Nature notes

Secret life of mountain fish

You might not know this, but 2019 is the International Year of the Salmon. Bearing this in mind, it feels like the perfect time to think about all things fishy in the mountains.

Up in the hills, fish are as much part of the landscape as they are lower down in the valley. We all know the salmon. But were you aware of the complexity of its lifecycle? Its eggs are laid between November and January, on a gravelly, well-oxygenated stretch of stream bed. Come spring, the eggs hatch into fry. After a few weeks the young salmon, now known as a parr, develops stripes (for camouflage) and spends up to three years growing in the river where it hatched. The lure of the sea is strong, and the parr becomes a smolt once it has made the transition into salt water.

Maturity is reached after about a year at sea, and it then becomes known as a grilse. During its time at sea, the grilse can migrate up to 3000km to the Arctic Circle in search of food-rich waters. But the urge to procreate draws the grilse back to the very stretch of stream where it hatched. This journey is fraught with danger, as everyone wants a piece of the action. Humans, most of all.

Once it has made it back, the young salmon holes up until the winter when it eventually spawns, thus completing this miraculous cycle of nature. A spawnedout salmon is known as a kelt, and some may survive to repeat this cycle, but the majority perish. Next time you’re lucky enough to see ‘running’ salmon in a mountain river, spare a thought and look on with admiration as this scaly globetrotter comes home.

Some relatives of the salmon live their lives in the same place, while others are migratory. Similar to the salmon, the Arctic char is a much scarcer British fish. Frequenting cold, clear lakes and lochs, feeding on planktonic crustaceans and molluscs, it’s a reminder of much icier

times. Smaller and incredibly rare is the vendace. A slender, silver fish, it is believed only to live in the Lake District’s Derwent Water and one or two other lesser-known spots. It needs nutrient-poor, deep, clear water, and fertiliser-rich run-off from surrounding fields is suspected to be a major contributing factor in its decline.

Suffering similarly is another delicate plankton feeder – the powan, as it’s called in Loch Lomond. Considered the poor man’s herring, it was known as the skelly in the Lake District and gwyniad in Wales. The brown trout completes the list of mountain fish. With flanks covered in leopard-like spots, this beauty is much prized by anglers. Why do such vast, brutal bodies of water contain such delicate inhabitants?

From above all fish appear dull, as this helps to avoid the attention of predators. Loons, ospreys, white-tailed eagles, otters – all are rampant fish killers. Unlike us, they take only what they need, while we kill indiscriminately with our fertilisers and controlling ways, hence the need for an International Year of the Salmon. The project aims to raise awareness of salmon conservation in the northern hemisphere.

The next time you lunch or camp by a tarn or mountain stream, take a moment to imagine that other world in the cold, black depths. Follow the contours of the surrounding hills down below the water’s surface to get an idea of what the underwater topography is like. It might just be home to some of the fascinating species mentioned above.

tom Bailey is an outdoor writer, nature expert and long-serving trail magazine photographer.