Crayfish management

Signal crayfish, an invasive aquatic species, are present throughout mainland UK and have severe negative effects on other aquatic biota. While no effective mechanism for their eradication exists, control attempts often make use of removal by trapping. An experiment to examine the effectiveness of such trapping in rivers in the Upper Thames was designed. In spite of removing huge numbers (e.g. 6000 individuals from 200 m of river), densities were at least partially restored by immigration from untrapped areas. In removal areas the remaining crayfish gained weight; a potentially negative impact of removals. However, the remaining crayfish also moved less, suggesting that trapping at the edge of a population may delay colonization of new waters. Moreover numbers of individuals and taxa of non-crayfish macroinvertebrates were substantially higher where removals had occurred. These latter findings suggest that crayfish control attempts, while unlikely to achieve eradication, may nevertheless provide some conservation benefits.

Tom P. Moorhouse
David W. Macdonald


Moorhouse TP, Macdonald DW. The effect of removal by trapping on body condition in populations of signal crayfish. Biol Conserv. 2011;144(6):1826-31. doi: 10.1016/j.biocon.2011.03.017. PubMed PMID: WOS:000292661100006.

Moorhouse TP, Macdonald DW. Immigration rates of signal crayfish (Pacifastacus leniusculus) in response to manual control measures. Freshw Biol. 2011;56(5):993-1001. doi: 10.1111/j.1365-2427.2010.02528.x. PubMed PMID: WOS:000289171400016.

Moorhouse TP, Macdonald DW. The effect of manual removal on movement distances in populations of signal crayfish (Pacifastacus leniusculus). Freshw Biol. 2011;56(11):2370-7. doi: DOI 10.1111/j.1365-2427.2011.02659.x. PubMed PMID: ISI:000296061400013.

Moorhouse TP, Macdonald DW. Are invasives worse in freshwater than terrestrial ecosystems? Wiley Interdisciplinary Reviews: Water. 2015;2(1):1-8.

Moorhouse TP, Poole AE, Evans LC, Bradley DC, Macdonald DW. Intensive removal of signal crayfish (Pacifastacus leniusculus) from rivers increases numbers and taxon richness of macroinvertebrate species. Ecology and Evolution. 2014;4(4):494-504. doi: 10.1002/ece3.903.

Harvey GL, Henshaw AJ, Moorhouse TP, Clifford NJ, Grey J, Holah H, et al. Invasive crayfish as drivers of fine sediment dynamics in rivers: field and laboratory evidence. Earth Surface Processes and Landforms. 2014;39(2):259-71. doi: 10.1002/esp.3486.

Harvey GL, Moorhouse TP, Clifford NJ, Henshaw AJ, Johnson MF, Macdonald DW, et al. Evaluating the role of invasive aquatic species as drivers of fine sediment-related river management problems: The case of the signal crayfish (Pacifastacus leniusculus). Prog Phys Geogr. 2011;35(4):517-33. doi: Doi 10.1177/0309133311409092. PubMed PMID: ISI:000292888900005.