There was a good gathering of about 18 at Grassington yesterday who spent an absorbing day considering the fate of native crayfish in the Yorkshire Dales National Park.  We were a mixed bunch of ecologists, naturalists and assortments such as me whose prime interest lies in preserving populations of natives and keeping at bay the ever encroaching tide of red signals and plague.

We began with David Rogers of the Crayfish Steering Group who put the Dales situation in the context of the UK wide situation and outlined the work being done elsewhere to preserve remaining native stock.  He painted a rather gloomy picture only briefly lightened by the considerable interest now being shown by local groups and funding bodies to tackle the complex issues that affect the survival of our British white claws.

Next up was Paul Bradley who spoke with his usual calm authority about the current population spread across the National Park and the North of England in general.  This was the first time I have seen the full position and it illustrated for me the absolutely crucial position of the Ribble catchment as a buffer between the predominant signal populations to the east and the almost undiluted native populations to the west particularly in the Lake District.  This area is the battle ground.  If we lose the Ribble to non nave species then we lose not only our remaining natives, but very much else besides.  Read on it's frightening.

Tim Thom the YDNPA ecologist gave a presentation on the conservation efforts being made to preserve some residual populations on the river Wharfe and previewed the field trip for the afternoon.  The key here is the establishment of 'Ark' sites in places that stand some chance of surviving the impact of both plague and non native species.

I talked last year about the only non native population so far discovered in the Ribble catchment at Buckill Gill a tributary of Long Preston Beck and Neil Guthrie of the EA provided the group with an update on the work done so far to eradicate this population. This was a very lucid and highly informative presentation which I won't repeat in detail because some of it is sensitive, but in essence the work planned last year to eradicate the red signals was down graded to a pilot due to the very wet weather throughout most of the summer.  This did give an opportunity to trial some of the techniques in the original plan and revisions have now been made as a result of these trials. Much additional survey work was done to establish the full spread and impact of the red signals.  It's intended to proceed with an eradication programme this summer.

Then came the, for me, real 'sit up and listen' moment when Stephanie Peay gave us the results of her survey work on Buckill Gill Beck in the context of its implications for restocking and the impact on fisheries.  Again, I will skimp on details of a very full presentation, but the key message was where you have a high density population of red signals you have nothing else.  No fish, no white claws - nothing.  We are talking here about big crustaceans that take a lot of provender. They will eat anything including fish eggs and small fish. It had been assumed that larger fish would co-exist with red signals, but the evidence here is that they do not and besides, there can be no recruitment of fish populations as no eggs or fry survive the predation.  Her survey showed a gradual decline in the mix of species as the population density of red signals rose, an inclination of non natives to move downstream of their own volition (not driven by flood action), but also a marked upstream movement as well.

The message is clear.  If red signals ever get into the Ribble from Long Preston Beck then we can kiss good by to all angling on the river and its tributaries.  Not overnight maybe and since the upstream spread is slower than that downstream then our water here at Horton will remain fishable for longer than those down river, but in time (about 5 to 10 years we will have no fish unless we move to intensive and extensive restocking without prospect of natural recruitment.  We must keep non native crayfish out of the Ribble.  It's as simple as that.

I came away to lunch more convinced than ever that not stocking our fishery makes sense.  I cannot for the life of me see why any club would wish to risk inadvertently  introducing red signals via trout stocking.  The outcome of such an accident  is truly frightening. 

I have gone on for rather too long so just to round up the day we spent the afternoon looking at the proposed site of a crayfish 'Ark' in the Wharfe catchment and discussed various issues about its establishment, publicity, public access and long term survival prospects.  The conclusion was - get on ad do it and Don't worry about making it perfect or pretty. The crayfish won't mind a bit of mess and a rather lunar landscape.

For those of you planning to fish today it's cold, but the sun is occasionally showing through the cloud.  We have no wind and just a few scattered showers.

Ian