The men, a 22-year-old and a 49-year-old from Caerphilly, were apprehended near Draethen, at around 4.30pm on 19 January, after they were reported by a member of the public.
The officers seized one salmon which had been taken by the men, along with a rod, net and other fishing equipment which were believed to be connected with the alleged offences.
Fishing out of season has a serious impact on salmon stocks in rivers and an impact on angling tourism and the local economy.
Rhys Hughes, Environment Agency Wales, said:
“Poaching at any time of year significantly threatens the future stocks of salmon in the River Rhymney.
We appreciate the assistance we receive from legitimate anglers to report any such activity and we urge anyone who sees suspicious activity to call our Incident Hotline on 0800 80 70 60.”
