scottish mayflies

[Wildfisher]

The main thing they need is a silt bottom. The nymphs are burrowers. Don't think they like acid water though.

[nant_fisher]

I was up in Assynt a couple of years ago and i'm pretty certain thats what was hatching on one of the lochs we fished.

[Malcolm]

dont they all belong to the same family? ephemeroptera?, we have syphlonurus and rithrogena
round here,these are quite large,, there are several species of danica, each species seems to be specific to an area , some of the larger ones occur in norway and sweden, breac uaig

I've had an on-off winter project going for some years now classifying the British insects without ever becoming an expert. It's a confusing business to start with and I've tried to simplify the following blurb which means I'm not being 100% accurate - never mind; here goes 

"Ephemeroptera" (literally "day wing") is an order rather than family. It is basically all the upwinged flies - these have similiar characteristics in that they all have a dun and spinner stage.

What confuses the issue with mayflies a little is that the first part of the name is the very similar "Ephemera" and the family name is "Ephemeridae".

In America the upwings are ALL known as mayflies - so the American term "mayfly" equates to Ephemeroptera rather than just Ephemeridae. As with a lot of American usages I've noticed that it's starting to take over the language and even some Brtish magazines have started to use the term "mayfly" in the American way.

In Britain the Ephemeridae includes two common species (Ephemera Vulgata and E.Danica) and one much much rarer species which (E.Lineata) is only found I believe within a few miles to the west of London. I seem to remember that there is another very rare mayfly which happens to be found in Scotland but I can't remember it's name, or where I remember that snippet from.

The Vulgata is the more common in only a few areas in England, like Gloucestershire, for the rest of Britain the predominant species is Danica and it is the species usually found in Scotland. Crocach - yours is Danica.

[Malcolm]

Another intriguing question Alan, given the distribution:Danica is widespread across the UK and Europe from Italy all the way up to Sweden you would think it unlikely. In a previous thread we looked at the lochs where there was some form of Mayfly hatch and It's clear they seem to be everywhere in Scotland - from the borders up to Caithness and Sutherland with every point in between.

They do seem to be prolific in only a few locations however and in Scotland I haven't seen the really prolific hatches except in West Sutherland and there they seem to be very localised; Borralan to Fionn and on the other side of the hill in Merkland and Griamh. Has anyone ever seen a big hatch on Shin or Assynt?

Down to environment I suppose.

   

[Malcolm]

This is what Lesley crawford said in an article

"If classifying the British mayfly is sometimes difficult, its distribution throughout this 'Sceptred Isle' has also been a subject for confusion. Whereas the southern chalkstreams and the Irish Loughs have long been noted for abundant mayfly, the fact that these insects are also well distributed across the northern highlands is frequently ignored. As mayfly larva requires a softish clay-like soil to burrow into from egg stage, it's often wrongly assumed that the apparently peaty stony rivers and lochs of Scotland do not provide suitable mayfly habitat. This is a big mistake, especially if you want to plan an angling holiday around times when larger than normal trout are to be caught.

Many highland lochs and streams contain valuable but not always visible outcrops of marl (a pale limestone mud sometimes used by farmers to `lime' their fields) and mayfly utilise this habitat to their considerable advantage. Caithness, Sutherland, Ross-shire and Argyll all have marl and mayfly present, so appearances can be very deceptive. It's also interesting that while mayfly habitat degradation is widespread in the south of England, huge numbers of mayfly continue to hatch unabated in the more pristine north" .

[zeolite]

I think there is a misconception about what influence limestone has on lochs and rivers. The limestone does not need to outcrop in the loch or river to have an influence on the pH of the waters. A smaller stream could be bringing down dissolved ions or suspended lime silt into the loch or indeed an underground spring could be pumping high pH water into the system. So you have to consider connection to limestones rather than just outcropping in the considered waters.
I believe that mayflies lay their eggs in silt and the higher the pH the better but neutral is fine. I think I have commented on how invertebrates will have their growth stunted if they have to battle the erosive effects of low pH waters.
P.A. Hillend is in the carboniferous limestone formation and there are many limestones in that. The Castlecary is one of the most famous. They used to be quarried for use in iron and steel making. The Carboniferous formations provided the resources to drive the industrial revolution. coal, steel and lime for reducing the ore.