Sea trout are brown trout that migrate to sea. Brown and sea trout are
the same species
(Salmo trutta). Some brown trout migrate to sea and some sea trout
eggs develop into brown trout that remain in the river throughout their
Scientists have not yet worked out why some trout migrate to sea. It is possibly an interaction between genetic and environmental factors. Maybe a lack of food in the river triggers migration. We do know that the better sea trout rivers tend to be short acidic rivers with easy access to good spawning and nursery areas.
Most sea trout are female . They produce an average of 800 eggs per pound of their body weight. Clearly migratory trout make an important contribution to trout stocks. The heavier, older sea trout produce more and larger eggs, and should be released for the sake of conserving the stock of trout in a river.
The ‘First International Sea Trout Symposium’ in 2004 highlighted the following key points:
Diagram shows the life cycle of sea trout.
From the Celtic Sea Trout Project
This fly was fished at night after treatment with floatant so that it fished in the surface and created a wake when retrieved
This fly was fished as a dry fly or nymph during the day. It went through several versions with increasing amounts of red / pink dubbing
At the "2nd International Sea Trout Symposium" held in 2015 it was reported
that a study on the Shimna river in Northern Ireland revealed that 85%
of eggs in the river were contributed by larger sea trout that had spent
at least one winter at sea.
This shows how important sea trout are for maintaining healthy trout stocks.