Thursday, 16 October 2008

Dirty But Clean Fun

Here at WTT we are always looking to innovate and share knowledge. So it was with great interest that we learned from one of our conservation project leaders about a new technique he'd been trialing.

Neville Walker is part of team of committed fishermen who are members of Gopsall Fishing Club. Over the last few years they have undertaken an ambitious programme of habitat restoration and management.

Like many lowland rivers the Scence suffers from siltation problems and each year the club undertakes a programme of gravel cleaning. This is usually undertaken using rakes and heavy high pressure water pumps. Although successful it's can be very labour intensive and some times difficult to transport equipment around on steep river banks.

By chance Neville happened to be in a local garden centre and spotted a high powered backpack leaf blower. In no time at all he a blagged a free loan and rushed off to the river to give it a whirl. The results seemed impressive and he phoned me to tell me of his latest discovery (there have been others!)

I couldn't resist the temptation to try out a new bit of kit. Thankfully I had some sponsorship for practical equipment and purchased a new Sthil leaf blower.

Soon after it was off to the Honddu (trib of Monnow) in Wales to give it a go. My friends looked on with bemusement as I donned the equipment and asked them to "fire me up!"

After a few mins we stopped and inspected what had been a heavily silted area of gravel. It had been well and truly blasted clean and to a depth suitable for trout spawning.

"Told you it would work" I stated with new found confidence!

Since then we have continued to trail the equipment on different river types. The result continue to be encouraging and we may be onto a winner. The equipment has a major advantage in that it is lightweight. On the downside at times perhaps it is a little too powerful, so restraint may be required!

Some points to note:

1) Spawning gravels are also important habitat for invertebrates and plants too and operators should avoid the temptation to clean 100% of the available spawning resource. I would recommend starting a programme of rotational jetting doing no more than 25% in any one year (4 year rotation).

2) I would always recommend you spend the winter preceding any jetting operations to identify areas were trout redds occur. This will enable you to target your time more efficiently.

3) Undertake your jetting in October prior to spawning season. On no account do it later than this or you may be causing more damage than you are trying to rectify.

4) Evaluate your efforts - are there any redds in evidence in the winter after your efforts?

5) Health & Safety - Work in pairs and use goggles/ safety glasses to protect your eyes. Undertake a risk assessment.

6) Let your local 'River Authority' know what you intend to do - you may need special permission.

7) Jetting does not solve the problems of excessive siltation. It merely mitigates against the effects. To tackle this issues effectively you must look at landuse and address problems at the catchment level.

1 comment:

Mike said...

We have used a blower on the Willow Brook for the past two years following rumours that it might work. Our experience is that on compacted gravels it needs a little help with a fork. We have fitted an 18 inch extension to the pipe which makes it more comfortable to used and certaily a lot less wet operation.