No abstract

Around 176500 whales were killed in the sub-Antarctic waters off South Georgia (South Atlantic) between 1904 and 1965. In recent decades, whales have once again become summer visitors, with the southern right whale (SRW) the most commonly reported species until 2011. Here, we assess the distribution, temporal pattern, health status and likely prey of SRWs in these waters, combining observations from a summertime vessel-based expedition to South Georgia, stable isotope data collected from SRWs and putative prey and sightings reports collated by the South Georgia Museum. The expedition used directional acoustics and visual surveys to localise whales and collected skin biopsies and photo-IDs. During 76 h of visual observation effort over 19 expedition days, SRWs were encountered 15 times (~31 individuals). Photo-IDs, combined with publicly contributed images from commercial vessels, were reconciled and quality-controlled to form a catalogue of 6 fully (i.e. both sides) identified SRWs and 26 SRWs identified by either left or right sides. No photo-ID matches were found with lower-latitude calving grounds, but 3 whales had gull lesions supporting a direct link with Península Valdés, Argentina. The isotopic position of SRWs in the South Georgia food web suggests feeding on a combination of copepod and krill species. Opportunistic reports of SRW sightings and associated group sizes remain steady over time, while humpback whales provide a strong contrast, with increased sighting rates and group sizes seen since 2013. These data suggest a plateau in SRWs and an increasing humpback whale presence in South Georgia waters following the cessation of whaling.

Previous underwater recordings made in New Zealand have identified a complex sequence of low frequency sounds that have been attributed to blue whales based on similarity to blue whale songs in other areas. Recordings of sounds with these characteristics were made opportunistically during the Southern Ocean Research Partnership's recent Antarctic Blue Whale Voyage. Detections of these sounds occurred all around the South Island of New Zealand during the voyage transits from Nelson, New Zealand to the Antarctic and return. By following acoustic bearings from directional sonobuoys, blue whales were visually detected and confirmed as the source of these sounds. These recordings, together with the historical recordings made northeast of New Zealand, indicate song types that persist over several decades and are indicative of the year-round presence of a population of blue whales that inhabits the waters around New Zealand. Measurements of the four-part vocalizations reveal that blue whale song in this region has changed slowly, but consistently over the past 50 years. The most intense units of these calls were detected as far south as 53°S, which represents a considerable range extension compared to the limited prior data on the spatial distribution of this population.

No abstract

The west coast of Scotland is comprised of complex coastlines and topography, and a range of physical processes influence its coastal marine environment. The region is host to one of the highest densities of harbour porpoise Phocoena phocoena in Europe. The aim of this study was to identify habitat preferences driving the distribution of harbour porpoise, to gain a better understanding of the spatial distribution of the species in the region, as well as to assess the consistency of such patterns across time and space. Visual and acoustic line-transect surveys were conducted between 2003 and 2010. Generalised Additive Models (GAMs) with Generalised Estimating Equations (GEEs) were used to robustly determine relationships between the relative density of harbour porpoises and temporally and spatially variable oceanographic covariates. Predictive models showed that depth, slope, spring tidal range and distance to land were consistently important in explaining porpoise distribution. Consistent preferences for water depths between 50 and 150 m and highly sloped regions were observed across the temporal models. Predicted distributions revealed a consistent inshore presence for the species throughout the west coast of Scotland and confirmed that predictable oceanographic features could help inform the establishment of Special Areas of Conservation (SACs) for the species.