A dynamic approach to estimate the probability of exposure of marine predators to oil exploration seismic surveys over continental shelf waters

Abstract

The ever-increasing human demand for fossil fuels has resulted in the expansion of oil exploration efforts to waters over the continental shelf. These waters are largely utilized by a complex biological community. Large baleen whales, in particular, utilize continental shelf waters as breeding and calving grounds, foraging grounds, and also as migration corridors. We developed a dynamic approach to estimate the likelihood that individuals from different populations of blue whales Balaenoptera musculus and humpback whales Megaptera novaeangliae could be exposed to idealized, simulated seismic surveys as they move over the continental shelf. Animal tracking data for the different populations were filtered, and behaviors (transit and foraging) were inferred from the tracks using hidden Markov models. We simulated a range of conditions of exposure by having the source of noise affecting a circular area of different radii (5, 25, 50 and 100 km), moving along a gridded transect of 270 and 2500 km2 at a constant speed of 9 km h-1, and starting the simulated surveys every week of the year. Our approach allowed us to identify the temporal variability in the susceptibility of the different populations under study, as we ran the simulations for an entire year, allowing us to identify periods when the surveys would have an intensified effect on whales. Our results highlight the importance of understanding the behavior and ecology of individuals in a site-specific context when considering the likelihood of exposure to anthropogenic disturbances, as the habitat utilization patterns of each population are highly variable.

Emerging themes in Population Consequences of Disturbance models

“…This information can also be used to plan activities that avoid areas with high concentrations of marine mammals. For example, Hückstädt et al [ 48 ] used tracking data for several humpback whale and blue whale ( Balaenoptera musculus ) populations to identify which were particularly susceptible to exposure from seismic surveys and where surveys could have the largest impacts. PCoD models have been developed to be spatially explicit, using both coarse- [ 13 ] and fine-scale [ 49 ] movement data, or spatially implicit, with movement data reflected in activity budgets [ 12 ] or not included at all [ 15 ].…”

Exposure of marine megafauna to cumulative anthropogenic threats in north-west Australia

“…The exposure to both chronic and acute industrial underwater noise (e.g. recreational boating, shipping, seismic surveys, drilling, dredging and pile driving activities) is also considered a major threat to cetaceans (Avila et al, 2018;Hart et al, 2018;Hückstädt et al, 2020). These threatening processes can lead to the disruption of behaviours critical to species survival (e.g., feeding and reproduction), localised displacement from important areas, stress and potential hearing damage and mortality (McCauley et al, 2000;Gordon et al, 2003;Kamrowski et al, 2012;Hawkins et al, 2015;Nelms et al, 2016;Wilson et al, 2018;Elliott et al, 2019;Wilson et al, 2019;Dunlop et al, 2021).…”

Discrete‐space continuous‐time models of marine mammal exposure to Navy sonar

“… 2018 b ), the size of individual home ranges and the motivation underlying the use of the area of interest (e.g., whether the area contains foraging patches or is used solely for transit; Hückstädt et al. 2020 ) will all contribute to determine if each individual in a population is exposed at all and, if so, its aggregate exposure.…”