Dozens of dead fish washed up as a result of a river pollution incident has alarmed MP Simon Hart.
The River Gwynddo which runs through Llanmill near Narberth has been turned into a murky green torrent and dozens of dead fish have washed up.
"When the fish die the river dies with them," said Mr Hart who is a keen fisherman. "It has been running brown for about 18 hours and it will take an age for the sensitive biodiversity to recover."
The river runs close to Mr Hart's home in Llanmill and is a tributary of the River Marlais that runs through Lampeter Vale. It recently attracted hundreds of birdwatchers from all over the UK who travelled to visit a rare green heron that visited the stream.
Mr Hart has been lobbying the Welsh Assembly Government to make Natural Resources Wales enforce more strongly the rules regarding river pollution.