This video says about itself:
14 December 2009
Three sea trout spawning in December 2009 on a small stream tributary of the Sussex Ouse. There are two larger fish in the redd spawning (a male and a female up to about 8lb) and also a smaller chancer male about 40cm downstream of them. When the larger male is not so active the smaller one darts in and tries to fertilise the female’s eggs, and is then usually seen off by the larger male.
By Dave Bangs in England:
Another native species under threat
Thursday 5th January 2017
Sussex’s native sea trout have returned to Britain’s freshwater rivers and streams since before the last ice age, yet their habitats are being destroyed, writes DAVE BANGS
I should explain that the sea trout is a particular type of our native trout species which leaves its birthplace in our little streams to roam the sea before returning to its natal stream to spawn.
Many of its close relatives choose to stay all their lives at home, however, and they are known as the brown trout or “brownies.”
They tend to be much smaller because their freshwater diet is poorer than a sea-going diet.
Our Sussex sea trout can be as big as salmon and spawn later than other races of their kind.
You find their gravel nests around Christmas time, especially in our chalk streams.
At deepest dusk, if you are lucky, you may see a giant “hen” fish lying in the scrape she has dug, whilst the “cock” fish sidle up to her to mix their milt (sperm) with her roe (eggs).
Their backs emerge from the shallow riffles like surfacing submarines, whilst the water breaks over them.
In their breeding finery they are spotted brightest pink and black and grow to 2.5ft long and over 12lb in weight.
These fish have probably been returning annually to our local rivers from their rich sea feeding waters since long before the end of the ice age some 12,000 years ago.
Their migrations have marked the retreat of glaciers and tundra and the greening of our 30-mile wide Wealden vale to the lush “salad bowl” of trees and meadows that it is today.
Things are not good for these ancient beasts, however, whose numbers may be counted nowadays in the hundreds rather than the teeming thousands of the deep past.
Obstructing weirs have been built along most streams to facilitate farmers’ irrigation and commercial navigation, to make mill ponds, and manage coarse fisheries.
Sewage works and farmers’ pollutions periodically plague the rivers.
As the human population of the south east of England swells in response to capitalism’s unequal regional development new housing requires more and more freshwater, and the head streams shrivel and dry back towards the Rivers Adur and Ouse main channels.
Only the perennial springs along the base of the South Downs scarp give certainty of flow to the crystal clear chalk streams.
There is however no certainty about the future of those streams either.
This year a “posh food” business sought to bring another rare species — Siberian sturgeon — to the meadows next to a sea trout nursery stream of the Ouse, to stock the newly dug ponds of a “caviar farm” (caviar is sturgeon eggs) bringing new risks to the precious water supply of these streams, breaking the open riparian corridor and threatening new biosecurity measures and exclusion fences.
The residents who led the campaign against the fish farm were a cross section of our modern countryside: rich bankers and business millionaires.
Their campaign slogan: “Wrong Fish, Wrong Place,” attracted sarcastic responses from those urban folk who felt the sturgeon farmer was not the only person whose entitlement to this countryside they wished to challenge.
We won that time, despite the social narrowness of the campaign and Lewes district council rejected the fish farm’s planning application.
Yet within a few days, far worse disaster struck.
At dead of night a system failure at the dairy unit of nearby Plumpton Agricultural College emptied the contents, it is estimated, of a whole slurry tank into the headwaters of the Plumpton Mill Stream.
A kilometre-long “slug” of ink-black dung and urine rolled down into the Bevern stream and along to the confluence with the River Ouse at Barcombe Mills.
In one night, the streams which the Ouse and Adur Rivers Trust had been working to conserve for 30 years were stripped of their higher life forms.
It may take another generation to restore them.
This is not the first time Plumpton College has polluted our streams. Anglers and river workers report pollution incidents back as far as they can remember: nine incidents just since 2011.
Day and night, the workers of the Environment Agency struggled to contain the pollution with sandbags, oxygenators and water pumps.
But the damage had been done.
Will the magnificent beasts of these little streams survive beyond our time?
That is up to us. It is not up to millionaire rural residents and businesses. It is not up to polluting private rural colleges.
It is up to us — from our towns and cities — to reclaim and restore our natural heritage.
USA: A multi-institutional team of researchers has assessed how environmental, demographic, and genetic factors play a role in the reintroduction of bull trout in Washington State: here.