A new salmon law is being proposed that could ban anglers from taking their catch home.
The Environment Agency proposed the measure and said it was needed to protect salmon stocks that are in decline. Consultations are under way.
If the by-law was introduced it would apply to salmon fishing along the length of the River Severn.
The Severn Fisheries Group, which represents 30,000 anglers, said that might encourage more poaching.
Group co-ordinator Glyn Marshall said: "Anglers are the eyes and ears on the river. If they're on the river they watch over the river.
"What will happen is anglers will disappear, illegal fishing and poaching will increase massively and more salmon will be killed."
The proposed law could apply for a decade with a review after five years.
It would restrict fishing methods to improve their chances of survival and would require any salmon caught to be released back into the river.
The Agency said it wanted to work with anglers in finding the best way forward.
Kevin Austin, from the Environment Agency, said: "The decline in the numbers of wild salmon seen not just in English rivers but throughout the North Atlantic is of great concern and we are determined to protect the future of this important species.
"We must all work together to successfully protect this iconic fish for future generations."
The Environment Agency is also looking at other methods to protect salmon including improving water quality and encouraging better farming practices.
The consultation closes on 6 April.