Stress level in wild harbour porpoises (Phocoena phocoena) during satellite tagging measured by respiration, heart rate and cortisol

During satellite tagging of harbour porpoises (Phocoena phocoena), heart rate, respiration rate and cortisol value were measured to evaluate stress effects during handling and tagging. Respiration rates were obtained using video recordings, heart rates were recorded and serum cortisol levels were analysed from blood samples. Differences in heart rates, respiration rates and cortisol levels before and during the tagging events were investigated. An overall significant decrease Of 31.5% in respiration rate was found during the tagging event period, while mature porpoises respired significantly more often titan immature individuals. Though significant differences in heart rates were found for some individuals, no general significant change for all animals was detected. We found no correlation between cortisol concentration and either heart rate or respiration rate, nor did we find any relationships between cortisol and month of year, sex and body length. As high individual variations occurred in response to tagging of harbour porpoises, it is not possible to give general advice based oil the factors investigated, on how to reduce stress during handling. However, pouring water over the animal and lowering it into the water seem to stabilize a stressed animal. Therefore, general precaution and individual judgement based on experience is essential when handling wild harbour porpoises.