Full Description

"While a source for Chorus III has not been formally reported in Australia, one of the authors has been present at a time when several similar sounds where produced in proximity to a school of batfish. Confirmation was inferred at that time by observation of body movements simultaneously with the sound (R. McCauley, pers. obs.). Similar choruses have been detected in recordings from northwest Australia, though not in such abundance. Darwin Harbour is home to a large population of Shortfin Batfish (Zabidius novemaculeatus; Gomelyuk, 2012) considered likely to be thesourceofthis chorus."

"Chorus III (all sites) “short duration downsweep, followed by a series of short bursts increasing in intensity and frequency as the call progresses”. The calls comprised 18 bursts at a burst repetition frequency of 6.88 Hz, with pulses within these bursts occurring at 123 Hz (signal-to-noise ratio was too weak to accurately determine the number of pulses within bursts). The maximum received RMS RL and SEL for any individual calls from this chorus were 116 dB re 1 mPa and 118 dB re 1uPa^2 s. However, as with the remaining choruses, no range information was determined for these calls, thus the SL will be greater than the levels given here. This chorus was found to raise ambient noise levels over the 50–300 Hz frequency band typically to 105 dB re 1 uPa."

"When averaged acrossthestudy period, all choruses, except Choruses IV, V, and IX, commenced around or after sunset and continued for varying durations, through hours of darkness (Table 1, Figure 7)."

"Choruses I to III were comparatively short, lasting only up to 6 h, when compared with the other choruses which could last nearly 12 h (Figure 7)."

Observation Environment Quotes

"Sea-noise recordings were collected as part of the environmental monitoring of the Ichthys LNG Project in Darwin Harbour, Northern Territory,Australia."

Sound Name Quotes

"While a source for Chorus III has not been formally reported in Australia, one of the authors has been present at a time when several similar sounds where produced in proximity to a school of batfish. Confirmation was inferred at that time by observation of body movements simultaneously with the sound (R. McCauley, pers. obs.). Similar choruses have been detected in recordings from northwest Australia, though not in such abundance. Darwin Harbour is home to a large population of Shortfin Batfish (Zabidius novemaculeatus; Gomelyuk, 2012) considered likely to be thesourceofthis chorus."

"Chorus III (all sites) “short duration downsweep, followed by a series of short bursts increasing in intensity and frequency as the call progresses”. The calls comprised 18 bursts at a burst repetition frequency of 6.88 Hz, with pulses within these bursts occurring at 123 Hz (signal-to-noise ratio was too weak to accurately determine the number of pulses within bursts). The maximum received RMS RL and SEL for any individual calls from this chorus were 116 dB re 1 mPa and 118 dB re 1uPa^2 s. However, as with the remaining choruses, no range information was determined for these calls, thus the SL will be greater than the levels given here. This chorus was found to raise ambient noise levels over the 50–300 Hz frequency band typically to 105 dB re 1 uPa."

Full Description

"There aremultiplespeciesoffishthat reportedly produce sounds similar to the Chorus IV calls. West Australian dhufish (Glaucosoma hebraicum), and pearl perch (Glaucosoma bugeri), for example, produce trains of similar single pulse signals at spectral-peak frequencies between 50 and 250 Hz (Mok et al., 2011; Parsons et al., 2013c, 2014). The threadfin pearl perch (Glaucosoma magnificum) thrives in shallow waters such as those of Darwin Harbour and is known to school in large numbers in northern Australia’s tropical waters. The smaller size of the threadfin, compared with dhufish (typically maturing at 20 cm, compared with 40+ cm) would likely result in call spectral-peak frequencies higher than those of the larger pearl perches, in line with the acoustic characteristics reported here. This species is therefore a feasible source for the Chorus IV calls, though it has not been confirmed."

"Chorus IV broadband “knocking”sounds were detected predominantly at Sites 1 and 2 and to a lesser extent 3 (Table 1). It comprised short, impulsive, single pulses at reduced repetition rates compared with Choruses I and II (Figure 4). Maximum RL and SEL were 134 dB re 1 mPa and 125 dB re 1 uPa^2 s and overall, this chorus wasfoundto raise ambientnoise levelsoverthe 50–600 Hzfrequency band typically to 115 dB re 1 uPa."

Observation Environment Quotes

"Sea-noise recordings were collected as part of the environmental monitoring of the Ichthys LNG Project in Darwin Harbour, Northern Territory,Australia."

Sound Name Quotes

"There aremultiplespeciesoffishthat reportedly produce sounds similar to the Chorus IV calls. West Australian dhufish (Glaucosoma hebraicum), and pearl perch (Glaucosoma bugeri), for example, produce trains of similar single pulse signals at spectral-peak frequencies between 50 and 250 Hz (Mok et al., 2011; Parsons et al., 2013c, 2014). The threadfin pearl perch (Glaucosoma magnificum) thrives in shallow waters such as those of Darwin Harbour and is known to school in large numbers in northern Australia’s tropical waters. The smaller size of the threadfin, compared with dhufish (typically maturing at 20 cm, compared with 40+ cm) would likely result in call spectral-peak frequencies higher than those of the larger pearl perches, in line with the acoustic characteristics reported here. This species is therefore a feasible source for the Chorus IV calls, though it has not been confirmed."

"Chorus IV broadband “knocking”sounds were detected predominantly at Sites 1 and 2 and to a lesser extent 3 (Table 1). It comprised short, impulsive, single pulses at reduced repetition rates compared with Choruses I and II (Figure 4). Maximum RL and SEL were 134 dB re 1 mPa and 125 dB re 1 uPa^2 s and overall, this chorus wasfoundto raise ambientnoise levelsoverthe 50–600 Hzfrequency band typically to 115 dB re 1 uPa."

Full Description

"The fourline striped grunter (Pelates quadrilineatus) is found in Darwin Harbour and is speculated to be the source of the Chorus I calls (Gomelyuk, 2012)."

"Chorus I (all sites) was described as comprising “mid-frequency tonal grunts”, each containing an average of 51 pulses and 0.32 s duration and, in terms of energy, was the most prominent of all chorus types (see Table 1 for full details). Close calls of this chorus were ranged by the surface reflection time-of-arrival method at ≈1 m providing RMS and SEL SL estimates of 164 and 158 dB re 1 uPa^2 s, respectively, for this species. This chorus was found to raise ambient noise levels over the 1000–2000 Hz frequency band (energy from chorus frequencies <1000 Hz were removed to eliminate energy from other choruses), typically from 100 dB re 1 uPa to 125–130 dB re 1 uPa, though on occasion as high as 140 dB re 1 uPa."

"When averaged acrossthestudy period, all choruses, except Choruses IV, V, and IX, commenced around or after sunset and continued for varying durations, through hours of darkness (Table 1, Figure 7)."

"Choruses I to III were comparatively short, lasting only up to 6 h, when compared with the other choruses which could last nearly 12 h (Figure 7)."

"The GEE for the presence of Chorus 1 at Site 1 found asignificant relationship with the number of days after the new or full moon and moonphase, peaking 4–6 d after the new or full moon (Table 2, Figure 8). This pattern was also visibly discernible for Choruses II and VII (Site 1, the only site where these were detected in sufficient numbers to investigate long-term patterns; Figure 9, top left panel), while Choruses IV, V, and VIII (Sites 1 and 2) did not (Figure 9, top right panel)."

"The GEE model also determined that temperature was also significantly related to the presence of Chorus 1."

"As a result, while the GEE model for Chorus I did not show a significant relationship between presence and tidal height, it did with temperature. Furthermore, its relationship with environmental variables was evident between the number of chorus days and temperature or tide (Figure 11, top right panel)."

Observation Environment Quotes

"Sea-noise recordings were collected as part of the environmental monitoring of the Ichthys LNG Project in Darwin Harbour, Northern Territory,Australia."

Sound Name Quotes

"The fourline striped grunter (Pelates quadrilineatus) is found in Darwin Harbour and is speculated to be the source of the Chorus I calls (Gomelyuk, 2012)."

"Chorus I (all sites) was described as comprising “mid-frequency tonal grunts”, each containing an average of 51 pulses and 0.32 s duration and, in terms of energy, was the most prominent of all chorus types (see Table 1 for full details). Close calls of this chorus were ranged by the surface reflection time-of-arrival method at ≈1 m providing RMS and SEL SL estimates of 164 and 158 dB re 1 uPa^2 s, respectively, for this species. This chorus was found to raise ambient noise levels over the 1000–2000 Hz frequency band (energy from chorus frequencies <1000 Hz were removed to eliminate energy from other choruses), typically from 100 dB re 1 uPa to 125–130 dB re 1 uPa, though on occasion as high as 140 dB re 1 uPa."

Full Description

"Together with the presence of Black jewfish in Darwin Harbour, this species is suggested as the source of Chorus II (Gomelyuk, 2012)."

"Chorus II “low-frequency tonal croaks” were only detected at Site 1 and, while of shorter duration, similar to Chorus I they consisted of pulse trains and were also heard as tonal sounds. Also similar to ChorusI, aseries of ChorusII calls were detected wheretime-of-arrival techniques between direct and surface-reflected paths positioned the source at ≈1 m. At this range, the SL was estimated at 149 dB re 1 uPa and 139 dB re 1 uPa^2 s for RMS and SEL, respectively. This chorus was found to raise ambient noise levels over the 50–1000 Hz frequency band (energy from chorus frequencies >1000 Hz removed to eliminate energy from other choruses) typically to 115– 120 dB re 1 uPa, though on occasion as high as 135 dB re 1 uPa."

"When averaged acrossthestudy period, all choruses, except Choruses IV, V, and IX, commenced around or after sunset and continued for varying durations, through hours of darkness (Table 1, Figure 7)."

"The GEE for the presence of Chorus 1 at Site 1 found asignificant relationship with the number of days after the new or full moon and moonphase, peaking 4–6 d after the new or full moon (Table 2, Figure 8). This pattern was also visibly discernible for Choruses II and VII (Site 1, the only site where these were detected in sufficient numbers to investigate long-term patterns; Figure 9, top left panel), while Choruses IV, V, and VIII (Sites 1 and 2) did not (Figure 9, top right panel)."

Observation Environment Quotes

"Sea-noise recordings were collected as part of the environmental monitoring of the Ichthys LNG Project in Darwin Harbour, Northern Territory,Australia."

Sound Name Quotes

"Together with the presence of Black jewfish in Darwin Harbour, this species is suggested as the source of Chorus II (Gomelyuk, 2012)."

"Chorus II “low-frequency tonal croaks” were only detected at Site 1 and, while of shorter duration, similar to Chorus I they consisted of pulse trains and were also heard as tonal sounds. Also similar to ChorusI, aseries of ChorusII calls were detected wheretime-of-arrival techniques between direct and surface-reflected paths positioned the source at ≈1 m. At this range, the SL was estimated at 149 dB re 1 uPa and 139 dB re 1 uPa^2 s for RMS and SEL, respectively. This chorus was found to raise ambient noise levels over the 50–1000 Hz frequency band (energy from chorus frequencies >1000 Hz removed to eliminate energy from other choruses) typically to 115– 120 dB re 1 uPa, though on occasion as high as 135 dB re 1 uPa."