With regards to May Flies: are there any altitude limitations to their range. The club I belong to are wondering if it was possible to introduce May Flies to a moor land lake we have.

That's an interesting question.
I reckon this would be a temperature thang rather than barometric pressure. The availability of silt in the river/lake bed and acidity of the water's a big factor.
Is the lake on the Denbigh moor?

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Here's one relict species that might like the upland environment - http://www.falkirk.gov.uk/services/d...ion%20plan.pdf

Introducing insects to a system is likely to involve a serious chat with the Countryside Council and the EA who will probably give you a lot of really good advice and use the term "precautionary priciple" at some stage. Give them a ring, it would great to hear what their view is.

A couple of species have become extinct in the upper Teifi and I must say it would be a great project to reintroduce them artificially. Maybe there's a similar situation on your headwaters that would justify a project that neighbouring river trusts could work on.


Check oot the disappearing Teifi species here courtesy of Graham Rutt, Ecological Appraisal Specialist, EA.

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Not a very good photo! But there are lots of these hatching out on the Headwaters of the River Taff.



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They are sill coming off in July, although a bit sporadic!

I've found mayfly in many Scottish hill lochs at altitudes of 300 ft and more.

Yes diawl bach it is on the Denbigh Moors. We were just kicking a few ideas about if it was posible to encorauge more fly life at that altitude and micro climate, that is apart from the biting midges who seem to thrive up there. A few of the local streams have a May Fly hatch lower down the Vale. Has anyone any idea what flies there are at Llyn Brenig.

Someone from the club has been in touch with the EA and have arranged to go up there in a few weeks to do some sampling/testing to: (a) See what is already up there (b) See what it could support (c) See if there are any potential habitat improvements that could be made.

Interesting you mention acidity. There used to be good hatches of Mayfly at Ladybower and Morehall, near Sheffield and the water there looked like tea at times, there was that much peat in it. It must have been quite acidic.

They tried to introduce Mayfly nymphs into Wharncliffe, Sheffield, last season, with no success. The water's more neutral and the altitude is around 850ft. It should be well silted up - it's been there over a hundred years!

I guess the two jam jars full of eggs the owner put in the 7½ acre reservoir wasn't nearly enough

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I think that a lot of it is down to having silt for the nymphs. On the Elwy the hatch can be quite localised and limited to those areas where there is a bit of silt on the bottom. Where there is silt the hatches are quite decent.

I think apart from silt the two key factors with the lake in question would be the winter temperature and the acidity and I'm not sure how they would affect the flies but it might influence where the best brood stock might be obtained as from my limited knowledge mayfly are not too keen on acidic water.

There is a lake on the Rhyl books about 5 miles away where there is a hatch of mayfly although about 200 metres lower altitude and with alkaline water. It was tested at 7.3 pH some years ago.

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