---

---

---

---

Science Current Events and Science News RSS Feeds

---

---

Email a Friend Printer Friendly

Cardiff barrage is blocking out migratory fish

June 19, 2002

EMBARGOED UNTIL WEDNESDAY 19 JUNE 2002 19:00 BST
UK CONTACT - Claire Bowles, New Scientist Press Office, London:
Tel: +44(0)20 7331 2751 or email claire.bowles@rbi.co.uk

CARDIFF bay barrage, centrepiece of Europe`s largest waterfront development, could cost British taxpayers more than they thought.
        The barrage stretches across the bay, creating a false harbour. But it also blocks the route of fish migrating up from the Severn estuary into two Welsh rivers that flow into the bay. Now the Environment Agency has told New Scientist that a fish pass, which is supposed to let them through, is not working properly, and the public may have to shell out hundreds of thousands of pounds to replace spawning salmon.
        "Every adult salmon that doesn`t make it up could cost thousands to the taxpayer," says Rhys Morgan of the Environment Agency, who monitors the barrage.
        
Controversy has dogged the barrage project. Completing the barrage in 2000 created a 200-hectare freshwater lake that has been the catalyst for a massive redevelopment of Cardiff`s disused docks. But the tidal bay the lake replaced was a vital feeding ground for wading birds. It was designated a protected Site of Special Scientific Interest, and before the go-ahead, no SSSI had ever been destroyed to make way for a public development project.
        
Now it seems that there are problems with the fish pass that allows migratory fish such as salmon and sea trout into the South Wales rivers to breed. Morgan says design flaws have closed the pass for weeks on end. If this happens when the fish return, they won`t queue up and wait to be let in, he says.
        
Roger Thorney of the Cardiff Harbour Authority, the public body that manages the barrage, says these closures were just "teething problems", and that the barrage is now working at 95 to 100 per cent efficiency. But Morgan says there are still problems with the flow rate of water through the pass. To attract fish, the structure must allow enough water into the estuary to maintain a plume of fresh water there. The velocity of the water is crucial: too strong and the fish can`t swim against it, too weak and they won`t find it.
        
Last year fewer than 300 fish made it upriver. This is more than 60 per cent down on the average for the previous 11 years, says Morgan, although he says that fish numbers vary considerably so it is too early to say whether the barrage is responsible.
        
But Morgan says that if the problems aren`t corrected by the time monitoring ends in 2005, the public will have to pay. If fewer than 1000 adult salmon a year return to the rivers that flow into the bay, the harbour authority will have to pay £400 to replace every fish that doesn`t make it. "They don`t seem to realise the enormity of the mitigation and the fact that this could go on forever," says Morgan.
Author: James Randerson

New Scientist