Having spent up to five years in the food-rich waters of the north Atlantic and Arctic, adult wild salmon are now ascending the rivers of their birth to spawn.

A combination of earth's magnetic field and probably stars, guide their progress in the ocean and direct them southwards towards the coast.

Arriving there, a chemical 'memory' of smell and taste takes over to steer the fish to their correct rivers.

Once in the estuary they face many hazards from porpoises to seals, predatory fish and commercial nets.

Thankfully, the latter are fewer nowadays as a result of conservation legislation and an abundance of farmed salmon for the table.

Once in their hereditary rivers they change colour from silver to bright tartan hues and join other salmon known as 'springers' that began their journey to spawn earlier in the year.

Having fattened up in the ocean, feeding on krill, prawns and sand eels they do not feed in the river.

Making their way upstream negotiating weirs, waterfalls and otters, they eventually arrive at the spawning grounds.

By now, the lower jaws of males have grown upwards to form a 'kype' (pictured) used to fight rival males in the shallow oxygen-rich upper reaches.

With male and female side by side, spawning takes place within a shallow depression or 'redd' scooped out by the female.

The sticky eggs adhere to the gravel, then spawning completed, the fish replace the gravel to cover the eggs.

Next spring eggs will hatch and fry develop into 'parr' that remain feeding in the river for up to four years before becoming silver coloured 'smolts; which form shoals, swim to the sea and begin their complex life cycles over again.