Atlantic Salmon, can grow up to 1.2-1.5 metres and weigh up to 40 kilograms and can live up to 13 years, it is found in the cleanest rivers, mostly in the north and west. It spends most of its life at sea, but returns to spawn in the same stretch of river or stream in which it hatched. Travelling upstream from November to February, Atlantic Salmon can be spotted jumping over weirs and waterfalls to get to the gravelly headwaters where they breed. Once they have reached their breeding grounds, the females dig depressions, known as ‘redds’, in the gravel; the eggs and sperm are released simultaneously into the water. The juveniles will stay in freshwater for up to six years, after which they migrate back to the sea. Atlantic Salmon are predators, feeding on invertebrates and small fish.
Adult Atlantic Salmon are much larger than trout; they are silvery with a few dark spots on the back and may have a pinkish flush to the belly. Mature males may develop a hooked lower jaw, or ‘kype’, in the breeding season.
They are found in rivers in Wales, Scotland and North and South West England.
Known as the ‘King of Fish’, the Atlantic Salmon is able to clear seemingly insurmountable obstacles during its journey to spawn: from waterfalls to weirs, Atlantic salmon have been known to leap vertical obstacles more than 3 metres tall. However, these obstacles take energy to pass, and man-made barriers to migration are considered one of the most pressing threats to our salmon populations.
It is unclear how Atlantic Salmon navigate to the breeding grounds of their own hatching, but it is thought that smell is important when they are in fresh water and that the Earth’s magnetic field plays a part when they are at sea.
The River Ehen is principally a migratory salmonid river. Although catches of salmon and sea trout have been very good historically, current catch levels are now significantly lower than previously recorded and runs of adult salmon back into the river are of prime concern at present (2018). The underlining issue with salmon stocks is very poor marine survival which appears to be having a disproportionately negative impact on one-sea-winter “grilse” which have historically formed the bulk of the River Ehen salmon run. This decline is also of concern with regard to the mussel population as they are dependent on salmon as part of their lifecycle.
There is also a small population of resident brown trout in the River Ehen, while Ennerdale Water and its tributaries contain an important population of brown trout and the most significant extant population of river-spawning Arctic charr in England and Wales.
The EA requires that all salmon and sea trout anglers return detailed records of their rod catches each year.These rod catch data include all rod caught salmon and sea trout along with whether or not they were released back into the river.
The River Ehen salmon population is considered to be “Probably At Risk” (2018) and is predicted to remain so in five years’ time, based on an assessment of estimated egg depositions over the last ten years (2007-2016). These data show that the stock as a whole has remained above its Conservation Limit in most years but fell below it in 2015 and only just exceeded it in 2016. The overall trend in salmon egg deposition in the River Ehen is now downwards.
Conservation Limit is the minimum level of egg deposition that is desirable in a catchment in order to maintain it at a sustainable population (catch) level. This limit is based on an assessment of the naturally available spawning habitat within the Ehen catchment including all relevant tributaries. Annual egg deposition estimates are then calculated from rod catch data each year and compared to this Conservation Limit to determine how healthy the overall population is.