The T-POD (Timing POrpoise Detector) is a self-contained acoustic data logger used for detecting and monitoring the presence of echolocation clicks of small cetaceans. It has become a standard tool in environmental impact assessments and monitoring programmes. Yet, little is known about the variability in sensitivity and detection range of T-PODs. In this study the field performance of ten v3 T-PODs was compared to detection thresholds measured in a tank. The T-POD thresholds ranged from 123 to 132 dB re 1μPa (pp). The detection thresholds of the ten individual T-PODs were different and the differences increased over time. The more sensitive a T-POD was in the laboratory (i.e. the lower the threshold) the more clicks were recorded by it in the field. Threshold correlated differently to the five analysed T-POD parameters (encounters, encounter duration, waiting time, porpoise positive minutes, clicks per porpoise positive minute). This study demonstrates that individual threshold calibrations of T-PODs are necessary to obtain comparable results when monitoring odontocetes with this tool. Regression equations for relationships between T-POD detection thresholds and study parameters obtained during field trials may allow comparisons of T-PODs with different detection thresholds.

Seabirds are important components in marine ecosystems. However, knowledge of their ecology and spatial distribution during the non-breeding season is poor. More investigations during this critical period are required urgently, as marine environments are expected to be profoundly aVected by climate change and human activities, with both direct and indirect consequences for marine top predators. Here, we studied the distribution of little auks (Alle alle), one of the most abundant seabird species worldwide. We found that after the breeding season, birds from East Greenland quickly travelled north-east to stay for several weeks within a restricted area in the Greenland Sea. Activity patterns indicated that Xying behaviour was much reduced during this period, suggesting that this is the primary moulting region for little auks. Birds then performed a southerly migration to overwinter oV Newfoundland. These preliminary results provide important information for the conservation of this species and emphasise the need for further studies at a larger spatial scale.

Several studies have shown that pingers mitigate porpoise bycatch and thus pinger use is now mandatory in some fisheries -although the long-term effects of pinger exposure on porpoises have not been well studied. The effects of 2 types of pingers (Airmar: 10 kHz tone; SaveWave Black Saver: 30−160 kHz sweep) on the presence of wild harbour porpoises, Phocoena phocoena, were investigated in 2 areas. Pinger spacing within the areas was similar to that used in commercial fisheries. Two scenarios were tested: (1) pingers were periodically activated and deactivated during 6 periods resembling the deployment and recovery of nets in a gillnet fishery, and (2) pingers were active continuously for 28 d. Acoustic dataloggers (T-PODs) were deployed, 4 within the pinger areas and 3 in control areas, and detected porpoise echolocation activity throughout the entire study. During the periodic-exposure scenario, the porpoise detection rate was reduced by 56% when pingers were active. The reduction was larger for the SaveWave pingers (65%) than for the Airmar pingers (40%). There was a tendency for the encounter rate to increase after the first 2−4 periodic exposures, which could indicate gradual habituation. During the continuous-exposure scenario, the detection rate was reduced by 65% throughout the 28 d with no sign of habituation. In the control areas (2.5, 3 and 5 km distant), neither a decrease nor an increase in detection rate was observed, suggesting that porpoises were displaced either < 2.5 km or > 5 km away. If pingers are used as deterrent devices, the impact of habitat exclusion must therefore be considered concurrently with mitigation of bycatch, especially when regulating fisheries in Marine Protected Areas.