Delighted Broads anglers are hailing a report by researchers at the University of East Anglia on the health of Norfolk's famous wildlife reserve as the strongest evidence yet that the debilitating effect of man-made pollution is steadily being mastered.

But within hours of publication of this optimistic survey at the UEA's School of Environmental Sciences came a stark reminder that Mother Nature can still deal this revered national water park a potentially deadly hand as toxic saline was driven miles inland by a stormy North Sea tossed up by a fierce north-westerly blast.

Fortunately, on this occasion, the Spring tides had built up slowly and by the time the salt water content at Acle on the river Bure had reached a lethal 95pc the great shoals of bream and roach had fled upstream to safety while the plug of pollution retreated on the ebb tides.

Environment Agency Fishery officers were on the case, taking action 24 hours before the sea had topped the flood defences at Walcott, closing the road.

The barrier that stops sea water spilling into the Potter Heigham boat lagoons, where many thousands of fish overwinter, was raised and in place as soon as the flood warnings went out.

Fish populations in the lower tidals of every river appear to have settled in safe waters at Horning on the Bure, Martham on the Thurne, Postwick to Bramerton on the Yare and in the Wensum in the heart of Norwich, with catches rising well in to double figures at all of these venues.

The EA's field officer Steve Lane ended his tour of the area checking for salt water casualties with a reassuring report.

'So far I've seen just one dead skimmer bream in the Acle boat dyke and at present I do not expect to discover serious fish mortalities caused by this event,' he said.

This news came as a great relief to match anglers, who have been enjoying something of a renaissance on the tidal river Thurne where bream and roach nets have consistently topped the 20lb mark.

Mick Brown, who runs the Wednesday open events below the Martham boatyard, said today's event would definitely go ahead and he expected extra fish in the match stretch if saline had penetrated as far as Potter Heigham.

'Provided we do not get hard frosts I think we can expect some very fair catches for the remainder of the year,' he forecast, while adding his voice to the many demanding the protection of a tidal barrage at Great Yarmouth.

Back to that UEA audit of the Broads burgeoning biodiversity – this in-depth survey revealed that once endangered species like the otter, the bittern, the marsh harrier and even the stately heron had retreated from the brink of extinction and were thriving among 11,000 indigenous species in the Broads, 31 of which are seldom seen anywhere else in the United Kingdom.

While the news that fish eating predators appear to be more than holding their own in the Broads will not be welcomed by the 'let's cull them' tendency the latest statistics are accepted as encouraging by the great majority who understand that coarse fish have always provided a main source of protein for birds and mammals and even man.

Tony Gibbons, the Norwich and District Anglers chairman and Broads consultant, commented 'The UEA survey confirms that fish stocks on the Broads have reached a level where they can support predators as well as anglers. We can see a natural equilibrium that has not seemed so clearly apparent since the end of the Second World War.'

'Frankly, I think we have heard enough of these silly attempts to persuade the government that we need to cull otters and other native fish eaters. Pike eat fish, but bream and roach anglers are not forever banging on about it because we believe there are sufficient fish for all of us.'

• The famous river Thurne river system continues to relinquish specimen pike, the latest a 28lb beauty for Great Yarmouth angler James Smith.

The 29-year-old, fishing the Martham area of the Thurne, tempted his PB on a dead roach as the light was fading.

Piking prospects are rated excellent throughout the Broads, with other hotspots the river Wensum in Norwich, the river Yare from Trowse to Postwick and the river Bure below Wroxham bridge.