Tuesday, 7 August 2012

Is Crayfish on your menu?

I recently read a book where one person was described as being in the habit of catching and eating freshwater crayfish. However, it was the invasive American Signal Crayfish that was the species being caught and eaten. Not the protected white-claw crayfish.

American signal crayfish are threatening Yorkshire's native white-clawed crayfish populations because they have better resistance to parasites and are less fussy about what they eat.

You can do your bit catching and eating the American Signal crayfish. However, first of all  you need to get permission to go crayfishing from the Environment Agency. The Agency needs to ensure that no one accidentally traps and eats the white-clawed crayfish.

Read this to get some info from George Monbiot on what you can achieve. Not only that he includes information on building a crayfish trap.  Click Here

Yorkshire is one of the last strongholds of the white-clawed crayfish, which is being driven out of Britain's waterways by its hardier American cousin, introduced to Britain in the 1970s for fish farming. The advance of the signal crayfish over its native rival has implications for the biodiversity of Britain's rivers as the diversity of prey is reduced and the invaders' appetite for fish eggs causes a decline in the fish population.

Although the white-clawed crayfish is listed as an endangered species in Britain, the reasons for its decline and the American species' success have not been well understood. Now, researchers from the University of Leeds' Faculty of Biological Sciences have been trying to work out why the signal crayfish has been gaining the upper hand, and how this information might be used in conservation projects.
Their study, published in the online journal PLoS One, compares how quickly the two different species deal with food. The American signal crayfish ate up to 83 per cent more food per day than did their native cousins. 

The research also showed that white-clawed crayfish are much more choosy about what they eat, preferring particular types of prey, while the signals eat equal amounts of all prey. 

Dr Dunn said "The huge appetites of the signal crayfish can have a massive effect on the whole ecosystem. In particular it affects biodiversity because there is a reduction in the numbers of prey. In some Yorkshire rivers, for example, the fish population has declined because signal crayfish are eating large numbers of fish eggs."

Dr Dunn believes studying the effects of parasites on host species can offer vital clues about species conservation. "Parasites are a fascinating and vital part of any ecosystem and you have to consider their effects when looking at biological invasions," she says. "We hope our findings will help us make predictions about how this invader might spread and help with management strategies."

Humans too can play a part in protecting the white-clawed crayfish by understanding how invading species spread. The signal crayfish is able to move overland of its own accord, but may also be inadvertently moved around in, for example, damp fishing gear. "We need to be much more careful about how we move animals and plants around from habitat to habitat, and raise public awareness about these issues," says Dr Dunn. The research was funded by the Natural Environment Research Council, in partnership with the Environment Agency.


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