The Norwich and District Anglers' Association (NDAA) is requesting a voluntary keep net ban on all its waters when the new coarse fishing season casts off on Saturday.

The measure has been introduced to try and restrict the spread of the alien killer shrimp (Dikerogammorus Villosus) discovered in Barton Broad in the River Ant valley earlier this year.

Already known as the 'pink peril', this voracious crustacean attacks aquatic protein food sources, including fish spawn and newly-hatched fish larvae.

Environment Agency fishery experts fear this one-and-a-quarter inch invader is capable of spreading throughout the Norfolk Broads area and beyond.

And the NDAA chairman, Tony Gibbons, has declared war on another enemy alien that has the clear capacity to harm the Broads' thriving fish stocks.

'Obviously, we have to continue using keep nets in competitions but, in these cases, we are begging match anglers to dry out their keep nets completely after use because this damaging creature and its eggs can survive out of water in a damp net for days until it is dropped into the water elsewhere,'explained Gibbons.

'I emphasise this is a request to our members and permit-holders for the new season. We do not intend to try and enforce this, but hope common sense will prevail to demonstrate anglers are doing their bit to control this pest.'

NDAA waters involved are the River Bure, St Benet's Abbey and Woodbastwick, the River Thurne at Cold Harbour and the Ranworth and Woodbastwick Decoy Broads.

Now to the most important aspect of the new season – prospects.

The adjectives we are searching for range from promising to superb, depending on the chosen venues.

EA surveys on the tidal River Yare indicate there are massive shoals of bream and roach, with one concentration of slabs located between the two entrances to Rockland Broad amounting to thousands.

In addition, carp specialists are seriously challenged by monsters running up to 40lb lurking in the reedy bays.

It is this potential for fantastic fishing that has swelled the attendance for the Saturday series on Norfolk's biggest river to a sell-out.

The River Thurne is chock-a-block with bream and roach right now with the surveys showing a biomass stronger than the nearby River Bure that carries a much heavier volume of water from its upper reaches while supporting quality shoals of coarse fish that will become apparent in the NDAA tournaments.

The little River Ant, which runs from Wayford Bridge, near Stalham, through Barton Broad and on to its confluence with the River Bure above St Benet's Abbey, now offers free bank fishing upstream of Ludham Bridge.

This was the happy stamping ground for local angling clubs in the early post-war years when thousands of skimmer bream and small roach were weighed in as far upstream as How Hill and Irstead.

On the main Broads, Hickling is beckoning those anglers who are not still choking on huge slices of humble pie, baked on the unforgiving fires of inaccuracy blaming the Broads Authority for the spring outbreak of Prymnesium in Catfield Dyke.

In the end, it was decided the relatively small death toll of mainly spawning perch was due to Hypoxia (lack of dissolved oxygen) and toxin due to the breakdown of the Prymnesium cells during a dramatic plunge in water temperatures.

Hickling and Horsey Mere remain Meccas of upper Thurne fishing for bream, roach and perch with fishing dinghies available from the Whispering Reeds boatyard at Hickling.

On the Norwich waters at Ranworth and Decoy loads of fish were seen actively priming on the breezy surfaces this week and members may book dinghies at �5 per day.

The Trinity group of Broads at Ormesby, Rollesby and Filby are special in that they remain completely landlocked for exclusive, top-quality fishing.

Opening week is traditionally for pike anglers spinning, some catching up to 20 fish in a weekend working their favourite lures from dinghies on hire at the Filby Restaurant (01493 368142) or the Eel's Foot (01493 730432).

In addition to the numerous pike, bream and tench into double figures are not uncommon.

The River Wensum is noted for brilliant tidal water bream and roach fishing in the heart of Norwich and massive carp lurk in the precincts below Carrow Bridge.

However, in recent years, the Wensum has become more famous for its catches of alien chub and barbel.

According to Simon Wrigglesworth, the Anglian Water bailiff at Taverham Mill, river conditions are ideal with ample weed cover for a brilliant opening weekend.

This forecast is also accurate for the day ticket stretch at Lenwade Bridge, the scene of excellent chub catches in the Wensum Valley Festival last March.

The less famous non-tidal River Yare also beckons chub anglers with stunning specimens in the Trowse mill pool.

In the upper River Bure, giant chub swim in the river between the trees and shrubbery decorating the banks between Buxton Mill and Coltishall road bridge, with the chance of a quality barbell from Oxnead.

• On the big fish circuit, a superb tench scaling 13lb 14oz was heaved out of an undisclosed Norfolk gravel pit by Norwich angler Lee Searle.

Also from the Bawburgh complex, another Norfolk tench specialist, Darryn Stolworthy bagged a brace of Tincas of 11lb 1oz and 10lb 6oz.

Carp of the week was a monster mirror of 33lb heaved out of Billingford fishery by permit-holder Paul Cushion, who added a 24lb common.

At Taswood, carp in the 20s fell to Geoff Greenaway, of Hempnall, Tom Normanton, Great Melton, and Julian Miller, Norwich.