white-clawed crayfish

White Clawed Crayfish

In Britain the white-clawed crayfish is our only native crayfish and is our largest freshwater invertebrate. It lives in clean, relatively hard, mineral-rich waters with a pH of between 7 and 9 and calcium concentrations above 5mgL -1. It is widespread in clean, calcareous streams, rivers and lakes in England but many populations have been lost since the 1970s.


The White-clawed Crayfish has now been identified as a priority species in the Biodiversity Action Plans of at least 12 planning authorities in the Yorkshire region.


As a result of legislative and conservation protocols the YNU has provided records and data on the former distribution of the White-clawed Crayfish in Yorkshire waters to a large number of planning authorities, statutory organisations, conservation bodies, academics and ecological consultancies.


Within the last decade the White-clawed Crayfish has been the subject of numerous site and river catchment surveys within the Yorkshire region, the results of which are being collated the Environment Agency.


Research paper: Gazetteer of White-clawed Crayfish in Yorkshire, by Colin Howes

Distribution map of White-clawed Crayfish from the NBN Gateway

photo by Defra

Freshwater Section Menu


R.semicolorata adult male, Malham Tarn. Credit Sharon Flint
Mayfly recording in Yorkshire


Phryganea bipunctata fermale. Credit Sharon Flint
Caddisflies or Trichoptera, (meaning, from the Greek trichos a hair and pteron a wing; hairy-wings)


Nemoura cinerea adult female, Malham fen. Credit Sharon Flint
Stonefly recording in Yorkshire


Stonefly larvae - Perla bipunctata. Credit Sharon Flint
All contacts relating to the freshwater section can be found here.


Libellula depressa - Broad-bodied chaser. Credit Sharon Flint
All the latest news for the freshwater section can

Links and Downloads

Special Links and downloads for the freshwater section:


All the latest events for the freshwater section:


iRecord Logo
Recording in freshwater habitats