The barrier at Herbert Woods boat yard in Potter Heigham, Norfolk Broads, is raised when surge tides are expected. This is to prevent salt water from entering the boat yard where shoals of freshwater fish, which gather in the boat yard during the winter, are protected from salt water.
Earlier this week Environment Agency teams carried out salinity tests in parts of the Broads system and as levels of salt were high, the barrier was shut on Monday.
Officers then used a specialist underwater sonar camera to assess the fish numbers in the boatyard and it is estimated hundreds of thousands of fish had sheltered there. The barrier was re-opened today and no fish deaths have been reported.
Steve Lane, fisheries technical specialist, said:
If we had not closed the barrier, there is no doubt we would have had to carry out a significant fish rescue and it is likely there would have been some fish deaths. Thankfully Environment Agency teams worked together to take action when this salt water surge occurred.
We are continually grateful to Herbert Woods boat yard for their assistance and understanding in operating the barrier, and also to the private boat owners for their co-operation and help to protect the fish. We would also like to thank the anglers who have been out checking in the last few days to see if there have been any fish in distress.
The Environment Agency uses water quality monitors called sondes to track the salt as it moves up the river, thereby giving them enough time to raise the barrier.
During September to March, it is more common to see surge tides push saltwater into tidal rivers and with the added factor of strong winds, this can mean an influx of salt water infiltrates the boat yards and dykes, trapping the fish.
If you see any fish in distress, call the Environment Agency incident hotline on