Officers from Natural Resources Wales have searched a premises in the Gilfach Goch area after receiving information about suspected fisheries offences.
The search warrants were supported by South Wales Police.
Whole and parts of ‘unclean’ female sea trout were found as a result of the search, ‘unclean’ meaning they were in the process of spawning or about to spawn.
One of the recovered sea trout was estimated to be carrying between 4000 and 5000 eggs representing a potentially large contribution to the next generation of fish.
Salmon and sea trout migrate between feeding grounds at sea and freshwater habitats where they spawn in winter months.
Two males aged 27 and 57 have been reported for handling fish in suspicious circumstances and having ‘unclean fish’ in their possession as a result of the investigation.
Erin Smyth, Senior Environmental Crime Officer with Natural Resources Wales, said
“Sea trout, or sewin, are iconic species in our rivers in Wales and they attract anglers from across the world - bringing a much needed boost to the rural economy.
“With the fish numbers in our rivers already low, we have to make sure that every fish is given the opportunity to spawn and help boost future populations.
“If anyone has any information of illegal fishing or fishing out of season we urge them to report it to our hotline on 080 80 70 60 so we can investigate.”
NRW’s salmon stock assessments now show an ongoing decline across Wales, with sea trout stocks also giving cause for concern. 40% of the 33 main sea trout rivers in Wales are at risk of not having enough fish returning to their spawning sites to maintain future populations.
Possession of fresh salmon or sea trout after the 17 October would most likely be unlawful as the fishing season is between March and October to allow these fish to spawn.
The fishing season for salmon and sea trout doesn’t start again in Wales until March 2016. Anyone with information about fish being taken during the winter months is asked to contact NRW via the incident number on 0800 807060.