Nowhere to go: noise impact assessments for marine mammal populations with high site fidelity

Abstract

As awareness of the effects of anthropogenic noise on marine mammals has grown, research has broadened from evaluating physiological responses, including injury and mortality, to considering effects on behavior and acoustic communication. Most mitigation efforts attempt to minimize injury by enabling animals to move away as noise levels are increased gradually. Recent experiences demonstrate that this approach is inadequate or even counterproductive for small, localized marine mammal populations, for which displacement of animals may itself cause harm. Seismic surveys within the ranges of harbor porpoise Phocoena phocoena in California and Mā ui dolphin Cephalorhynchus hectori maui in New Zealand highlight the need to explicitly consider biological risks posed by displacement during survey planning, monitoring, and mitigation. Consequences of displacement are poorly understood, but likely include increased stress and reduced foraging success, with associated effects on survival and reproduction. In some cases, such as the Critically Endangered Mā ui dolphin, displacement by seismic activities risks exposing the remaining 55 dolphins to bycatch in nearby fisheries. Similar concerns about military and industrial activities exist for island-associated species such as melon-headed whales Peponocephala electra in Hawai'i; shelf-break associated species such as Cuvier's beaked whales Ziphius cavirostris off the US Atlantic coast, and whales foraging in coastal habitats, such as the Critically Endangered western gray whale Eschrichtius robustus. We present an expanded framework for considering disturbance effects that acknowledges scientific uncertainty, providing managers and operators a more robust means of assessing and avoiding potential harm associated with both displacement and direct effects of intense anthropogenic noise exposure.

Acoustic monitoring reveals the times and tides of harbor porpoise (Phocoena phocoena) distribution off central Oregon, U.S.A.

“…Furthermore, baseline information on the distribution and habitat usage of coastal species is often limited. Further, existing data are often only available at spatial and temporal scales much larger than what is needed to adequately inform regulatory decisions for fine-scale activities, including marine energy, seabed mining and point source pollution (Forney et al 2017). Knowledge of cetacean distributions and habitat use at finer, site-specific scales is crucial to answer management questions and capture relevant habitat heterogeneity (Wiens 1989, Tett et al 2013.…”

Impacts of Navy Sonar on Whales and Dolphins: Now beyond a Smoking Gun?

“…It should be noted, however, that the degree of responses by animals, and the received level of sound at which these responses occur, might be affected by the context in which the sound is received. For example, a mother and calf might be more "skittish" than a solitary male; an animal that urgently needs to feed may show less of a behavioral change than one that is relatively well-fed; a young animal that is more vulnerable to predation might react more quickly to an intense noise than a larger adult; a habituated animal might respond at higher received levels than a naive animal; or a chronically stressed animal might responded differently to a nonstressed animal (see section Absence of Evidence Does Not Mean Evidence of Absence-the Need For Precaution Below; Beale and Monaghan, 2004;Beale, 2007;Wright et al, 2007;Guerra et al, 2014;Forney et al, 2017).…”

“…A stressed, starving or sick animal may not display any observable response if they do not have the energy or capability to react behaviorally; for example, if the disturbance location is the only viable feeding area, the animal may not leave (Beale and Monaghan, 2004;Beale, 2007;Wright et al, 2007;Forney et al, 2017). In short, absence of a behavioral response to noise does not necessarily translate to absence of a significant or lifethreatening impact.…”

Unexpected patterns of global population structure in melon-headed whales Peponocephala electra

“…MHWs appear to be particularly sensitive to anthropogenic sound (Southall et al 2006, Brownell et al 2009b), a fact that has been exploited in many parts of the world in drive hunts where sound is used to drive MHWs toward the beach where they can be more easily killed or captured (Brownell et al 2009a). The limited range of the Kohala coast population limits their ability to move away from harmful sound sources, and increases the risk that they will be displaced into unfavorable or unfamiliar habitat if they do (Forney et al 2017). Thus, the unique characteristics of the Kohala resident population combined with their proximity to a known threat warrant additional conservation and management attention for this small, demographically independent population.…”