Disappearing Signal Crayfish?

[peterjg]

I really hope it's not just an odd coincidence but this year I've caught a lot less signal crayfish. This is especially noticeable on my favourite stretch of the Kennet where in previous years it was not unusual to catch ten or more on a single day (absolute torture!). I don't think that I've caught more than ten all year so far and the stretch of the Kennet that I fish does not have any crayfish traps so it's not that?

It would be interesting to know if you've found the same on your waters? Are signal crayfish numbers in decline nationally? It would be great if that is the case.

 

[Philip]

Across the channel I dont have too many problems with them on my venues but I suspect if the signals are getting less then the knock on effect will be a general decrease in fish size and perhaps a larger number of smaller fish coming through.

Just a thought ...could Otters be having an impact in the UK ?.....they like a Crayfish buffet...

 

[Aknib]

I wonder if it's yet another cyclic thing?

Although i've caught my fair share of our own native whites i'd never encountered a Signal until earlier this year on the Trent, i'd been hearing rumours when I swung this alien in...

I guess the Perch 'n Chub will be packing on weight.

Pleased to hear that your burden has been lightened though, if you want 'em back just give us a shout

 

[peterjg]

Philip, there are definitely otters on the Kennet, could be a contributing factor.

 

[mikench]

I have never caught one but I do know they exist in one club water even though the club deny their presence. The traps and the guy emptying them and resetting them is a bit of a clue. I hope they are in decline, Terminal decline.

 

[S-Kippy]

I’d be very surprised ( but delighted) if they are declining. I stopped fishing the Kennet because of these damned things and it would take something exceptional to lure me back now.

 

[John Aston]

Fewer signals are visible on my local beck than for many years, but piles of crayfish shell on the Ure are testament to their abundance on a separate river system . Fewer on the Swale , I suspect, than I have seen in recent years. But I certainly would not celebrate the apparent reduction in numbers until I knew what was causing it - whatever the reason might be , it's likely it will affect other river life too .

 

[Alan Whitty]

I believe signals run on a seven year cycle, so you probably have loads of prawn sized crays, look out for a big increase in the size of your perch...

 

[ian g]

I was told the main predator for crayfish was crayfish . Never caught one myself though I assume they are in the Severn

 

[Alan Whitty]

You would know if they were there, they are a godforsaken pest, we have lots around here...

 

[chevin4]

I believe signals run on a seven year cycle, so you probably have loads of prawn sized crays, look out for a big increase in the size of your perch...

And Chub

 

[John Aston]

You would know if they were there, they are a godforsaken pest, we have lots around here...

I'm not sure I'd characterise any creature like that - signals are just products of evolution the same as the fish we near worship. Or ourselves , come to that . No animal is inherently 'bad' , and the problems that arise from signals are our fault for bringing them here in the first place ,and then failing to confine them . Signals are a concern , of course - but it is entirely our fault that they are.

There is only one 'apex predator' , the expression which is invariably misused by its application to everything from otters to killer whales. We all see an apex predator every time we look in the mirror .

 

[Alan Whitty]

Signal crayfish are a pest introduced by man in their thirst for profit, selling them for food, having no control of their spreading across most of England, a non indigenous species that carry a disease that has virtually wiped out the indigenous white claw crayfish, that is a pest, well and truly in my book, I can remember catching white clawed crayfish on the Ousel and Grand Union Canal at Leighton Buzzard, there were never many of them, nowadays I've watched signal crayfish on the bottom of the Gt.Ouse and it looks like a disturbed ants nest...

 

[GT56]

I was contacted recently by someone claiming to have permission from the EA to trap crayfish and they just need permission to place their traps on our stretch of the Trent.

As I didn't think this could be possibly true, I emailed our local EA guy who quickly replied. Stating there was no active crayfish licenses on our stretch of the Trent with non pending and I should report any sighting of crayfish traps using the EA hot line.

I believe the theory is larger crayfish eat the small ones and trappers would only take the large crayfish and return the small ones, resulting in a big population increase.

However, it's been while since I last stamped on one and I've wondered if this was due to mink.

 

[John Aston]

Just like rabbits, egrets , mink , grey squirrels , collared doves, mitten crabs, muntjac , Himalayan Balsam , zander, ide and carp signals are a fact of life here, and will remain so. Like the rest of them , they will find an ecological niche and exploit it . We successfully eradicate very few species by design - coypu are one rare example. But we are wonderful at destroying and /or polluting habitat without much regard for the consequences.

 

[mikench]

Add in rats, ferrets,and terrapins for good measure. There are cane toads in Oz, feral pigs and camels as well and in the US all because we humans have released them into the wild. At least we don’t have Burmese pythons, feral hogs and crocodiles running rampant here. Let’s not forget rhododendron is an alien species and can pollute lakes.

Rathlin: Woody the dog to become a rat catcher on NI island

Woody the dog switches his detection skills from ferrets to rats in a bid to save Rathlin's birds.

www.bbc.co.uk

 

[Alan Whitty]

Just like rabbits, egrets , mink , grey squirrels , collared doves, mitten crabs, muntjac , Himalayan Balsam , zander, ide and carp signals are a fact of life here, and will remain so. Like the rest of them , they will find an ecological niche and exploit it . We successfully eradicate very few species by design - coypu are one rare example. But we are wonderful at destroying and /or polluting habitat without much regard for the consequences.

They have found a niche, and have took advantage of many species, endangering several, that will have already had a niche, on some venues they have not overrun, however I believe the Serpentine in London has several tonnes removed annually. One club I am a member of employ a fella to trap them, the Kennet used to be alive with them, also seeing rabbits these days is a much rarer thing today than it was 35 years ago, why, I don't know, chemicals on the fields perhaps ....

 

[peterjg]

Things change, it's to be expected but not necessarily accepted. I can remember when Canada and Egyptian geese were rare, otters (saw another one only yesterday on the Thames), mink, magpies, jackdaws, our beloved kingfishers, rats, egrets, carp!, deer of any species, kites, signal crayfish, etc. Conversely things in decline: thrushes, bees, wasps, grasshoppers, hedgehogs (seen often in our garden but in decline), kestrels, sticklebacks, weasels, stoats, frogs and frogspawn, toads, honest politicians, dead flies on front of cars, greenfinch, etc.
It's probably just a local thing but numbers of signal crayfish do seem to be declining???

 

[Alan Whitty]

Otters were there before we, humans, hunted them to virtual extinction across vast swathes of the UK, so their revival is to be applauded, its just a shame that many of our rivers aren't healthy enough to sustain certain species of fish to thrive... signal crayfish however are a North American species with few predators in the UK.