The fish was caught on the River Dee near the border with England in Chester.
NRW is asking netsmen and anglers to report any unusual catches.
Despite this being a Welsh first, numerous reports of captured pink salmon were made around the UK in 2017 with the majority being caught in Scotland.
David Mee, specialist fisheries advisor for NRW, said: “It is quite unusual to find pink salmon in our waters, this may be the first in some 30 years, though there were numerous reports around the UK and Ireland in 2017.
“I’d urge netsmen and anglers to contact us if they see any non-native salmon in the waters, with a date, location and, if possible a photograph, which would really help us identify them and build up a picture of where they may be.”
Pink salmon, also known as humpback salmon, originate from the northern Pacific Ocean.
It is believed the fish made their way to northern Europe after being introduced commercially to Russian waters.
The appearance of the species is of concern as it may impact on Wales’ indigenous salmon and sea trout populations in the future.
Source: BBC News 8th August 2019