I'm not sure you can. Such intruders are known to move across oceans even without human intensions. Depending on their life history, they may arrive in ships' fouling, ships' ballast water, or even attached to free floating logs and other marine trash. MB-Y

I think that a powerfull way to prevent invasions by signal crayfish is to take legislative action against the desires of some individuals to introduce this species: introduction ban, prohibition of use in aquaculture, and perpetual prohibition of comercial and recreational fishing of introduced crayfish. If they can not take any advantage of introducing this species, and they KNOW they will NEVER be able to get, I think that the probability of introduction decreases.

Best wishes.

Well, first step is to have a consistent law regarding to invasive species. In Spain there is not this law, and Signal Crayfish is a species susceptible to fishing, regulated and controlled as other fishing species. Of course, Signal Crayfish is very abundant in some places and native crayfish is nowadays a relict species...

Going past legislative control, (that currently appears to be failing in Scotland to some extent) rapid and early detection methods will be required. Some potentially exciting uses of environmental genomics may be the best means of rapid detection, either through routine catchment/ aquatic import checks, or by rapid response and confirmation/rejection of reports (I am not sure of the detail of these methods, nor how sensitive they are!).

It is a miracle that Ireland remains unaffected and more effort should be devoted to understanding why this is and how it can be sustained into the future.

In the SE Mediterranean, we can see how within the last 60 years about half of the commercial trawl fishes have been replaced by several invaders from the Red Sea. I was fishing in the Med. back in the 1950s when we first discovered a few fingerlings of the Red Sea species of lizard fish Saurida undosquamis. Within a year or so they became an important share of our catches. See my paper in the U.S. Fisheries Bulletin: The Invasion of the Red Sea Lizard fish,...etc. I don't thnk that any legal or commercial procedures can stop an invading species wherever they find a favourable habitat. This goes also for the Chinese carps in the US rivers, and for umpteen other species, once they can find a way how to cross intermediate areas. MB-Y

Thanks everyone for interesting suggestions. Menakhem, in this case the crayfish is freshwater and cannot cross the sizable seas to ireland unaided (but chinese mitten crab can). Antonio and Rafael, I agree with you that strict legislation is needed. The trouble is that the strictest legislation is in Ireland, with that in Scotland nearly as strict, but the English and Welsh legislation is different and full of loopholes. However, not everyone in UK realizes that the laws are different, indeed, some may not realize that there is a problem with introducing signal crayfish into Northern Ireland! I agree with Rupert that it is a miracle that Signals are not yet in ireland - it is how to sustain this miracle! Julian

The problem with freshwater species is that they can cross seas and oceans in ships' ballast water, wherever harbours are located in river estuaries, and as eggs in birds' poo. Like in everything, legislation is important, but it's never waterprooof. MB-Y

Raising awareness and continued work into eradication or control in Britain will hopefully cause a steady reduction in risk of further spread to Ireland. Presumably we know what the most likely routes of dissemination are between Britain and Ireland? Where the major shipping routes are, which trades that use those routes are likely to come into contact with signal crayfish, and the relationship between how frequently those companies make the journey compared to how frequently biosecurity checks are made?

Julian, maybe a possibility is to "press" over English and Welsh administration, showing the terrible threat and the legal position of nearby administrations. Perhaps you can obtain the support of scientific societies or administrations. I know that it is not easy, but I believe that it is necessary and you should try it.

Thanks for all your helpful replies. In Europe, and within Britain, the major routes of dissemination of Signal crayfish is by man - hoping to establish new populations for subsequent harvest, and ignoring the ecological damage caused by such translocations. The costs of these alien invasions have been estimated for Scotland, and far exceed the benefits, but when private individuals are concerned, these arguments fall on deaf ears. Crustacean experts are concerned but can do little, and the Northern Ireland and Republic of Ireland authorities have been notified but I think mount few biosecurity checks. The British (English and Welsh) authorities have their hands full with the problem. I think widespread public education may be one of the answers. Julian

Dear Julian,

I understand very well your concerns : in France, as you know, we have the same problem with non native crayfish. Now we have people who want to make money with species as the red swamp crayfish...The main difficulty with legislative tools is that you need money and people to enforce them which is rarely the case considering all the water bodies in a country. In Scotland, is the native crayfish recognized as a flagship species? If so, it may be worthwhile to establish a communication strategy? It could help people to become aware about this problem... It would be a good start. But I am sure you have already think about it... By the way, I would be very interested by the evaluation of the costs/benefits you mentionned.

Nicolas

Early day motion 659 CONTROL OF INVASIVE FRESHWATER CRAYFISH

http://www.parliament.uk/edm/2013-14/659

Signal crayfish are amphibious. The live transport and sale of all alien crayfish species should be banned immediately.

I believe you need a combination of several measures since one on its own is bound to fail. The combination would inlcude legislation, biosecurity, education and all with some sort of value proposition (which could include cost/benefit - not just economic though). A community based action research (eg. "crayfish watch") would be great to get broader community involvement. The benefit of such an approach is that it could apply to other potential invaders.

Thanks everyone. Anthony, the Early Day motion to the UK Parliament shows the concern felt by some parliamentarians, and the high costs involved in signals invasion. Research in Yorkshire (England) by Stephanie Peay (KMAE 2009, 394-395) showed the negative impact of signals on salmonids. Salmon and trout are economically very important for Ireland and Scotland, but Scotland has no indigenous crayfish. I believe the economic analysis there, requested by Nicolas, is not yet published. Finally, Satish is recommending a promising multi-pronged approach, based around community action.

Dear Julian,

Please find my suggestions:

1) Strict ban. The U.S. Fish and Wildlife Service has declared the members of claridae (catfishes) as "injurious wildlife" and their import is banned. Similarly Germany banned the trade of C. gariepinus. This can be also applied to PFL both in N. Ireland & the Republic of Ireland.

2) Have a constant eye on regular and internet-based aquarium trade (for illegal by-passing)

2) Public education: scientists & citizen-scientist networking

3) Early detection and contingency plan

4) Strict protection of the most important APP populations (probably restricted or even no-go areas for public)

5) Live bank for different APP populations

6) Prey to the crayfish god...

Unfortunately In Grecce it has escaped from an artificial lake and now it is spreading to the nearby river...

My best,

Costas

Dear Julian,

it may not answer your question but here is a recent issue from a meeting about invasive crayfish in France http://www.onema.fr/IMG/EV/meetings/Ecrevisses-UK.pdf

Best whishes

Nicolas

Merci bien Nicolas. An interesting summary and information clearly presented. Julian

It is just possible that it already is marketed in Ireland in specialist fish shops as it is elsewhere in continental Europe. Specimens may then become released to the wild in the same way as the American lobster in European waters. Incidentally Cherax spp have been seen in aquarium suppliers and following a warm summer, as it was this year, it could survive in the wild in shallow bays and has anyone looked at what parasites it might transmit?

Thanks Yibekal and Dan for your interesting contributions to this difficult problem. Native crayfish are now protected in ireland and in Europe, so trade is not permitted. This makes it difficult to modify relative pricing of the native and invasive species. There are arguments for allowing exploitation of natives, to increase their perceived value, while otherwise protecting them - Salmon are a case in point. No non-native crayfish may be brought into Ireland, but we usually don't hear about any illegally bought and sold. However, several European countries have different trading rules and their lists have up to 30 crayfish species - this could be the source of alien invasive species. I believe that public education in the laws protecting native species, and the reasons for them, remains of paramount importance.

Hi Julian, For certain I have seen Cherax in aquarium shops, termed 'blue lobsters'. Possibly C. quadricarinatus, I did not have your account at the time that you published with Pierre David and Catherine at the time. I have - in the past - seen crayfish, not our species on sale in Dublin at fishmongers. I did not think it was the species already present in Ireland. In any case the evidence would suggest that the species, termed native, may in fact be an introduction from an earlier time as you know. Bit of an oxymoran! So how to term its status: a naturalised an alien, a cryptogen but surely not native. There are other cases in Europe of species that have been presumed to have been native that have protection but are probably introduced. In any case I am comfortable with preserving 'our' crayfish as it is an outpost for the species.

To get back to the original question the sale of all crayfish should be banned as you suggest and the tough bit, enforced. I think this would help. I do not know of diseases the Australasian crayfish should these be released to the wild. Being a tropical species it may be of note that many Shannon embayments attained 23C this summer and in Kilglass Lake 28C, so I would think they could survive in these situations althoughbeit for a short time.

Thanks Dan for helpful comments. There is some data about diseases of Cherax in 'Atlas of Crayfish in Europe'; they are highly susceptible to plague, which has been used to eradicate them, and they host a Psorospermium. The tropical Redclaw is affected by a Rickettsia-like organism. Yabbies are warm temperate; stocks have been naturalised in parts of Europe so their potential for further establishment is high .

Costas has a good outline. However, as long as people want exotic animals for pets or food and are able to move them across borders illegally, this problem will persist. Humans always find a way to skirt the regulations!

Joy's reply is unfortunately accurate. The predicted invasion hasn't yet hit Ireland, and a combination of helpful suggestions by Costas and others, if worked out and implemented by our wildlife personnel, particularly the education of public and managers, could help prevent that happening. The evidence from Great Britain indicates that containment, or trapping to 'eat to beat', doesn't work.

Humans are homogenizing the earth's flora and fauna.

Well Ireland being an island tends to receive species that have previously become established in Britain. This is the overall trend; but it could change with the level of trade between Ireland and Europe. Already several species have become established in Ireland which heretofore were unknown and all will have appeared in Britain before being recognised in Ireland. However, we can seldom prove this. Already within the last two decades Ireland has Dreissena, Corbula, Hemimysis, Craspedacusta, Chelicorophium and others revealed. So whatever arrives in Britain, and based on past evidence, is likely to arrive in Ireland. So perhaps if we have a better understanding of the routes that such species may be spread then we can have better controls - if the state is willing. Currently we do not have a good knowledge of pathways and their vectors for many species and we need to appoint levels of certainty to any transmission and further we need to know much more about natural spreading processes. This area of research is not adequately funded. If natural processes are efficient as in the case of Anguillicoloides, then management actions are more likely to fail.

So what are the likely vectors for the species you are concerned about Julian and can we apply some level of certainty to these as to how they have already spread elsewhere. Then perhaps we might convince managers to respond appropriately.

Thanks Dan for summarising the irish situation with alien invasive invertebrates. Across Europe the overwhelming vector for all invasive crayfish is humans, who ignore (or are ignorant of) legal regulations and work in two main ways; (1) they may transplant crayfish to new locations, with the hope of establishing a new fishery, and/or (2) buy crayfish off the web for home aquaria, and then dump surplus unwanted crayfish into the nearest pond or stream. The first is documented across Britain and Sweden, and the second, across Europe, particularly Germany and adjacent countries. I believe we can only prevent these happening in Ireland if regulations are clearly publicised and enforced by the appropriate managers, backed by a public education blitz.

Unfortunately these problems seem universal.  I wanted some crayfish for a teaching exercise some years back and had no difficulty purchasing a bucket of rusty crayfish sold as bait to bass anglers.  We gained tench when an individual in Quebec was denied permits 2 or 3 years in a row and decided to build his tench farm anyway...and of course a storm blew out a dam and released them to the river draining Lake Champlain...so now we have tench.  Two or three years back we picked up alewife; more recently spiny waterfleas.  My benthic samples from Missisquoi Bay of Lake Champlain contain 85% European fauna by biomass (Valvatid snails; Bythinia; zebra mussels).  A ban on crayfish importation to Ireland seems essential; enforcement is not easy of course.

We can't

Hi Julian, I agree that humans are the main vectors. Given that Ireland is an island, thoeretically it should be easy to prevent alien species from arriving in the first place. However, in practice,  it is difficult given the multiple ways in which humans can introduce them, intentionally or otherwise. Appropriate  legislation, enforcement,  education and publicity may all be required in a multi - pronged approach.

Thank you everyone for contributing. This problem is ongoing, and this summer we have had a crayfish plague outbreak, the first in 30 years. The plague type is associated with signal crayfish, but so far, thankfully, no signal crayfish have been found, leading to the possibility that the oomycete was brought in accidentally. There is a good chance that the outbreak will burn itself out, with the loss of substantial regional stocks, but if signals are confirmed, the widespread Irish stocks of white-clawed crayfish are likely to follow those in UK, France, Spain, Italy etc. into near-extinction.