A by-law imposed by the Welsh Assembly banning the landing of salmon and sea trout on the River Wye has been welcomed by the head of the river's watchdog, Dr Stephen Marsh.
The by-law brought in this week forces anglers to return any salmon and sea trout caught to the river, or face a heavy fine.
It is hoped the new legislation will boost declining numbers of the fish in the Wye, which runs from the mountains at Plynlimon in Wales to join the mouth of the river Severn at Chepstow.
Dr Marsh says that salmon numbers in the Wye have actually been recovering for a decade, but welcomed the law as "better late than never".
"If we had done this ten years ago, we might be looking at removing the restriction now," Dr Marsh told the BBC.
The Environment Agency was keen to stress that the law was targeted at the small minority of fishermen who take fish away from the river. This prevents them from spawning upstream and has a serious effect on numbers in future years.
Pete Gough works for the Environment Agency.
"The majority of anglers are very responsible and do release the salmon and sea trout they catch. However, there are some that continue to kill the fish before they have a chance to spawn upstream," he told the BBC.
The law comes in the wake of moves made by the Wye and Usk Foundation to improve the numbers of salmon and sea trout in the river. The Foundation has installed fish passes along the river's length, and has removed barriers to make migration up its course much easier.
The Wye used to be one of the best salmon fishing rivers in Europe but a sharp decline in numbers to 2002 forced action. Since then numbers have actually been on the increase.
Dr Marsh told the BBC: "This year is very much a recovery year. We are seeing encouraging numbers of very big fish."
The angling industry on the river brings around £5m of businesses into the region each year, but Dr Marsh believes this number should be at least double if fish numbers in the river were improved further.