Movement patterns of the invasive signal crayfish determined by PIT telemetry

In one of the first field studies to utilize passive integrated transponder (PIT) telemetry to study space use of invertebrates, 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 (carapace 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 relationship 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 effective method for detailed recording of space use compared with standard mark-recapture or radiotelemetry methods.