Abstract
Vessel noise is an acute and chronic stressor of a wide variety of marine fauna. Understanding, modelling and mitigating the impacts of this pollutant requires quantification of acoustic signatures for various vessel classes for input into propagation models and at present there is a paucity of such data for small vessels (<25 m). Our study provides this information for three small vessels (<6 m length and 30, 90 and 180 hp engines). The closest point of approach was recorded at various ranges across a flat, ≈10 m deep sandy lagoon, for multiple passes at multiple speeds (≈5, 10, 20, 30 km h−1) by each vessel at Lizard Island, Great Barrier Reef, Australia. Radiated noise levels (RNLs) and environment-affected source levels (ASLs) determined by linear regression were estimated for each vessel and speed. From the slowest to fastest speeds, median RNLs ranged between 153.4 and 166.1 dB re 1 µPa m, whereas ASLs ranged from 146.7 to 160.0 dB re 1 µPa m. One-third octave band-level RNLs are provided for each vessel–speed scenario, together with their interpolated received levels with range. Our study provides data on source spectra of small vessels to assist in understanding and modelling of acoustic exposure experienced by marine fauna.
Highlights
Through evolutionary time, sound has become an important sensory cue for many marine taxa
Management strategies that aim to mitigate the impact of vessel noise on marine fauna [23,24,25,26,27,28] require information about source levels and vessel movements
As acoustic signals are vessel and speed specific [31,36,37,42,52], linear regression models were applied to the estimated Radiated noise levels (RNLs) and affected source levels (ASLs), to investigate the relationship between source level and speed, in the form of: SL-SLref = Cv1 × 10log10(v/vref), (2)
Summary
Sound has become an important sensory cue for many marine taxa. We lack data on the variability in noise among vessels of different classes (e.g., monohull, catamarans, tugs, landing craft) within this size range or even different passes of the same vessel This is problematic for management strategies that aim to set useful guidelines to mitigate noise for boating activities [38], in shallow coastal waters, inland waterways, and coral reefs, where small vessels have the potential to significantly change the local soundscape and, due to proximity, are more likely to affect fishes, invertebrates and small marine mammals [38,39,40,41,42]. One-third octave levels were calculated, and their propagation across the measured ranges investigated
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