Sunday, 31 January 2010 17:14

Crayfish conundrum for angling


Carefully placed bait, a perfect cast; all to be ruined by a brazen crayfish sweep the bait from the line. More likely than not it is one of the North American crayfish that are rapidly spreading through our waterways. This species is affecting fisheries, rivers and lakes all over the country and has contributed to the devastating loss of British white-clawed crayfish which play an important role in healthy rivers.

White Clawed Crayfish How do signal crayfish affect fishing?
Although signal and native white-clawed crayfish are similar to look at there are significant differences between the two species.  North American signal crayfish grow larger, produce more offspring and are generally more aggressive.  Native white-clawed crayfish are a keystone species and an important part of the food chain in the clean, healthy rivers they are traditionally found in.  Signal crayfish can often lead to an imbalance in freshwater communities, over predating the aquatic invertebrates that many fish species feed on and even eating fish eggs.

Not only do signal crayfish affect fish stock directly, they can also have an impact on the quality of river and fishery banks and have even been known to cause severe damage to fishery dams.  How?  Both signal and white-clawed crayfish are burrowing species, however, signals create much deeper and more extensive burrows which cause banks to become unstable and can undercut dams. 

Trapping myth
As we become increasingly aware of the havoc that signal crayfish are causing, there has been an increase in programmes and articles recommending catching them for free food.  Read the fine print though – many people do not release it is illegal to trap for any species of crayfish without a trapping licence from the Environment Agency.  Casual trapping might seem an obvious way of reducing signal numbers, but this is not the case.  Large crayfish feed on smaller individuals, so casual trapping for food removes a natural predator. This may potentially result in a rapid growth in population.  Illegal crayfish trapping can unintentionally affect other wildlife, demonstrated recently by recorded cases of otters drowning in illegal crayfish traps.  Trapping for signals also greatly increases the risk of accidentally spreading a deadly disease that is wiping out native white-clawed crayfish.

Deadly disease
Most anglers’ are aware of the large number of waterway diseases that can affect fish stock and the importance of disinfecting equipment and boots appropriately.  The crayfish plague can easily be carried by fish or people and although harmless to either, it is lethal to white-clawed crayfish and can wipe out entire populations in a matter of weeks.  This fungus-like disease rarely affects signal crayfish, which can act as carriers.  It releases spores which travel through the water and attach onto anything they come in contact with.  A waterborne disease, the spores require moisture to survive so please wash off all you equipment and most importantly dry it out before changing your fishing location.  If you are able to disinfect equipment please do, if not make sure it has dried completely before use.

Stop the spread     
North American signal crayfish and the crayfish plague are wiping out native white-clawed crayfish populations and with up to 70% lost in the south west and no native crayfish left in some parts of the UK at all, if we don’t act now it will be too late to save this species from extinction in the UK.  Simple steps can save this species.  Do not trap for crayfish without first consulting the Environment Agency and obtaining a licence and never remove crayfish from a waterway or use any part for bait, these actions are illegal.  Do wash and dry all equipment and footwear after use and if possible disinfect appropriately.  Finally protect native crayfish habitat, which is also beneficial to other animals such as invertebrates and fish and report any sightings to your local Environment Agency office.

If you need advice on North American signal crayfish or crayfish legislation please contact your local environment agency, information can be found at:

North American Signal Crayfish

Save a species:
The South West Crayfish Project is a partnership of organisations working to prevent the continued loss of native white-clawed crayfish in the south west.  Operating the largest strategic translocation, or re-homing programme, of native crayfish in the UK to date they work closely with the local angling community. 

If you want to know more about the plight of the white-clawed crayfish and how the South West Crayfish Project is working to conserve the species through re-homing and breeding programmes and education please visit the websites below and search for ‘South West Crayfish Project’: or

Source: South West Crayfish Project

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