Overview A small group gathered at the Ford at 7:30 pm - we did all our sampling there. The river flow was quite good for full summer, but neither abundance nor diversity were impressive. A sally under the bridge produced 3 crayfish and one was found a little further up stream; till now we had only had reports of them, apart from a big haul of much bigger ones taken at the same spot by two village boys last year. The key diagnostic item (a white spot at the junction of the claw) could not be certainly attested on every one; it is however safe to list them as American invaders.
Minute mayfly larvae and shrimps were abundant. The only other remarkable finds were a few large larvae of mayflies, a fine 3cm demoiselle nymph and a mature minnow of ca 10cm. There was no sign of molluscs, caddis larvae or water hog lice.
Details1. Results of two samplings on gravel ca.10 m above the bridge:
Crustaceans:
- A few good-sized Freshwater Shrimps (Gammarus genus), many small/v.small ones.
Insects - Mayfly larvae: very many minute nymphs; 3 large (2cm) top gill nymphs, probably Ephemera genus; 3 stubby nymphs, possibly Caenis genus (Angler’s Curse).
- One good-sized (2cm) Beetle larva (Dytiscidae family).
Worms (Annelida) - Leeches: 2 good-sized Leeches (Hirudinea class), one large (3.5 cm extended).
- Sludge Worms: 1 v. small Sludge Worm (Tubifex genus).
2. Results in muddier water near or under the bridge
Fish - 1 adult Minnow (Phoxinus phoxinus).
Crustaceans
- 4 American Signal Crayfish (Pacifastacus lenuisculus), all small (largest 5cm body length, full-grown being twice this), one with one claw missing.
Insects - I fine large Demoiselle nymph (Calopteryx genus).
