A fisherman who had to limit the number of salmon he was allowed to catch must be compensated, a court has ruled.
Nigel Mott, of Stroat, Chepstow, had fished near Lydney in Gloucestershire with a traditional putcher rank - basket-like traps - since the 1970s.
In 2012 the Environment Agency told him he could only catch 30 wild salmon per season in the estuary.
The Supreme Court ruled the agency gave no consideration to the "severe" impact on Mr Mott's livelihood.
Mr Mott challenged his licence conditions for 2012, 2013 and 2014, limiting his catches respectively to 30, 23, and 24 salmon each year.
He said before the limit was introduced his average catch using the rank was some 600 salmon per year, at a value of about £100 each, giving him a gross annual income in the order of £60,000.
Mr Mott argued the catch limit conditions have made his fishery "wholly uneconomic", saying the lease was "worthless", and alleging "irrationality" and a breach of his human rights.
A judge at the Supreme Court, in London, said the agency could not have properly imposed the conditions, if otherwise lawful, without payment of compensation, according to the European Court of Human Rights.
Speaking after the hearing Mr Mott said he was "very pleased with the verdict" but added his fishery remained "uneconomic".
"It's more of a shame for future generations than it is for me because the fisheries at Lydney were something that made Lydney a little bit special and different."
The Environment Agency said it accepted the court's ruling and would work with Mr Mott to agree appropriate compensation.
It added salmon stocks are at an all-time low and said it was working hard to restore them to healthy levels.