Meat yields in the introduced freshwater cray®sh, Pacifastacus leniusculus (Dana) and Astacus leptodactylus Eschscholtz, from British waters M M Harliog Ælu* & D M Holdich School of Life and Environmental Sciences, University of Nottingham, Nottingham NG7 2RD, UK Correspondence: Dr D M Holdich, School of Life and Environmental Sciences, University of Nottingham, Nottingham NG7 2RD, UK (E-mail: david.holdich@ntlworld.com) *Present address: Firat Universitesi, Su Urunleri Fakultesi, 23119 Elazig Æ, Turkey Abstract The freshwater cray®sh 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 con- ¯icting results ± examples of this are given. Meat yields from the claws of the two species indicated that positive allometric growth continued after sexual maturity. Keywords: cray®sh, freshwater, meat, yield, Britain Introduction Freshwater cray®sh are a popular, luxury food in many West European countries, with demand outstripping supply (Ackefors 1998, 1999). However, much of the production is based on introduced North American species such as the signal cray®sh, Pacifastacus leniusculus (Dana), and the red swamp cray®sh, Procambarus clarkii (Girard), which have become established in the wild or are cultured in cray®sh farms (Holdich 1993; Huner 1994a; Gherardi & Holdich 1999). In addition, the East European narrow-clawed cray®sh, Astacus leptodactylus Eschscholtz, forms an important part of the market, either as imports or from introduced populations. In Scandinavian and other north European countries, the native, noble cray®sh, Astacus astacus L., is the species of choice, but this is now more dif®cult to obtain, and consequently more expensive, due to the continuing impact of a fungal disease, cray®sh plague, which has deva- stated populations since the last century (Holdich 1999). Cray®sh products are marketed in the form of whole live, or frozen (cooked or uncooked), hard- shelled cray®sh; or fresh or frozen tail (with or without adhering hepatopancreas, known as `fat' or `butter') and claw meat (Lee & Wickins 1992). In Louisiana, whole live or frozen soft-shelled cray®sh are also produced (Huner 2001). Ovarian tissue, sometimes called `coral', may also be supplied. ã 2001 Blackwell Science Ltd 411 Aquaculture Research, 2001, 32, 411±417