The Signal Crayfish Special

In the UK the signal crayfish is an invasive species, introduced from America in the 1960’s to be bred for food, as they are considerably bigger than our native white-clawed species. They were introduced into more than 20 countries and since then have spread around most of Europe’s in-land water systems.

In the UK they are thought to be in more than 80% of all rivers, streams, and lakes and have massacred our native white-claws. Apart from being bigger and competing for the same food source, signals also carry a fungal disease that travels as spores through the water that is fatal to our native species. If both the signals and white claws are in the same body of water but never meet, the white claws will still die.

For this reason along with the damage they do to other water life and the banks surrounding them, they should be caught in the largest amounts possible and disposed of, preferably with some butter and perhaps a touch of lemon juice.

Here are a few commonly asked questions when it comes to signal crayfish and how to increase your chances of catching some:

What is a signal crayfish?

The Pacifastacus leniusculus, more commonly known as the signal crayfish is a freshwater invertebrate, simply meaning it has a hard shell on the outside and lives in freshwater. They look like small lobsters and feed off fish, both live and dead, along with plants, fish eggs, and each other if the natural food supply starts running out.

They can grow up to 15cm long and often live in swarms, which makes them easier to catch but also causes huge amounts of damage to the water system. They like to burrow into the banks of where they live during the colder months and when they do this in the hundreds it causes the banks to collapse a foot or so the next spring when the rains start. Over the years this can create big problems when the banks are at the end of people’s gardens or close to a workplace, but because of how quickly they breed it is very difficult to completely remove them from a water system.

Is it legal to catch crayfish in the UK?

Not only is it legal, but it doesn’t cost anything to get a license to do so. In the UK the first thing to do is buy your traps, most crayfish trap sellers will only stock UK legal traps, which means they will be a certain length and have specific-sized openings. After you have your traps you need to apply for a license from the EA (environmental agency) who will require information on where you intend to use your traps and also photos of them.

As long as you don’t intend to use them in an area where there’s known to be the protected white-claw species or some other protected animal, they will grant you a license and plastic tags to put on your traps to show they’ve been approved.

The whole process is free as it seems the EA is just happy to have some of the invasive species removed from local waterways. Another good thing about catching crayfish is there are no limits on what you can take, as there are with certain fish and shellfish in particular areas. You can literally walk away from a river with several buckets worth, and it won’t cost you a penny and no one can legally stop you. The only other factor about trapping crayfish legally is that you’ll need permission from whoever owns the body of water you intend to trap in.

When is the best time to catch crayfish?

Traps should be set at dusk or mid-afternoon and left until the next morning. Crayfish are most active at night and normally take a while to smell the bait and walk over, so don’t expect to leave your trap in for 20 minutes to see it packed full.

The other thing is that they don’t like it when it’s too cold. They don’t hibernate over winter but they do go to sleep in burrows as deep as 2 meters dug into the banks if it’s cold enough, so you won’t be able to work them out of a burrow even if you find one.

If the water is below 10°C they will go for a nap and not come out until the water warms up again. These naps can last for several days or even weeks if the water remains cold enough, so make sure you go out on a warm day.

In summer you’re fine for the whole season, but in winter you have to get lucky enough for a warmer day. If it suddenly warms up for a couple of days mid-winter, then get the traps out as they will come out for a food boost before going back to sleep.

How do I catch Signal crayfish?

You can make your own trap but it might not get approved by the EA, but they are normally quite cheap and will probably cost less than buying all the materials anyway. My own traps are the extendable tube kind pictured below, and three of them cost me just over £20, so don’t worry about the hobby being expensive.

As for bait, the single best thing to use is fresh fish, preferably salmon or trout. The favorite food of signal crayfish is fresh fish, and they are more likely to recognize the smell of something they’ve eaten before than saltwater fish they’ve never tasted.

The fish should also be fresh as even though they do eat decomposing meat, they much prefer it fresh. After freshwater fish other baits that work well include bacon, those cheap hot dog sausages in the tin, and crab meat, just make sure it isn’t flavored with anything.

As long as the smells, they will come into the trap to find it, which means that you can use leftover pieces such as the head or the bones, just make sure it’s raw when it goes in the trap.

How to purge crayfish?

After you get back home with your bucket of weird little lobster-type things, it’s time to either cook or purge them. Since they sometimes eat decomposing meat and live in bodies of water less than drinkable, it’s a good idea to flush out their systems.

The best way to do this is with salt water, but make sure not to leave them in too long or they will die, and you should never EVER cook and eat dead crayfish. Signal crayfish will drown if they don’t make contact with air for between 3 and 6 hours, so make sure you put them in your sink as soon as you get back home. To purge them fill the sink with enough water so they are about half covered, then sprinkle some salt over them.

The saltwater will cause them to constantly poop out anything in their systems until they are empty. Since salt water kills them, it’s a good idea to leave them in there for no more than 1 minute, then wash out all the salt water with some fresh and do it over again. It should take no more than 2 or 3 water changes before they are clean, which you can tell from how much mess there is in the water. Since this process will kill them if it goes on for too long, this should be done right before cooking them. If you don’t want to eat them as soon as you get home, purge and cook them anyway and de-shell the meat to be put in the fridge or freezer for later.

How to cook Crayfish?

They should be boiled whole and only take about 4 or 5 minutes. The shells will change to red as soon as they hit the water, but they need at least 3 minutes to be safe, but no longer than 5 as the meat will start to toughen up.

One of the best crayfish recipes out there is the good old American crayfish boil. Simply boil a load of corn cobs with some potatoes and chopped-up sausage, and then when they are ready throw in your crayfish and serve as soon as they are done. Drain the pot and tip the whole lot out into a pile in the middle of the table, drizzle over some butter sauce and lemon juice, and tuck in.