Abundance and production of the introduced signal crayfish ina British lowland river

• Published in: Aquaculture international 2000-01, Vol.8 (1), p.59
• Main Author: Guan, Rui-zhang
• Format: Article
• Language: English
• Subjects: Animal populations; Biomass; Relative abundance; Riffles; Rivers; Survival
• ISSN: 0967-6120; 1573-143X
• DOI: 10.1023/A:1009272916339

In 1984, 40 mature and 100 immature signal crayfish, Pacifastacus leniusculus (Dana), were introduced into the River Great Ouse, England. By 1994, the population had spread up and down stream to occupy an 11.4 km river section. The estimated density and biomass (wet weight) of the population in 1993 were highest in summer at 4.0 m^sup -2^ and 133 g m^sup -2^ respectively, with annual means of 2.2 m^sup -2^ and 82 g m^sup -2^ for crayfish of >30 mm carapace length (CL) in the pool (P2) where the crayfish were originally introduced. Density and biomass were 15 m^sup -2^ and 78 g m^sup -2^, with annual means of 6.1 m^sup -2^ and 33 g m^sup -2^ for crayfish of all sizes in a riffle 300 m downstream from P2. An annual survival rate of 14% was estimated for crayfish >30 mm CL in P2 in 1993. The relative abundance estimated for six riffles and six pools in 1994 showed that crayfish abundance decreased gradually from the original site of introduction both up and down the river. Estimated annual production of crayfish >35 mm CL in P2 for 1993 was 52.58 g m^sup -2^ WW, with a turnover ratio (production/biomass) of 0.44.[PUBLICATION ABSTRACT]