BBC1 Countryfile 19.00 !

[Gerry Giles]

well worth watching lincolnshire ....>Ellie also sees how eels are being used to combat the threat from invasive signal crayfish

 

[Mark Swaby]

Used to use crayfish as bait all the time when i was young, caught mostly pike ,chub and the odd Barbel but never an eel. Very concerned with them returning an Invasive species too, its up to 6 months in prison and a £10,000 fine in the UK. The piece smacked of scientists making up a project to get funding. Joining crayfish with declining Eel numbers would be exactly down the right route for a grant .I wonder how much money is being wasted on this project that could be better used. The Lady could not even give them a straight answer when asked if it was successful.

 

[Howard Cooke]

Agree Mark. It was all a bit unconvincing. It’s probably just me, but I cant see how your average sized eel could easily consume an average sized crayfish, unless it has python/anaconda type characteristics. And when I think about the frightening numbers of crayfish in the Kennet, how many eels would need to be introduced to make any kind of difference. At least it highlighted the big impact crayfish burrowing activity has on the river.

I was also reflecting on the delicate way she was treating the crayfish being subjected to scientific testing. Very gentle and clearly eager to minimise discomfort. This is in sharp contrast to the treatment I frequently dished out when hooking one of the little sods.

 

[Joe Winstanley]

You are a cynical bunch..

Numerous papers on control of the signal crayfish in the UK have highlighted the potential for various forms of biological control, including predation by eels. Research elsewhere (see link below as an example) has highlighted the potential, so it makes complete sense for this to be investigated in the UK. In fact when you look at the results of the French study below, you might well ask why it took two years for similar work to be kicked off in the UK.

This particular study is being funded jointly by the EA and Loughbrough, as part of a PhD studentship worth £14,296 per annum over the three years of the project, hardly big money compared to the potential benefits.

I thought the reasons for releasing the crayfish back into the Bain were pretty obvious, catching them and killing them would completely undermine the efficacy of the study. I also thought she was pretty clear about the projects success, much more than I would have expected given there is another 6 months to run.

(PDF) Native European eels as a potential biological control for invasive crayfish

PDF | Invasive species may have strong negative impacts on ecosystems. Invasive crayfish are well known to cause ecological imbalances in freshwater... | Find, read and cite all the research you need on ResearchGate

www.researchgate.net

 

[Graham Shaw]

Agree Mark. It was all a bit unconvincing. It’s probably just me, but I cant see how your average sized eel could easily consume an average sized crayfish, unless it has python/anaconda type characteristics.

The study linked by Joe is very convincing in its conclusions:

Isotopic analysis results highlighted that all weight
classes of P. clarkii were subject to predation by eels. As
reported in previous studies, smaller crayfish were most
strongly preyed upon regardless of predator size (Engl-
und & Krupa, 2000; Aquiloni et al., 2010). In our study,
larger crayfish (>25 g) became more important in the
diet of the largest fish, mainly because eels are gape-lim-
ited. As observed in a laboratory experiment, adult cray-
fish are vulnerable to eels when crayfish are soft-shelled
during the moulting period in open water (Aquiloni
et al., 2010).

However, that French study is of eels eating the Swamp crayfish (up to 12cm excl claws), as opposed to the Signal crayfish (up to 16cm body length excl. the massive claws)

So let's hope that the eels would eat most of the Signals before they reached big male adult size!

It's also important to note that the eel population in the ponds studied was considered to be "at maximum density" in order to reduce a dense crayfish population.

 

[Terry Harman]

I’m all for it ...introduce more and fatten up the eels and the otters might leave the barbel alone

 

[Paul Collins]

Allegedly,
European crayfish were deliberately stocked into Aldenham reservoir and very soon had reached the Colne / Ver and all through the Colne valley to the Thames. Including nearby gravel pits including my club's at Park Street.
Overnight they all died off, I'm told throughout the whole valley.
This may be linked to the Signals gaining a foothold and infecting them with something but something definitely killed off the Europeans.
Research into something similar that affects Signals should be encouraged in my opinion.

 

[Mark Anderson]

Hi men,

I spoke to a couple of Oxford uni students doing a study on our precious stretch of the windrush , post otter destruction . They said the signals had such a hold the only way they could see a way to change it was Arking it ??? . That's where they kill everything and start again . Not sure they grasped the magnitude of what they were saying . This program looked like a vehicle for showcasing a theory .

Hatter

 

[Paul Collins]

IIRC, it's been successfully done in Norway when escaped farmed Salmon were infesting the gene pool of the indigenous population.

 

[Jason Bean]

Hi men,

I spoke to a couple of Oxford uni students doing a study on our precious stretch of the windrush , post otter destruction . They said the signals had such a hold the only way they could see a way to change it was Arking it ??? . That's where they kill everything and start again . Not sure they grasped the magnitude of what they were saying . This program looked like a vehicle for showcasing a theory .

Hatter

I never thought it would happen but most of the rivers in oxford have very few signal crayfish in them now, why that is we don't know. the only obvious conclusion is otters. just hope it stays that way.

 

[Mark Swaby]

Signal crayfish are supposed to be susceptible to white spot syndrome virus. The signal crayfish also carry the crayfish plague that kills off our native white clawed species. Stress can kick start the plague and the signal crayfish will also die off. Obviously research would need to be done by a company like CABI in Egham to check that the virus does not effect our native shrimp, or what type of stress is effective to trigger the plague.

 

[Mark Anderson]

Hi men,

Jason, my spies in Oxford have still had problems on the Thames , perhaps it starts with the smaller rivers . Hope it spreads to my local canal where it's crayfish soup .

Even up in the water maggot fishing for perch , and they are real units as well .

Hatter