NOTE / NOTE Movement patterns of the invasive signal crayfish determined by PIT telemetry Damian H. Bubb, Timothy J. Thom, and Martyn C. Lucas Abstract: In one of the first field studies to utilize passive integrated transponder (PIT) telemetry to study space use of in- vertebrates, movement of the introduced signal crayfish (Pacifastacus leniusculus (Dana, 1852)) was examined intensively in a high-density population in an upland river in northern England from 18 August to 6 September 2004. Crayfish (cara- pace length 21.0–67.3 mm) were tracked with externally attached PIT tags, enabling remote detection of tagged crayfish by the use of a portable detector. Of the 406 crayfish tagged, 356 (87.7%) were subsequently relocated at least once. The majority of crayfish remained close to the release location (median distance between release and final locations 36.3 m; 25th percentile 10.4 m, 75th percentile 91.6 m). However, movements of up to 345 m were recorded. There was no rela- tionship between sex or size and distance moved. A small waterfall, upstream of the release location, appeared to form a barrier preventing movements of tagged crayfish upstream past it during the study period. PIT telemetry can provide an ef- fective method for detailed recording of space use compared with standard mark–recapture or radiotelemetry methods. Re ´sume ´: Dans l’une des premie `res e ´tudes de terrain a ` utiliser la te ´le ´me ´trie a ` transpondeur passif inte ´gre ´ (PIT) pour de ´ter- miner l’utilisation de l’espace chez un inverte ´bre ´, nous avons suivi de fac ¸on de ´taille ´e les de ´placements d’une population introduite de l’e ´crevisse signal (Pacifastacus leniusculus (Dana, 1852)) de forte densite ´ dans une rivie `re des terres hautes du nord de l’Angleterre du 18 aou ˆt au 6 septembre 2004. Des e ´tiquettes PIT fixe ´es exte ´rieurement sur les e ´crevisses (de longueur de carapace de 21,0–67,3 mm), nous ont permis de suivre les animaux a ` distance a ` l’aide d’un de ´tecteur portatif. Des 406 e ´crevisses marque ´es, 356 (87,7 %) ont e ´te ´ repe ´re ´es au moins une fois apre `s le marquage. La plupart des e ´crevisses restent pre `s du point de libe ´ration (distance me ´diane entre les points de libe ´ration et de signalisation finale de 36,3 m; pre- mier quartile 10,4 m; troisie `me quartile 91,6 m). Il y a eu cependant des de ´placements atteignant 345 m. Il n’y a pas de relation entre le sexe ou la taille de l’animal et la distance parcourue. Une petite chute, en amont du point de lib- e ´ration, semble former une barrie `re qui a empe ˆche ´ les e ´crevisses marque ´es de se disperser vers l’amont au-dela ` de ce point pendant la pe ´riode d’e ´tude. La te ´le ´me ´trie PIT s’ave `re donc e ˆtre une me ´thode efficace pour enregistrer de fac ¸on de ´taille ´e l’utilisation de l’espace par comparaison aux me ´thodes habituelles de marquage–recapture et de radiote ´le ´me ´- trie. [Traduit par la Re ´daction] Introduction An understanding of movement patterns contributing to population expansion is fundamental to a considered ap- proach of how to manage invasive species. In many groups of animals, there is a strong sex and age bias in the animals that undertake the largest movements and disperse (Hemker et al. 1984; Logan et al. 1986; Caudill 2003). The pattern of population range expansion is likely to be strongly influ- enced by these groups of animals. In crayfish, various au- thors have reported conflicting patterns of movement with sex and size (Gherardi et al. 2000; Robinson et al. 2000; Gherardi et al. 2002). The movement and dispersal of the in- vasive signal crayfish (Pacifastacus leniusculus (Dana, 1852)) are not well understood, although several studies have in- vestigated these (Abrahamsson 1981; Guan and Wiles 1997a; Kirjavainen and Westman 1999; Bubb et al. 2002a; 2004; Light 2003). The most extensive study conducted on move- ment of signal crayfish (Guan and Wiles 1997a) was lim- ited to relatively large adult crayfish; they reported no difference in movement between the sexes and no influence of size. Recently, Light (2003) reported that larger signal crayfish moved greater distances and were more likely to move downstream. Although this was based on a limited number of recaptures, it did include smaller size classes. The signal crayfish is a highly invasive species, native to Received 1 December 2005. Accepted 19 June 2006. Published on the NRC Research Press Web site at http://cjz.nrc.ca on 29 September 2006. D.H. Bubb 1 and M.C. Lucas. School of Biological and Biomedical Sciences, University of Durham, Science Laboratories, South Road, Durham, DH1 3LE, UK. T.J. Thom. Yorkshire Dales National Park Authority, Colvend, Hebden Road, Grassington, North Yorkshire, BD23 5LB, UK. 1 Corresponding author (e-mail: d.h.bubb@durham.ac.uk). 1202 Can. J. Zool. 84: 1202–1209 (2006) doi:10.1139/Z06-100 # 2006 NRC Canada