Robert D. McCauley

Unlike most capital‐breeding baleen whales that migrate between feeding and breeding grounds, the Omura's whale mainly inhabits tropical waters year‐round. This study investigated the environmental predictors of Omura's whale acoustic presence off northwest Australia by opportunistically using existing archival acoustic recordings from 2005 to 2023 from 72 deployments across 35 sites. Vocalizations were detected year‐round, and generalized additive models identified acoustic presence to be driven by habitats and environmental variables that are associated with high productivity and warmer waters. However, acoustic presence showed temporal variation linked to warmer sea surface temperatures, with higher presence during the austral summer and a distributional shift toward lower latitudes in austral winter. Proximity to shelf habitats influenced by wind‐driven upwellings, higher wind speeds, and 30‐day time‐lagged chlorophyll‐a concentrations were also significant predictors of acoustic presence, indicating that areas of high productivity, which support increased prey availability, are key habitat for the Omura's whale in northwest Australia. The results indicate Omura's whales in northwest Australia rely on predictable prey resources throughout the year and likely function as income breeders. Currently Omura's whales are listed as Data Deficient on the IUCN Red List. By understanding the distribution and predictors of Omura's whale acoustic presence, we have a foundation for future research, conservation, and management plans for the species, especially in Australian waters.

Port Phillip Bay (PPB) is a hub of trade, tourism, and biodiversity, located in the state of Victoria, along the south coast of Australia. This region facilitates the transport of ~ 1/3 of Australia’s annual container trade, provides waterscape for the state’s > 197,000 registered recreational vessels, and accommodates > 1300 species of marine flora and fauna (including the resident, critically endangered Burrunan dolphin, Tursiops australis ) within its coastal habitat. Despite its economic and ecological assets, the acoustic environment of PPB remains uncharacterised. This study presents the first assessment of key marine soundscape contributors within PPB from nine passive acoustic monitoring (PAM) stations deployed in 2021–2023. Biophony was largely attributed to snapping shrimp chorus and fish calls, with dolphin, whale, and ray vocalisations also recorded. Anthropophony associated with recreational and commercial vessels was ubiquitously identified within the soundscapes. The PAM detection range of Burrunan dolphin vocalisations was estimated for future monitoring of dolphin distribution and activity. Ambient noise levels within the species’ whistle band (5370–10,750 Hz) were assessed at each mooring location, with Burrunan dolphin detection ranges varying between sites. This study presents an integral baseline against which to monitor shifts in PPB marine soundscape composition and condition further into the Anthropocene, allowing for early detection and mitigation of acoustic threats and biophonic loss within this heavily impacted but ecologically critical marine environment.

Beaked whales are elusive deep-diving odontocetes, and their distribution and foraging ecology remain poorly documented in Australian waters. This study presents a passive acoustic monitoring (PAM)-based assessment of beaked whale foraging activity along Australia's Northwest Shelf—a continental shelf region with features typically conducive to beaked whale sustenance. The area is also of economic significance due to ongoing offshore oil and gas production, commercial fishing, and commercial shipping, raising concerns about potential impacts on these deep-diving cetaceans. This study collected year-long underwater acoustic datasets from three deep-water sites in the region. Using a semi-automated workflow based on correlogram visualizations, the study identified beaked whale foraging buzzes—short, rapid echolocation click trains associated with prey capture attempts. Analyses revealed year-round foraging activity, with significantly higher levels at night, but no strong spatial or seasonal variations across the study area. These findings suggest persistent use of the region by beaked whales despite offshore industry presence, underscoring the ecological significance of these deep-water habitats. This study highlights the value of PAM, combined with efficient analytical approaches, for monitoring cryptic species in data-limited, industrialized marine environments.

The pygmy right whale ( Caperea marginata ) is one of the least studied mysticete species. To shed light on its geographic and seasonal distribution, we compiled archival acoustic recordings from 26 sites across southern Australia and developed a deep‐learning detector for pygmy right whale “doublet” vocalizations. Seasonal patterns differed markedly between regions: On the southwestern shelf, detections consistently peaked between July and November (with an anomalous early season in March–June 2012), whereas southeastern waters exhibited more dispersed year‐round call presence, with pronounced peaks in July–October 2012, March, May–June, August, November–December 2015, June–November 2016, and February 2017. Co‐occurrence analysis of doublet and “spot” calls revealed synchronized presence/absence, supporting the hypothesis that both call types originate from the same species. Our findings underscore region‐specific habitat use and seasonal migration of pygmy right whales and highlight the value of automated acoustic techniques combined with ecological context for monitoring cryptic cetaceans in data‐limited environments.

The population of southern fin whales (Balaenoptera physalus quoyi) was severely depleted by 19th and 20th century whaling. Its conservation status remains ‘vulnerable’, as recovery has been slow. Over 19 years of underwater acoustic recordings from the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO)’s hydrophones off Cape Leeuwin, Western Australia, were analyzed to monitor fin whales’ annual migration from their Southern Ocean feeding grounds (where they spend the austral summer) to their tropical breeding grounds (where they spend the austral winter) and back. Northward migrants arrived ~2 d/y earlier (2002–2020). The number of hours with fin whale acoustic presence increased by ~49 h/y and the number of days with fin whale acoustic presence by ~3 d/y. Thus, by the end of the 19-year recording period, fin whales were acoustically present on 74 more days than at the beginning of recording. While changes in habitat function, climate, and ambient noise may affect migratory behavior, the most likely explanation is a post-whaling increase in the number of animals of this Southern Hemisphere subspecies.

The marine soundscape, whether in coastal areas or the deepest ocean, in the tropics or at the poles, contains a myriad of sounds. Sounds may be grouped by their origin into geophony (e.g., wind, precipitation, waves, earthquakes, volcanoes, and ice), biophony (e.g., invertebrates, fishes, and marine mammals), and anthropophony (e.g., port construction, mineral and hydrocarbon exploration and production, renewable energy installation, and shipping). This chapter gives a brief overview of the geophony and biophony, and then focuses on the anthropophony. The sounds of boats and ships of various types, marine seismic surveys, drilling, dredging, pile driving, windfarms, geotechnical site investigations, sonars, echosounders, explosions, and acoustic mitigation devices are presented, along with their characteristic source levels and spectra. Approaches to modeling, in particular, the sounds emitted by ships, seismic airguns, and pile driving are discussed.

This paper describes Omura's whale vocalizations recorded off northern Australia. Most common was a two-unit “doublet” (17–50 Hz, peak 25.5 Hz, duration ∼15 s). This was rhythmically repeated for extended periods of time, in typical baleen-whale song structure, suggesting it is a male breeding display. A one-unit “singlet” occurred in the lower-latitude locations off the northwest (13–72 Hz, peak 26.6 Hz, 8 s). In the Great Barrier Reef, similar doublets were detected, identifying a possible population of the species in the Southwest Pacific. Such geographic variation of song may benefit passive acoustic monitoring of this species for conservation management.

The environmental drivers of fin whale (Balaenoptera physalus) acoustic presence in Eastern Antarctic waters were investigated based on passive acoustic recordings from four sites, 2013–2019. Fin whale 20 Hz pulses were detected from late austral summer to early winter. Daily values of sea-ice concentration (SIC) were compared with the number of days with fin whale 20 Hz acoustic presence using a generalized additive model approach. At the Southern Kerguelen Plateau, Casey, and Dumont d’Urville sites, SIC correlated with fin whale calling activity, but less so at the Prydz site. Changes in SIC between sites resulted in variation in acoustic presence: Earlier sea-ice formation at Dumont d’Urville resulted in less acoustic presence in comparison to the Southern Kerguelen Plateau, where sea ice formed later in the season. Interannual variability in SIC impacted yearly acoustic presence, with a later onset of high SIC resulting in greater acoustic presence and later departure (migration timing) of the animals. Identifying the environmental drivers of fin whale presence is key to informing how this migratory species may be affected by environmental variability resulting from climate change.