by Sam Carlisle

Sam Carlisle has a go at signal crayfish trapping, an essential conservation tool used to control numbers and help save our native species.

Photo credit: Simon Finlay

As far as destructive invasive species go, the signal crayfish doesn’t draw the same level of public ire that grey squirrels or muntjac seem to. While they may be less visible in the landscape, their effect is no less catastrophic, especially for Britain’s native white clawed crayfish.

Introduced by the government in the 1970s, there was hope that these North American imports could be farmed. The market for crayfish was buoyant, and our native stocks had been badly impacted by crayfish plague, a fungal disease whose spores are easily spread through water. What started as a hopeful solution quickly turned into a nightmare. The signal crayfish is adept at escaping, able to walk over land in search of new habitats. They have been recorded travelling more than 300 metres through fields in a single night, so it was no surprise that they soon found their way into waterways that neighboured the farms. From here they spread, much like the grey squirrel, into almost every corner of England. Relentlessly, they outcompeted the smaller native crayfish, diminishing their food supply and dominating their breeding sites. Worse, they turned out to be carriers of crayfish plague, which quickly wiped out the native population in many watersheds. Ever since, there has been a battle to eradicate the signal crayfish. While there is no easy solution, and realists sadly accept this is now mostly about containment rather than cure, trapping remains an essential conservation tool in the effort to save our native crayfish. The by-product is truly delectable shellfish that couldn’t be easier to prepare.

In the hope of a delicious meal, and to learn more about effectively trapping crayfish, I headed to the Raveningham Estate in the Norfolk Broads. They have historically had issues with signal crayfish eroding banks of ponds, caused by the underwater warrens they create for nesting and hibernation. They have also had success with trapping them. 

“A few years ago we’d catch buckets and buckets of them,” explains Adam, a keeper on the estate and key crayfish controller. “But recently they have reduced in number, thanks in part to trapping and also to a pair of otters who seem to have had a good impact.” Although signal crayfish seriously disrupt food webs by eating vast quantities of invertebrates, fish eggs and vegetation, at least they have a native, and clearly effective, predator in otters.

The first thing to know about trapping crayfish is that you’ll need a licence in order to do it legally.  These are relatively easily obtained from the Environment Agency website. As long as there isn’t a high risk of catching native crayfish, you should be granted one.

It is also vital to make sure that your trap is of legal dimensions, and especially that the opening the crayfish crawl through is no more than 95mm wide. There have been numerous examples of illegal traps, with openings that are too large, catching and killing otters. The final legal point to bear in mind is that you cannot release a signal crayfish once caught. Even if you catch one that is too small to eat, it should be killed and thrown away. Once the legalities are dealt with, trapping crayfish is relatively straightforward. During the winter they are normally inactive in their warrens, and while the odd one may be caught, it is far less productive. May through to September is the prime time.

Signal crayfish are opportunistic feeders and so will fall for more or less any bait. Adam was using an old chicken leg, but has had good success with tinned cat food as well. The essential step is to ensure you put something heavy in the main part of the trap so that it is anchored to the bottom of the pond or stream. The crayfish will be crawling along the river bed, so anything suspended in the middle of the water column will not work. In a river it is best to find a clear flowing section free from weed. In a pond, an area where the bank slowly slopes down is best. The baited trap should be securely fastened to the bank, using something like paracord, and ideally left overnight. If you are placing a number of traps then space them out rather than putting them all in the same area. When you return the next morning you hope that the trap will be heaving with these invasive delicacies!

If the Environment Agency have granted you a licence, you’re unlikely to catch one of the native white clawed crayfish. However, it is always best to check. The most reliable indicator is that the underside of a signal crayfish claw is red, whereas the native ones are an off-white colour.

Adam’s trap, set the night before, is moderately full. Not a feast, but enough for a decent meal, with one or two whoppers. “They’ve got pretty powerful claws which can give a fairly nasty nip,” Adam declares, as he delicately prizes one from the trap and places it in the bucket. To avoid a pinch, you’ll need to pick them up using your thumb and forefinger from just behind the base of their arms. 

Adam’s favourite way to cook them is immediately in boiling water for four to six minutes, depending on their size. Cooked straight from the river, there is no need to purge them. However, if you keep them alive for a few days before cooking, it is best to put them in some very salty water for five minutes, before rinsing again with fresh water. Once cooked, bending the tails backwards and twisting them off will leave you with a perfect mini lobster tail, and should keep any guts and the like in the head. Simply boiled crayfish tails are delicious on their own with something like a Hollandaise sauce or added to a salad. However, if you’ve been fortunate enough to have a real haul, there is nothing better than a classic Crawfish Broil shared amongst friends. This recipe from the Louisiana Gulf, involves boiling up spiced Andouille sausage, corn on the cob, potatoes and other delicacies in a spiced broth. Once the constituent parts are done, bundles of crayfish are added for the final minutes. This is typically poured onto an enormous platter and eaten with your hands. It is a wild, medieval-style feast: visceral and delicious.

 

This article was first published in the Summer 2021 issue of My Countryside magazine.

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