EFFECT OF THE SOUND GENERATED BY AN ACOUSTIC HARASSMENT DEVICE ON THE RELATIVE ABUNDANCE AND DISTRIBUTION OF HARBOR PORPOISES (PHOCOENA PHOCOENA) IN RETREAT PASSAGE, BRITISH COLUMBIA

Abstract

We describe an experiment conducted to assess the impact of the sound generated by an acoustic harassment device (AHD) on the relative abundance and distribution of harbor porpoises (Phocoena phocoena) in Retreat Passage, British Columbia. During control periods when the AHD was inactive, the mean number of porpoises observed in the study area was 0.39 for broad area scans conducted with the naked eye and 0.48 for narrow sector scans conducted with binoculars. Abundance declined precipitously when the AHD was activated, to 0.007 porpoises per broad area scan and 0.018 per narrow sector scan. The mean number of porpoise resightings while tracking their movements also declined from 12.2 to 13.6 per sighting during control periods to 1.1–1.9 per sighting when the AHD was activated, which suggested that the few porpoises that ventured into the study area spent less time within it when the AHD was activated. The effect of the AHD diminished with distance. No porpoises were observed within 200 m of the AHD when it was activated. The number of sightings and resightings observed when it was activated was less than 0.2% of the number expected had there been no AHD effect at a range of 200–399 m, 1.4% the number expected at a range of 400–599 m, varied between 2.5% and 3.3% of the number expected at a range of 600–2,499 m, and was 8.1% the number expected at a range of 2,500–3,500 m, which suggested that the impact of the AHD extended beyond our maximum sighting range of 3.5 km.

Responses of harbour porpoises to pile driving at the Horns Rev II offshore wind farm in the Danish North Sea

“…Pingers have been found to deter harbour porpoises to distances of only 100 to 200 m (Kraus 1999, Barlow & Cameron 2003, Kastelein et al 2006. Seal scarers on the other hand were found to deter porpoises up to a distance of between 1 and 3.5 km (Olesiuk et al 2002, Johnston 2002. The source level of the Lofitech seal scarer as reported by the manufactures is 189 dB re 1 µPa peak whereas pile driving is considerably louder.…”

“…The effects of the seal scarer on harbour porpoises are not well known. However, Olesiuk et al (2002) 208 Table 1. Distances of POD positions (see Fig.…”

To ping or not to ping: the use of active acoustic devices in mitigating interactions between small cetaceans and gillnet fisheries

“…Studies of harbour porpoises in areas where high-intensity AHDs are deployed have shown that this species can be displaced considerable distances by high levels of sound (Johnston 2002, Olesiuk et al 2002. Also, the very clear exclusion zone shown for this species in most studies of pingers (e.g.…”

Dolphins, whales and porpoises : 2002-2010 conservation action plan for the world's cetaceans

“…Even though cetaceans may occur in heavily used harbors and be seen regularly in the vicinity of "fish farms" (Figure 9), their health may be at risk. For example, in British Columbia (western Canada), where salmon culturing is intensive and widespread, there is evidence that cetaceans are excluded from the inner reaches of bays where loud "seal scarers" are used to discourage pinnipeds from approaching salmon pens (Morton 2000;Morton and Symonds 2002;Olesiuk et al 2002). In Australia, dolphins, attracted by the concentrations of scavenging fish in the vicinity of "tuna feedlots," sometimes become entangled and die in predator-exclusion nets (Kemper and Gibbs 2001).…”