Brown Trout (Photo: Laurie Campbell)
At least four different forms of trout can be found in Harris. These are all the same species, but they have different life strategies.
1) Brown trout are the most common. They have lots of spots on their sides and are found in our lochs and burns.
2) Sea trout are the favourite of anglers. Like salmon, sea trout turn silver and visit the sea for richer feeding.
3) Slob trout hang around near beaches and in places where our rivers meet the sea. They don’t travel far and are intermediate in appearance between sea trout and brown trout.
4) Ferox trout are monsters of the deep and are quite rare. Ferocious ferox can weigh almost 15 Kg and cruise the big lochs hunting other fish.
Sea Trout (Photo: Laurie Campbell)
Our Scottish trout have been taken all over the world, even to America and Australia, for people to fish. Sometimes they have turned into a pest because they eat the local types of fish that live in those countries.
Trout have an amazing range of colours, life styles and shapes to suit the different waters they live in. Trout are found in the huge River Clyde which flows through Glasgow and the tiny burns in the Harris hills.
Big trout live on their own. They fiercely guard a good piece of water (often a deep dark pool) and chase other trout out.
Trout are related to salmon and their life cycles are similar. In places where there are not many salmon male salmon may occasionally spawn with female trout. Their progeny are then trout-salmon hybrids; they can have tails like a salmon and spots like a trout!
Trout like to eat flies that have fallen into the water. Anglers use feathers to make artificial flies and trick trout into biting their hooks. Some of these flies have funny names like Brown Buzzer and Muddler Minnow.
Muddler Minnow Fishing Lure (Photo: http://www.czechnymphs.co.uk/)
Life cycle and habitat
Trout are all born in freshwater but they can have lots of different life-styles. We are not sure why some trout go to sea while others stay in our rivers or lochs, but populations adapt to make the most of available feeding and spawning opportunites.
When they are at least three years old all trout gather to spawn in the same streams where they were born. This happens late in October and early November. Good places to build a redd and spawn have a gravelly or pebbly river bed and a fast flow of water to bring fresh water and oxygen to the eggs. Having paired with a male and chosen a suitable spot, the females turn on their side and powerfully flex their bodies and tails propelling jets of water that can displace stones. Gradually the female fish produces a depression in the river bed which is called a 'Redd'. The female deposits her eggs in the redd and the male fertilises them with milt. Then the female covers the eggs with clean gravel. Clean gravel is important, it allows fresh oxygenated water to reach the eggs but prevents the eggs from being washed away during spates and hopefully hides them from predators. After about six weeks little trout, called alevins, hatch out of their eggs and live in the gravel. Like salmon they have a handy pouch full of yolk and do not need to find any food until it runs out.
Brown Trout Alevin with Yolk Sac
When their yolk is used up alevins come to the surface of the gravel and begin to eat tiny water animals. They like to live in rivers and streams where the water is fast enough to make waves (these places are called riffles). As they grow alevins change shape to look like small adult, they are called fry and eat very small water animals.
Brown Trout Fry (Photo: Chilterns Chalk Stream Project)
After a year fry have new colours and eat bigger water animals and even small fish such as young sticklebacks. They also like to eat flies that have blown into the water. Young trout are now called parr.
Brown Trout Parr (Photo: Don Stazicker)
When they are young trout stay in groups and hide from big fish that might eat them. Adult trout are too big for fish to eat they stay alone and fight with other trout for the best pool in the river.
Sea trout and slob trout
Sea and slob trout are only found in lochs, rivers or burns that flow to the sea. Their life cycle is the same as brown trout until they are about three years old some of these trout turn silver and are called sea trout smolts. Smolts swim down their rivers and out into the sea where they feed on shrimps and small fish like sandeels. Some sea trout come back to freshwater after less than a year but others may stay at sea for up to five years.
Slob trout are not really sure what to do! They live in estuaries where rivers meet the sea and move in and out of freshwater whenever they fancy. Slob trout are a funny bunch, some are silver like sea trout and others are dark brown the colour of old seaweed. You might see sea trout and slob trout in pools on the sandy beaches of Harris. No matter where they travel at sea, sea trout and slob trout always come back to freshwaters to have their young.
Ferox trout are quite rare but you can find them in deep lochs like Loch Langabhat in South Harris. Ferox trout are born and grow up like brown trout but they specialise in eating fish. They especially like to eat young charr but are also cannibals and will eat other trout. Ferox trout look quite strange. They have big heads with big mouths for eating other fish.
The importance of trout to Harris
Trout are our most common freshwater fish and this makes them very important for everything that lives near freshwater. Lots of Harris animals like to eat trout including herons, cormorants, otters and eels. Sea trout are also food for marine animals such as cod, seals and dolphins. Even humans like to eat trout and enjoy fishing for them. People come on holiday to Harris from all over the world especially to go fishing for our plentiful wild trout.
Trout are also important to pearl mussels. These mussels are very rare. Baby mussels reach their home by sticking onto small trout or salmon and letting go when they get to the right spot, just like catching a bus.
by Katherine Ross