fish populations, including sea trout, in the waters around Strathaird?

Two years on from my visit, I remain just as excited about the prospects of restoring sea trout populations and revitalising the area to bring benefits to the lives of many. That’s my vision for the future of Strathaird.

About the author

Peter Cunningham works as biologist for the Wester Ross Fisheries Trust which, in recent years, has carried out surveys of fish populations in Skye in support of the Skye Fisheries Trust. Peter can be contacted at info@wrft.org.uk

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