SEA TROUT - TAILS IN THE RIVERBANK | | An amazing underwater tale of a tenacious fish |
Chris Packham uncovers the hidden world of the New Forest streams with the Environment Agency Fisheries team. The New Forest rivers are of international importance and home to an extraordinary number of species from the primitive Brook Lamprey to the freshwater equivalent of the shark - the fearsome Pike. Each year they also witness an amazing spectacle - the spawning of the Sea Trout.
Sea Trout are in fact Brown Trout that have decided to take to the sea. Incredible life-cycle | | Dominic Longley, 'within a 100metre stretch, we've seen 10 or 12 different species' |
But every year they return to the rivers to spawn at almost the same spot where they were born.
These impressive fish can reach 31" (78cm) in length and weigh anything up to 20lb (9kg) and yet they make their way through shallow water to the tops of the forest streams. The sea trout only return for a few weeks each year and despite their size remain largely unnoticed.
The female - or hen fish - creates a shallow depression in the river bottom known as a redd, in which she lays her eggs. She does this by thrashing her tail in the gravel. Dominic Longley, a fisheries officer with the Environment Agency, told Inside Out, "The Sea Trout is a creature that has managed to go through this incredible life cycle unseen.
 | | A classic male or cock Sea Trout from the Lymington River |
"You even speak to local people and a lot of them are completely unaware of their existence.
"They're a low profile creature and it makes it even more amazing that you see a small tributary of a river in the New Forest and see these enormous ocean going fish spawning with barely enough water to cover their backs and when you see that in the depths of winter in the middle of a woodland it's quite astonishing." The Environment Agency is responsible for monitoring the wildlife in the forest streams. The slippery Eel Each year they survey the rivers by sending an electric current through the water that stuns all the creatures close by. They then measure and weigh them and take scale samples from which they can learn the life history of each fish.
The fish are then returned unharmed. Inside Out filmed the agency electrically stunning a 100 metre stretch of the Lymington River which produced almost a dozen different species including Eels which have the most amazing life cycle.
They are thought to spawn in the remote Sargasso Sea in the middle of the South West Atlantic.
The animals then drift back in ocean currents before entering freshwater rivers where they remain for anything up to 50 years before returning to the sea. | 
