Crayfish problems

Its no secret that Galloway’s largest loch, Loch Ken, is overrun with the much despised American signal crayfish (Pacifastacus leniusculus). These transatlantic invaders were (mostly) accidentally introduced into British waterways by fish farming entrepreneurs in the 70’s and now rank alongside Grey Squirrels and Japanese Knotweed as the most reviled of non-native species – higher if you are a fisherman. They have also been recorded in a tributary of the Skyreburn since around 1990. It is unlikely to be coincidence that there has been aquaculture near the loci of both outbreaks.

North American signal crayfish

There are four reasons why American signal crayfish are considered a problem:

  1. They out-compete our smaller delicate native white-clawed crayfish (Austropotamobius pallipes) as well as decimating their populations by spreading a fungal infection ( Aphanomyces astaci ) to which the American invaders are resistant. White-clawed crayfish have not been recorded in Galloway and are not native to Scotland, having only recently been introduced in a few protected sites in the far North.
  2. They outcompete fish for habitat, natural food and bait and can eat unhatched fish eggs, playing havoc with ecosystems – and earning the wrath of the fishing lobby.
  3. They have a tendency to burrow into bankings which can have a detrimental effect on lochs and river systems.
  4. They can survive out of water for several days and even travel for several hundred metres on dry land, so they can move into new waterways given half a chance – such as being caught and carelessly disposed of.

For these reasons, there are serious restrictions on catching them. Firstly, you need a permit from the Environment Agency (and written permission from the landowner). Unless you have serious research purposes (preferably aimed at exterminating them), this is highly unlikely to be granted. The banks of Loch Ken are littered with ugly signs threatening all manner of punishment to anyone caught trapping them deliberately. Should you inadvertently pull any up on a fishing line, you are obliged to kill them on the spot and dispose of them responsibly (remembering that dead females may still be carrying eggs). I would suggest doing this on a barbecue as they are delicious.

Which brings me to my gripe…could you feel it coming? I understand that a lot of people (including me) enjoy their fishing, and that this can have benefits for the local economy. I also understand that the fishing lobby is powerful round these parts and I will probably be vilified for dissenting from their zero-tolerance line, but does this really mean that we all need to be treated as idiots who can’t act responsibly? Surely if there are too many crayfish in the Ken (and moving into the Dee), people should be encouraged to reduce their population by responsibly catching and eating them?

A major creel trapping (counting and killing) project operated by Dee Fish in 2010 (under contract to researchers trying to get a handle on the scale of the problem) is the only recent impediment to their spiralling population. 700 000 or so were reported to have been killed, which seems to have barely dented the problem and there is an argument that it  may make things worse in the long run. Perhaps a more enlightened approach to managing the harvesting of the crayfish would be more helpful. If properly overseen, this could be at least a partial check on the population and allow for ongoing monitoring and a better understanding of the problem. And we might get some delicious free food out of it too…

In the mean time, as I understand it, legally there is nothing to stop you fishing them out by hand (or even with a shrimp net) and having a nice barbecue by the loch side. Just be sure not to spread them to new waterways….

Learn More…


  • ron collison says:

    certainly seems like a great idea to me. in the meantime , however, am concerned that i may get in trouble for accidently catching crayfish whilst fishing for trout. perhaps you could suggest which fishing methods should be avoided at all costs!!!!


    • mark says:

      If you have a permit, you can hardly be blamed for pulling up crayfish. If you do, you are required to kill them. Most of the trout aren’t there naturally either and I know which I would rather take home for the pot! It’s a bit like gardeners planting mint and then getting up tight when japanese knotweed out-competes it. We interfere with ecosystems constantly, and I would personally prefer to make the best of our mistakes. Incidentally, I am working on a recipe that includes crayfish, knotweed, ground elder and honey fungus. Possibly to be served with mares tail tea…

  • Jools Cox says:

    I have heard, fro a fisherman, that the trout in Loch Ken are getting bigger due to the inclusion of crayfish to their diet. The otters are doing well too! The regulations regarding catching and eating crayfish are being relaxed in England so bring it on, crayfish cruises on the Ken with a big pot boiling on board – crayfish, brown brad and butter and bubbly mmm!!

    • mark says:

      That’s really interesting Jools. First positive report that I have heard from a fisherman. I have been hearing lots of the opposite actually: economic doom and gloom from businesses depending on fishermen; 2 otters killed by irresponsible and inappropriate traps; rangers etc desperate to prosecute someone for trapping – the list of woe goes on.

      One complaint i’ve heard from businesses that actually own shoreside property is that even they can’t obtain a licence to trap. They are doubly irked as they feel no attention is payed to boats, floats, anchors etc removed from the loch to other waters that are likely to be carrying eggs.
      It seems to me like an ill thought out, narrow, knee-jerk way of addressing the problem, but I would be delighted to hear the thoughts of someone with a different perspective.
      If it won’t go away though, I am sure ‘family crayfish bbq’s’ could be a huge draw to the area.


  • Lucy Wallace says:

    Not my research patch, but I’ve seen enough otter spraint around Loch Ken to be convinced that the crayfish are now a major part of their diet. In all the scat I’ve looked at crayfish is the main constituent part. This may be because their natural prey is less available. I don’t know enough about the Loch Ken otters to say whether they seem to be benefitting, but crustaceans form a major part of coastal otter foraging strategies.

  • Oliver Brown says:

    Here in Australia, our fish are native and our trout are introduced. Yesterday I went to mate’s farm dam to fish stocked trout but it seems fished out – but in their absence, the crayfish catch seemed better. The trout (rainbows rather than your browns) definitely grow fat on them.

    • mark says:

      Thanks Oliver, thats interesting. As usual, a complicated picture. Nature is complex enough, but introduced species add a whole new layer!

  • sam says:

    I go to Loch Ken solely for the purpose of crayfishing – they are tasty as anything and I’m doing my bit for the local environment.

    Small traps and regular checks are the way to do it safely. Pop open a couple beers, pitch a tent and bbq the night away!

    • Aaron says:

      Hi Sam, i would love to have a go, where do i get permission from buddy ?

    • harvey gooding hill says:

      hi sam im thinking of doing he exact same thing but im only 16 and unsure of the laws in 2021 and i just found this forum and was planning on using traps that have a mouth of 9cm so that otters are unable to get into my trap

  • Richard Rowe says:

    will cray fish kill shinners in a fish trap??

  • John Holland says:

    I live by a river in the south which is said (like pretty much all rivers in the south) to be full of signal crayfish, although I’ve never met anyone else who’s tried to catch them. But my inability to actually catch any is driving me nuts, and if I read any more descriptions of easy, bountiful catches I’ll scream.
    I use a decent, otter-friendly crayfish trap, usually using offal as bait, occasionally cat food, and I’ve tried in many different places along the river leaving it overnight. I’ve never caught a thing except an eel. Either I’m doing something radically wrong, or this is the only river in the south-east that’s free of crayfish.
    Any advice? Perhaps, like Jesus’s disciples, I should throw my net over the other side….

  • David says:

    I know this thread is pretty old now, but although I’d heard of the loch ken crayfish issue, I hadn’t paid much heed until now.
    How are things progressing now in 2017, has anyone come up with a solution to allow the population to be managed.

    • Mario Boni says:

      No solution as yet 2023 but they are now through the entire loch , dead baits for pike is pointless unless fished under a float , well off the bottom

  • Philip Gibbons says:

    Crayfish live only in clean water – if there aren’t any then maybe the stream is polluted.
    I catch them with an old bicycle wheel covered with fine chicken wire, baler twine handle and a kipper matured in a warm place until offensive. If you catch a lot then you need volunteers to shuck them as it wears out the fingers. Of course, NEVER eat one that was not clearly alive when boiled. Wonderful with beurre blanc – bon appetit!
    IMO the legal stuff is outdated now, the invasion being complete in most places. The antis are usually the kind of people who won’t eat anything that doesn’t come in plastic.

  • ian says:

    long time ago now and used for shrimping but i have heard it works for cray as well, much like philip a kid with a mate we would get an old bike rim, mate worked after school for a grocer and got an old onion sack, large mesh orange coloured thing cut that and spread it out tied it across the rim to sag like a shallow net, tied string 3 legs at equal points round the rim all joined to a single string used to raise/lower it into the water,
    lastly tied a string directly across the rim to which a piece of fish was tied in the centre (got the fish bits for nothing from the local fishermen where they gutted their catch well it was us or the gulls :-)) we would lower off a jetty (seemed a popular haunt for shrimp) below the surface but where we could still see it and watch the shrimp crowd in for the food, you had to raise it very slow, too quick and they were gone in an instant as we discovered,
    once the rim broke surface you had em, one thing you had to do was avoid throwing a shadow on the water or as little as possible as that would put them off, easily transported on our pushbikes. you could use a cane/dowel as a rod to keep it away from obstructions. better than the tasteless crap from supermarkets.
    should be disinfected if not used in the same waters to avoid transfering anything from one place to another when used in fresh water.

  • Aaron Beattie says:

    2021 hi guys, it seems to be totally unclear to wether we can, catch, clean, cook these RSCrayfish at the bankside without ending up on the wrong side of the law, the population of these invaders is beyond enormous, stats recon that if every fisherman in the uk, let alone Scotland were to trap these invaders for food every single day, that in 20 years we might be on an even keil with them, everywhere on the planet is trying to kurb and try some kind of control on them, but Scotland has a no kill policy on them, maybe this is why the fish numbers have been declining in the last decade, all i want to know is can we go to Loch Ken and the likes, trap our RSCrayfish, boil them, bbq them and eat them by the waterside, thanks guys, Stay Safe

    • mm mm says:

      I agree – the information being shared isn’t great. My understanding is that you can eat them if you do it in situ – ie. don’t take them from the shore at which they are landed.

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