Signal Crayfish

[nurglespuss]

You have to be qualified in it. The best person to constact is Dr. Roy Wiles, he is one of the countries top experts.

 

[severum boy]

Havent White-claws got white on the underside of their claws and Signals have larger pincers?

 

[nurglespuss]

generally speaking yes.

The signal is much larger, generally darker, with charactersitic claws however, when viewed from above, cray fish of similar size (differing age) look similar enough to be fairly indestinguishable. And of course, once you remove a signal crayfish, you cannot knowingly put it back. There is then the problem (as was seen in thinitial picture) of cleaning/keeping the animals. You have to clean feed them, before they are fit for human consumption. Any water removed from the tanks must be specially treated before disposal, otherwise you will spread the fungal spores to your local water ways, killing more of the local white claws.

 

[raptorrex]

Siganl Crayfish are an introduced alien from America.

They bring a fungus ith them which is deadly to our native white claw cray fish.

Also, you need a license to remove ANY crayfish from British waters.

true though if you live in an area like the midlands you can get both trapping and keeping licenses with no problem.

Siganl Crayfish are an introduced alien from America.

They bring a fungus ith them which is deadly to our native white claw cray fish.

Also, you need a license to remove ANY crayfish from British waters.

No you dont. You can keep Signals anywhere that they have established large feral populations.
Quote from DEFRA website:

In addition to the 1981 Act, further legal controls on the keeping of non-native crayfish were introduced in 1996. The Prohibition of Keeping of Live Fish (Crayfish) Order 1996 was made under the Import of Live Fish (England and Wales) Act 1980 this legislation makes it an offence to keep any crayfish in England and Wales, except under licence, an exception being the keeping of signal crayfish in those parts of England where extensive populations existed before the Order was introduced and such stringent controls were deemed inappropriate.

Having a further look around the website shows that infact most of the UK is able to keep Signals.

whatever you do please return the large signals back to the river, but take as many of the smaller ones as you can. Signals are very cannibalistic, when mature. it has been reported time and time again. blind trapping often ends up with an increase in the Signal population.
as for needing to be a biologist to tell Signals from White claws. there is no rule that says that. you just need to take it on the chin if you get it wrong. i know many people who can ID a Cray at 20 paces, very few of them are even academic, never mind Biologists. lol its a bit like saying only a Baker can id what bread you are eating.

whatever you do contact DEFRA, and the land owner before you start trapping, in many areas it is simply a case of putting in a request.

Again please put the really big ones back, they do a much better job of keeping the population down than us

 

[Fighterfish]

We have the permission of the landoner (my friend). The crayfish we catch are signals and the population is going down. It may be the colder winter but last summer we caught about 25 each time we went for about 4 hours. So far are highest catch has been 12 in 5hours.
Also the river is a chalk stream truout river which the brown trout are beginning to repopulate due to the lesser amount of crayfish. Signals eat trout eggs. Also DEFRA encourage the removal of these signals as they decimate populations of native wildlife. The small ones to not create a larger problem as they are unable to breed.

 

[nurglespuss]

UMMMmmm BOBOBOY....

Its the law that you cannot replace signals when removed from the water....

 

[nurglespuss]

YOu do lnow signals can breed from the fourth instar? and that everywhere in britain the population is on the increase? If you really have noticed a demonstrable decline in the population of signals, and incease in that of the brown tout, I suggest you write to DEFRA/nearest University to tell them about it, as it has not happened anywhere else...

Alos a note on how signal populations spread. Signals are terratorial, and larger specimens hold the larger territories. populations will spread via clump/explosion throughout a water way, generally only halting at physical obstacles. Crayfsh will however leave the water to explore once the population increases.

In reference to the trout, the expanding trout population will trigger an expansion in the crayfsh population.

Hope that helps.

Check out these articles that ROy co-wrote

http/links.jstor.org/sici?sici=0888-8892...%3E2.0.CO%3B2-O
http/www.alr-journal.org/index.php?optio...051/alr:1996030

Also; It is illegal to introduce/re-introduce any signal Crayfish into British waters - So if you take it out, you have to take it with you.

 

[raptorrex]

UMMMmmm BOBOBOY....

Its the law that you cannot replace signals when removed from the water....

it is illegal to release none native Crayfish into a river system. however in this case yo are not introducing the Cray to the river simply returning it.

get real will you, if returning the larger Cray to the river, in anyway helps reduce the Signal population. common sense tell you to do it. a simple bit of research will reveal the truth of the Cannibalistic tendency's of the Signal.

I say it again, Please return the larger Signals to the river they came from! every little thing we can do to help the White claw needs to be done.

 

[nurglespuss]

I am sorry but you are wrong.

I worked for a year on signal crayfish, I know they are cannabalistic.

Think about what you are returning: the prime breeding stock, the males and females capable of producing the larger output of new crayfish.

My point is perfectly accurate, if you remove signals from british bater ways, you cannot introduce/reintroduce them, as they are NON-NATIVE, it does not matter that you pulled the non-native species from british waters.

Do not return them, and I am sorry, but you need to widen your research in this matter.

 

[OohFeeshy]

I think you're being a bit OTT. Legality doesn't matter- you're hardly going to have the British Crayfish Police standing over your shoulder making sure you don't put them back in. And RE 'the prime breeding stock', there's more than one aspect. By returning bigger crays and keeping the smaller ones, not only are you encouraging natural cannibalism, you are also returning the individuals with the shortest lifespan and destroying the next generation.

 

[nurglespuss]

I'm not being OTT, I merely value British wildlife. The white claws will more than probably be all but wiped out by the signal. Activities, such as amature fishing and replacement, only encourage this decline. Signals live for around 6 years, the larger ones are at the end of their life span, but are the most succesful breeders. The smaller sizes (instar 5- 3) are also edible/worth catching, but will not dent the population as you imagine. The real population is governed by unhatched eggs, berried females and instar 2 and below. These are the unseen popultion providers. Using population models, it is easy to see that the removal of adults has a good SHORT TERM effect on the population, and encourages predation of the younger generations. Removal of young from instar 5-3 also has a noticeable effect, and if it were possible to remove a significant number of them (which it is not) would eventually reduce the population to its minimum (via super predation). However, the greatest effect is achieved by removing the very youngest generations, and targetting berried females, this however is virtually impossible as you can imagine. The net result is that removal of many many signals is excellent, from all geberations is even better, and will have the greatest cumulative effect hand fishing can achieve. Replacing the adults does not cause enough losses of younger crayfish to warrant their replacement. This is something that everyone should take very seriously, especially as it is us as hobbyists that have helped perpetuate their spread (along with various amphibians and plants) along with commercial ventures. Take it seriously, read the research (I provided some examples further up these posts).

Thank you.

 

[raptorrex]

I'm not being OTT, I merely value British wildlife. The white claws will more than probably be all but wiped out by the signal. Activities, such as amature fishing and replacement, only encourage this decline. Signals live for around 6 years, the larger ones are at the end of their life span, but are the most succesful breeders. The smaller sizes (instar 5- 3) are also edible/worth catching, but will not dent the population as you imagine. The real population is governed by unhatched eggs, berried females and instar 2 and below. These are the unseen popultion providers. Using population models, it is easy to see that the removal of adults has a good SHORT TERM effect on the population, and encourages predation of the younger generations. Removal of young from instar 5-3 also has a noticeable effect, and if it were possible to remove a significant number of them (which it is not) would eventually reduce the population to its minimum (via super predation). However, the greatest effect is achieved by removing the very youngest generations, and targetting berried females, this however is virtually impossible as you can imagine. The net result is that removal of many many signals is excellent, from all geberations is even better, and will have the greatest cumulative effect hand fishing can achieve. Replacing the adults does not cause enough losses of younger crayfish to warrant their replacement. This is something that everyone should take very seriously, especially as it is us as hobbyists that have helped perpetuate their spread (along with various amphibians and plants) along with commercial ventures. Take it seriously, read the research (I provided some examples further up these posts).

Thank you.

If you really valued British wild life, you would support the return of the larger Cray. Perhaps its just your lack of understanding, or is it just blind compliance with, what you see, as the letter of the law.

It is proven that the larger mature Cray are cannibalistic, something you admit yourself, it not too hard to see that removing them will help increase the overall population. and despite you claim that removing these adults "Replacing the adults does not cause enough losses of younger crayfish to warrant their replacement". the evidence points, if not proves, you are wrong. It is well documented that heavy trapping, has lead to an increase in the population, when the next survey is taken.

If an adult Cray only eats two smaller ones, removing it will simply remove one cray, but allow two more to live. HUMM even that is an increase in the population simply by removing one. not very bright you would agree.

the solution is of course to use smaller traps, then you will not have to return any Cray. However the fact remains that returning larger Cray to the river, will help not hinder the reduction of the Signal population.

 

[nurglespuss]

Hi, you see this is what happens when you state your opinion rather than actually looking at the facts.

Let me put it very simply, and as I am qualified, very accuratly:

Replace one large cray fish, it may concsume 'x' number of smaller crayfish.

It may also migrate, spreading the population, it will also breed with females (if male) increasing the number of signals to far greater levels than those it removes via consumption. Replacing berried females is extreemly irrisponsible - an adult female can carry 4000+ eggs.

Removal of adult signal: you have removed 'one' signal, you have also removed every potential signal that could have resulted from it breeding, you have also helped reduce the risk of further population spread.

Weigh up those facts please.

Oh and you have indigestion yet?

Now, unless you can find some actual peer reviewed/research based evidence supporting your theory, then please don't spout unproven, illegal and damaging ideas.

 

[OohFeeshy]

If you only take out larger crays, you leave the smaller ones. The smaller ones can then breed to their hearts content until they're big enough for you to consider taking out. The bigger ones can still breed, yes, but they have a much shorter lifespan, and there's no guarentees you're going to catch the smaller ones when they've grown up. Removing *any* signal is beneficial whether it's big, small, male, female, whatever. Plus, the egg stage is when they're most vunerable- out of thousands of eggs, only a few will survive to adulthood.

Edit- You mentioned migration- it's probably more likely for smaller ones to migrate. Large crays are large because they found a nice territory with plenty of food and have chased off or eaten any rivals. Young crays are still in competition and are more likely to wander looking for territory.

 

[raptorrex]

Hi, you see this is what happens when you state your opinion rather than actually looking at the facts.

Let me put it very simply, and as I am qualified, very accuratly:

Replace one large cray fish, it may concsume 'x' number of smaller crayfish.

It may also migrate, spreading the population, it will also breed with females (if male) increasing the number of signals to far greater levels than those it removes via consumption. Replacing berried females is extreemly irrisponsible - an adult female can carry 4000+ eggs.

Removal of adult signal: you have removed 'one' signal, you have also removed every potential signal that could have resulted from it breeding, you have also helped reduce the risk of further population spread.

Weigh up those facts please.

Oh and you have indigestion yet?

Now, unless you can find some actual peer reviewed/research based evidence supporting your theory, then please don't spout unproven, illegal and damaging ideas.

interestingly nether of the two links say a word about reintroducing Crayfish after catching

have you actually asked DEFRA if returning caught larger cray is illegal, or is it just your thoughts on the law? I have !!!!!!!!!!!!!!! i guess you dont need to, being an expert.

So surely we should all go out and trap as many signal crayfish as possible to
eliminate them. Unfortunately it’s not quite as simple as that. Trapping is good at
catching large crayfish, it is not very good at catching small crayfish. In some cases
the number of crayfish has increased following trapping, as the small ones have been
left behind to breed. Trapping cannot be used to eliminate a signal crayfish
population.
taken from the a pdf put out by the environment agency.
http/www.efishbusiness.co.uk/formsandgui...uneedtoknow.pdf.
one of quite a few saying much the same thing. add this to the haul counts of experienced trappers and it makes compelling evidence, perhaps not good enough for you. but who cares?

as i have said use smaller traps, avoid having to return the big ones by not catching them.

leave the big ones take the little ones, it may not eliminate the signal, but it seems it will help, even in a small way, to reduce their population.

sadly the signal is no longer our main problem.