Found this nymph in a monitoring sample on a Monnow trib about a month ago. Has anyone seen spots like these? Are they natural? Or do we have a problem?



thanks

P

__________________
Trout fishermen revere the trout; trout, on the other hand, unaware of their sublime standing in man's world, revere nothing, including man, a creature they seem to view with special contempt. Nihilism is a rare trait in fish but trout are full of it. The old men liked that.

Could be Heptagenia lateralis according to my key they have little or no pattern on the body and tails.

__________________
Don't worry, be happy.
Sandy
Carried it in full, then carry it out empty.

We get a few of these on the Exe system. I don't know exactly what species it is but it is nothing to worry about!


Andy

Done a kick sample on the River Irfon recently and also found quite a few with similar markings, not seen this before in my short time kick sampling. Would certainly be interested to know what specific species of Heptagenid they are.

Sabsman.

__________________
http://micksflyfishingdiary.blogspot.com/

The nymphs of the Yellow May Dun (Heptagenia sulphurea) often have white marks on them and would be my guess at an ID.

OB

I've noticed BWO nymphs with similar markings to that heptagenid in populations where the majority of nymphs are jet black. The markings are symetrical on that specimen, something happening in the genes I'd imagine.

Quite a good camouflage on a gravelly run.

__________________
Musha rig um du rum da

Does the Yellow May nymph not have "stripey tails"?

__________________
Trout fishermen revere the trout; trout, on the other hand, unaware of their sublime standing in man's world, revere nothing, including man, a creature they seem to view with special contempt. Nihilism is a rare trait in fish but trout are full of it. The old men liked that.

Hi MrP
Yes, I agree with you that the nymphs of the Yellow May Dun would normally have a “stripy tail” as you put it; initially I thought that the water meniscus and the darkness of the specimen had affected the appearance in your photograph.

Now I’ve taken another look (with my glasses on this time!), I don’t think it’s a Heptagenid; the hind margin of the pronotum appears to have a small backward protection which would make it an Ecdyonurus. But without a very close look at the gills etc it’s not possible to be sure of the species. If I had to guess I’d suggest it’s probably E.dispar the Autumn/August Dun.

OB

thanks - good answer
Was concerned mainly about the large spots on the body, a feature I had never seen before.

Have just received a reply from Cyril Bennett who says:

"it's an Ecdyonurus species and what I call a white spot variant - very occasionally found on the chalk streams down here and possibly due to a recessive gene but I think Craig is finding them a lot more common in Scotland. See attached picture."



Interesting - just shows there's always something new if you keep your eyes open.

Patrick

__________________
Trout fishermen revere the trout; trout, on the other hand, unaware of their sublime standing in man's world, revere nothing, including man, a creature they seem to view with special contempt. Nihilism is a rare trait in fish but trout are full of it. The old men liked that.