Miles Parsons

In situ source levels of mulloway (Argyrosomus japonicus) calls

Mulloway (Argyrosomus japonicus) in Mosman Bay, Western Australia produce three call categories associated with spawning behavior. The determination of call source levels and their contribution to overall recorded sound pressure levels is a significant step towards estimating numbers of calling fish within the detection range of a hydrophone. The source levels and ambient noise also provide significant information on the impacts anthropogenic activity may have on the detection of A. japonicus calls. An array of four hydrophones was deployed to record and locate individual fish from call arrival-time differences. Successive A. japonicus calls produced samples at various ranges between 1 and 100 m from one of the array hydrophones. The three-dimensional localization of calls, together with removal of ambient noise, allowed the determination of source levels for each call category using observed trends in propagation losses and interference. Mean source levels (at 1 m from the hydrophone) of the three call categories were calculated as 163 ± 16 dB re 1 μPa for Category 1 calls (short call of 2-5 pulses); 172 ± 4 dB re 1 μPa for Category 2 calls (long calls of 11-32 pulses); and 157 ± 5 dB re 1 μPa for Category 3 calls (series of successive calls of 1-4 pulses, increasing in call rate).

Fish choruses off Port Hedland, Western Australia

Abstract Australian waters are home to a number of vocal species of fish. Cataloguing the acoustic characteristics and temporal patterns of choruses and their locations can provide significant information for long-term monitoring of vocal fishes and their ecosystems. In coastal waters off Port Hedland, Western Australia, two seafloor positioned sea-noise loggers, located 21.5 km apart in 8 and 18 m of water, recorded for an 18-month period. Numerous sound sources were detected, including mooring and vessel noise, humpback whale song and a large variety of fish signal types. Seven fish choruses were identified, occurring predominantly between late spring and early autumn (wet season) and displaying energy from 50 Hz to >4 kHz. Many of these choruses exhibited acoustic characteristics similar to choruses previously reported elsewhere, for some of which the source species or families have been identified. Distinct diurnal patterns in the choruses were observed, associated with sunrise or sunset and in some cases, both. While choruses were predominantly recorded on different days, there were at total of 80 days when more than one chorus was present at the same site. Some pairs of choruses present on the same day exhibited various combinations of temporal and frequency partitioning, while others displayed predominant overlap in both spaces.

Non-song vocalizations of pygmy blue whales in Geographe Bay, Western Australia

Non-song vocalizations of migrating pygmy blue whales (Balaenoptera musculus brevicauda) in Western Australia are described. Simultaneous land-based visual observations and underwater acoustic recordings detected 27 groups in Geographe Bay, WA over 2011 to 2012. Six different vocalizations were recorded that were not repeated in a pattern or in association with song, and thus were identified as non-song vocalizations. Five of these were not previously described for this population. Their acoustic characteristics and context are presented. Given that 56% of groups vocalized, 86% of which produced non-song vocalizations and 14% song units, the inclusion of non-song vocalizations in passive-acoustic monitoring is proposed.

Source levels of dugong (dugong dugon) vocalizations recorded in Shark Bay

Dugongs (Dugong dugon) spend significant time in shallow, turbid waters and are often active at night, conditions which are not conducive to visual cues. In part, as a result, dugongs vocalize to gain or pass information. Passive acoustic recording is a useful tool for remote detection of vocal marine animals, but its application to dugongs has been little explored compared with other mammals. Aerial surveys, often used to monitor dugong distribution and abundance, are not always financially or logistically viable and involve inherent availability and perception bias considerations. Passive acoustic monitoring is also subject to sampling biases and a first step to identifying these biases and understanding the detection or communication range of animal calls is to determine call source level. In March 2012, four dugongs were fitted with satellite tags in Shark Bay, Western Australia by the Department of Environment and Conservation. During this, acoustic recordings were taken at 5.1 m range. Source levels for each of five call types (two types of chirp, bark, squeak, and quack) were estimated, assuming spherical spreading as the transmission loss. Mean source levels for these call types were 139 (n = 19), 135 (12), 142 (2), 158 (1), and 136 (9) dB re 1 μPa at 1 m, respectively.

Soundscape diversity in the Great Barrier Reef: Lizard Island, a case study

Abstract Passive acoustic monitoring can provide valuable information on coral reefs, and examining the acoustic attributes of these ecosystems has the potential to provide an insight into their status and condition. From 2014 to 2016, a series of underwater recordings were taken at field sites around Lizard Island in the Great Barrier Reef, Australia. Six individual fish choruses were identified where each chorus displayed distinct acoustic characteristics. Choruses exhibited diurnal activity and some field sites displayed consistently higher diversity of choruses and levels than others, suggesting that particular locations are important aggregation areas for soniferous fish species. During peak activity, choruses were a prominent component of reef soundscapes, where received levels of a chorus reached upwards of 120 dB re 1μPa rms over the 450–650 Hz band, equating to a 40 dB increase above ambient noise levels of ≈80 dB re 1μPa rms. Three out of the six detected choruses exhibited spectral and temporal characteristics similar to choruses previously documented at these sites and elsewhere, produced by planktivorous fish species. Three of these choruses appear to be undocumented and could hold information on the presence, abundance and dispersal patterns of important fish species, which may have potential long-term management applications. Future research should focus on extricating the temporal patterns associated with bioacoustic activity and determining the potential environmental drivers of biological choruses. Additionally, developing appropriate techniques for direct identification of vocalizing species would strongly increase the management applicability of passive acoustic monitoring.

Spatial and Temporal Variation in the Acoustic Habitat of Bottlenose Dolphins (Tursiops aduncus) within a Highly Urbanized Estuary

There is growing awareness of underwater noise in a variety of marine habitats, and how such noise may adversely affect marine species. This is of particular concern for acoustically-specialised species, such as dolphins. In order to ascertain the potential impacts of anthropogenic noise on these animals, baseline information is required for defining the soundscape of dolphin habitats. The Swan-Canning River system in Western Australia flows through the city of Perth, and experiences numerous anthropogenic activities. Despite this, the river system is home to a community of Indo-Pacific bottlenose dolphins (Tursiops aduncus). To provide a baseline soundscape description of dolphin habitat, over 11,600 h of acoustic data were analysed from five sites within the Swan River (from Fremantle Inner Harbour to 20 km upstream) across an eight-year period. Multiple sound sources were recorded at these sites, including: snapping shrimp; fishes; dolphins; pile-driving; bridge and road traffic; and vessel traffic. The two most prevalent sound sources, vessel traffic and snapping shrimp, likely have very different effects on dolphin communication with the former expected to be more disruptive. Sites were characteristic in their prominent sound sources, showing clear among-site variations, with some sites being ‘noisier’ than others based on broadband noise levels, octave-band noise levels, and power spectrum density percentiles. Perth Waters had the highest broadband noise (10 Hz – 11 kHz; mean 113 dB re 1 µPa rms), whilst Heirisson Island was quietest (mean 105 dB re 1 µPa rms). Generalised estimating equations identified variation in broadband noise levels within sites at a fine temporal scale, although sites differed in the significance of temporal variables. At Mosman Bay, a long-term dataset spanning eight years highlighted inter-annual variation in broadband noise levels, but no overall upwards or downwards trend over time. Acoustic habitats of the Swan River displayed significant variations at a variety of temporal and spatial scales, throughout areas frequented by the local dolphin community. Such variations should be quantified when assessing dolphin acoustic habitat as they may provide significant clues to dolphin behaviour.

Long-term monitoring of soundscapes and deciphering a usable index: Examples of fish choruses from Australia

Similar to geophysical and anthropogenic noise, biological contributions to soundscapes vary considerably in frequency, time, and intensity. Fish choruses are a perfect example, contributing significantly to marine biological noise and are used here as an analogue for variations in soundscapes. Their species-characteristic signals vary thus, so do their choruses, which can raise ambient noise levels by up to tens of decibels, for prolonged periods. Multi-species choruses can occur, with varying degrees of temporal and frequency partitioning, or none at all. Australian datasets of underwater noise have been acquired for nearly two decades and multiple fish calling patterns have been detected. Detecting, delineating, and understanding these patterns is non-trivial and a metric relating their contribution to the soundscape with biodiversity or habitat would be an invaluable tool. In recent years, several acoustic indices have been derived, proving useful in the terrestrial domain. Investigation of their appl...

Spatio-temporal patterns in underwater sound within an urban estuarine river

Underwater noise environments are increasingly being considered in marine spatial planning and habitat quality assessments, particularly with regard to acoustically specialised fauna. The Swan River in Western Australia flows through the state capital of Perth and consequently experiences a range of anthropogenic activities. However, the river is also extensively used by a resident community of bottlenose dolphins (Tursiops aduncus). This study aimed to describe underwater sound sources within the Swan River, examine spatial and temporal soundscape variability, and determine dolphin responses to noisy environments. Acoustic datasets collected from 2005 to 2015 indicated that the Swan River was comprised of multiple acoustic habitats, each with its own characteristic soundscape and temporal patterns in underwater noise. The anthropogenically “noisiest” site was the Fremantle Inner Harbour (mean broadband noise level: 106 dB re 1 μPa rms [10 Hz–11 kHz]); yet dolphins remained present in this area even at high vessel densities. However, fine-scale analyses indicated significant alterations to dolphin behavior at high vessel densities and to dolphin whistle characteristics in high broadband noise conditions. These results highlight the need to consider spatial and temporal patterns when assessing the composition of underwater soundscapes, and identify potential responses of coastal dolphins to busy, noisy environments.Underwater noise environments are increasingly being considered in marine spatial planning and habitat quality assessments, particularly with regard to acoustically specialised fauna. The Swan River in Western Australia flows through the state capital of Perth and consequently experiences a range of anthropogenic activities. However, the river is also extensively used by a resident community of bottlenose dolphins (Tursiops aduncus). This study aimed to describe underwater sound sources within the Swan River, examine spatial and temporal soundscape variability, and determine dolphin responses to noisy environments. Acoustic datasets collected from 2005 to 2015 indicated that the Swan River was comprised of multiple acoustic habitats, each with its own characteristic soundscape and temporal patterns in underwater noise. The anthropogenically “noisiest” site was the Fremantle Inner Harbour (mean broadband noise level: 106 dB re 1 μPa rms [10 Hz–11 kHz]); yet dolphins remained present in this area even at hi...

Underwater sound pressure and particle motion (acceleration, velocity, and displacement) from recreational swimmers, divers, surfers, and kayakers

Naturally constrained environments like bays and lakes are frequently used for water sports activities. While the sound of motorized vessels is rather well understood, non-motorized activities have received less investigation. Ten water sports activities (swimming backstroke, breaststroke, butterfly, and freestyle; snorkelling with fins; kicking a boogie board with fins; paddling with alternating or simultaneous arms while lying on a surfboard; scuba-diving; kayaking and jumping into the water) were recorded in a controlled yet even more constrained environment: an Olympic-sized pool. Activities that occurred at the surface involved repeatedly piercing the surface and hence creating the bubble clouds which were the strongest sound generators. Received levels were 110–131 dB re 1μPa (10–16,000 Hz) for all of the activities at the closest point of approach (1 m). All activities produced a characteristic spectro-temporal pattern in all the quantities measured (sound pressure, particle displacement, velocity,...

Patterns of biophonic periodicity on coral reefs in the Great Barrier Reef

The coral reefs surrounding Lizard Island in the Great Barrier Reef have a diverse soundscape that contains an array of bioacoustic phenomena, notably choruses produced by fishes. Six fish choruses identified around Lizard Island exhibited distinctive spatial and temporal patterns from 2014 to 2016. Several choruses displayed site fidelity, indicating that particular sites may represent important habitat for fish species, such as fish spawning aggregations sites. The choruses displayed a broad range of periodicities, from diel to annual, which provides new insights into the ecology of vocalising reef fish species and the surrounding ecosystem. All choruses were affected by one or more environmental variables including temperature and moonlight, the latter of which had a significant influence on the timing and received sound levels. These findings highlight the utility of passive acoustic tools for long-term monitoring and management of coral reefs, which is highly relevant in light of recent global disturbance events, particularly coral bleaching.