Ross Culloch

Bottlenose dolphins using coastal regions adjacent to a Special Area of Conservation in north-east Scotland.

In a four year study of bottlenose dolphins along the southern shore of the outer Moray Firth we show that whilst dolphins were encountered along the majority of the survey area, there was a significant preference to the western section, which is the area directly adjacent to the current Special Area of Conservation (SAC). We also show that 80% of all groups encountered (N = 62) included calves, and that neonates were seen throughout the months of July, August, September and October. The mark-recapture abundance estimates for the southern outer Moray Firth were variable, with a highest annual estimate of 108 (95% CI = 79-129), which is similar to previous estimates for the number of animals using the entire Moray Firth. In contrast, the lowest annual estimate of 61 (95% CI = 48-74) suggests that not all individuals regularly use the entire geographical range of the population and that individual ranging patterns may vary across years. The findings of this study indicate that the southern outer Moray Firth is an important area for this population and that it should not simply be considered as a corridor to other areas of more importance. For this reason, we believe that further consideration of the current management of this population in areas outside the existing SAC is necessary.

Handling dolphin detections from C-PODs, with the development of acoustic parameters for verification and the exploration of species identification possibilities

Abstract C-PODs are static passive acoustic monitoring devices used to detect odontocete vocalizations in the range of 20–160 kHz. However, falsely classified detections may be an issue, particularly with broadband species (i.e. many dolphin species) due to anthropogenic and other noise occurring at the same frequency. While porpoise detections are verified using species-specific acoustic parameters, the equivalent does not currently exist for verifying dolphin detections. Development of such parameters would increase the accuracy of dolphin detections and eliminate the need for additional monitoring techniques or devices, reducing the cost of monitoring programmes. Herein, we present parameters based on acoustic characteristics of bottlenose (n = 29), common (n = 19) and Risso’s (n = 99) dolphin click trains, sighted within 1 km of C-PODs during land-based surveys, for in-software verification. Overlap of click train parameters among dolphin species prevented robust species identification; therefore, parameters were devised for these dolphin species collectively using frequency, inter-click interval and click train duration. A data set of 4898 Detection Positive Hours was visually verified using these parameters. The temporal and spatial patterns in the visually verified data were similar to land-based observations, suggesting the parameters operate at an acceptable accuracy. However, 68% of high-, moderate- and low-quality KERNO detections were false-positive. Our results suggest that the accuracy of classifiers and quality class weightings are site-specific, and we highlight the importance of data exploration to make the most appropriate software choices based on the aims of a study.