Rare native crayfish found dead in a Norfolk river are feared to have been killed by a fungus

August 13, 2009
Eastern Daily Press

Rare native crayfish found dead in a Norfolk river are feared to have been killed by a fungus.

Three threatened white-clawed crayfish were found in the River Thet at Thorpewood caravan site, between Thetford and Diss, last week.

The CEFAS (Centre for Environment, Fisheries & Aquaculture Science) lab is analysing the animals to see if they are infected with the highly virulent fungal disease Aphanomyces astaci, commonly known as crayfish plague.

Native crayfish were formerly widespread but the disease has already wiped out large populations in England and Wales.

They now exist in increasingly isolated populations in the upper reaches of rivers and the River Thet is one of the few that support a population.

Crayfish plague is carried by crayfish introduced from America, notably signal crayfish, which are not susceptible to the disease themselves.

Signals - the crayfish sometimes sold in restaurants - were introduced to consume sickly trout in fish farms.

The disease is spread by affected crayfish or, more commonly, equipment such as fishing nets, keep nets, footwear, boats and farm machinery being transferred from infected waters.

Environment Agency officials are urging anglers to ensure nets and gear are dried after each trip to avoid spreading the fungus.

Senior monitoring officer Nina Fielding said: gThis suspected outbreak is really worrying for the future of our native crayfish. There are only a small number of these endangered animals left in the Great Ouse catchment.

gWe urge all river users to clean and dry or disinfect any equipment before taking it from one river or lake to another.h

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