Meat yields in the introduced freshwater crayfish, Pacifastacus leniusculus (Dana) and Astacus leptodactylus Eschscholtz, from British waters

The freshwater crayfish industry in Britain is based on two species, Pacifastacus leniusculus (Dana) and Astacus leptodactylus Eschscholtz, which were introduced during the 1970s and 1980s. The former is widely cultivated but both are also established in the wild, from where they are harvested. Very few studies have been made of the meat yield in these two species and none on British populations. Two essentially wild populations were assessed for their meat yield. Due to its more massive claws male P. leniusculus had a higher meat yield than male and female A. leptodactylus and female P. leniusculus in both winter and summer months. Less difference was found between the yield of tail meat between the sexes and species. Compared with other studies, meat yield in the two British populations of P. leniusculus (11–15%) and A. leptodactylus (9–13%) would appear to be lower; possible reasons for this are discussed. However, expressing meat yield as a percentage of wet body weight, although useful for comparative purposes, can give conflicting results – examples of this are given. Meat yields from the claws of the two species indicated that positive allometric growth continued after sexual maturity.     

The application of biogeographical zonation and biodiversity assessment to the conservation of freshwater habitats in Great Britain

1. Twelve biogeographical zones for freshwater habitats in Great Britain were derived, using detrended canonical correspondence analysis of data on climate, relief, geology, soils and land use, in conjunction with occurrence data for more than 300 native freshwater species. 2. The taxonomic groups used were aquatic macrophytes, dragonflies, freshwater molluscs, amphibians and selected leeches, water beetles and crustaceans. The computer database of the Institute of Terrestrial Ecology's Biological Records Centre was used as the principal source of species data. 3. Within each of the 12 biogeographical zones, 10×10 km square ‘hotspots’ for species richness and rarity were identified. 4. The significance of this work for the conservation of freshwater habitats and species in Great Britain is discussed. Copyright © 1999 John Wiley & Sons, Ltd.