The behavioural response of the white-clawed crayfish (Austropotamobius pallipes) to five standard marking techniques over a 14-day period

The white-clawed crayfish (Austropotamobius pallipes), is classified as endangered in the 2010 IUCN Red List and is protected under Irish and European legislation due to a drastic decline in abundance and range over the past century. Mark-recapture methods play a vital role in the process of estimating population size, and in the monitoring and conservation of mobile species. A variety of marking techniques are routinely used in a range of crayfish species for ecological research. The majority of information on the effects of these marking techniques on the physiology of crayfish species focuses on survivability and growth, whereas information is scarce on the effects on crayfish behaviour. This study investigates the behavioural changes of crayfish in reaction to five commonly used marking techniques in laboratory conditions. The marking techniques used were internal and external passive integrated transponder (PIT) tags, visible implant elastomer (VIE) tags, cauterisation and ablation. Effects of marking technique on behaviour were evaluated immediately after marking, and over a 14-day period, on 78 crayfish. Results indicated that the internal passive integrated transponder (PIT) tags negatively affected crayfish behaviour by increasing resting levels. Ablation and cauterisation also increased grooming levels, while marking reduced activity levels in general. These effects on behaviour occurred immediately after marking, but quickly dissipated. These results suggest that the use of internal PIT tags for marking white-clawed crayfish may need to be avoided as increased resting levels could lead to increased exposure out of refuge and predation. This may have a detrimental impact on the welfare and conservation of white-clawed crayfish and also lead to biased population estimates during mark-recapture projects. The remaining marking techniques (external PIT tag, VIE tag, ablation, cauterisation) may be used, as changes in behaviour will not have a detrimental impact and therefore should not lead to biased population estimates.