Using the soundscape to monitor vessel visitation at an Australian fur seal (Arctocephalus pusillus doriferus) breeding colony

Abstract

Marine vessel traffic is a significant source of anthropogenic noise pollution and a major source of disturbance for many marine species. Despite Seal Rocks (Victoria, Australia) being the largest Australian fur seal breeding colony, and subject to a high volume of visitation, particularly during the breeding season, there has been no long-term effort to monitor visitation and its potential impact on seals. Autonomous passive acoustic recorders were deployed at Seal Rocks to monitor vessel visitation during both low visitation (off-peak) and the breeding (peak) season. Proportion of time vessels present in the area was calculated from visual inspection of long-term spectral averages (LTSA). Soundscape metrics were calculated to determine broadband sound pressure level (BL) and percentiles of power spectral density (PSD). Visitation was higher in the peak season, as was BL, particularly during daylight hours. While there were periods of high winds and heavy swell during both deployment seasons, vessel noise was still a regular and loud contributor to the soundscape. From these results, the airborne noise received by seals can also be estimated. These results will contribute towards the development of an impact model to assess noise impacts at Seal Rocks and other sensitive marine sites.