Proposed Abstract Title

Mapping and Modelling Cumulative Vessel Noise in the Salish Sea

Type of Presentation

Oral

Session Title

Understanding and managing potential cumulative threats to marine mammals and their habitats from commercial vessel activities

Location

2016SSEC

Description

Commercial shipping routes in the Salish Sea pass through important habitat of a number of marine mammal species, including areas used by endangered Southern Resident Killer Whales. Cumulative noise from shipping traffic can reduce distances over which marine mammals can effectively use sound for communicating and foraging. It may also cause marine mammals to change their normal behaviours, or to avoid areas where they would otherwise be present. Mitigating the effects of underwater noise first requires an understanding of the spatial and temporal distributions of vessel noise relative to marine mammal habitat. JASCO developed a model to calculate cumulative shipping noise levels in the Salish Sea on daily and monthly time scales based on historical vessel tracking data from the Vessel Traffic Operations and Support System (VTOSS). VTOSS is based primarily upon radar and automatic identification system (AIS) vessel tracking methods. Sound propagation was computed using spatially- and seasonally-dependent environmental parameters. The sound propagation model was validated with controlled-source acoustic transmission loss measurements in the study area. Acoustic source levels for different categories of vessels were obtained from an extensive commercial vessel traffic noise dataset acquired near the Lime Kiln lighthouse in Haro Strait, and these were supplemented with dedicated measurements and with published ship noise reports. Inter-seasonal variations were addressed by considering month-long and day-periods in both winter (January) and summer (July). The outputs of the cumulative noise model consist of maps of monthly-average noise levels and daily simulations of 1-minute noise levels during a 24-hour period.

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Mapping and Modelling Cumulative Vessel Noise in the Salish Sea

2016SSEC

Commercial shipping routes in the Salish Sea pass through important habitat of a number of marine mammal species, including areas used by endangered Southern Resident Killer Whales. Cumulative noise from shipping traffic can reduce distances over which marine mammals can effectively use sound for communicating and foraging. It may also cause marine mammals to change their normal behaviours, or to avoid areas where they would otherwise be present. Mitigating the effects of underwater noise first requires an understanding of the spatial and temporal distributions of vessel noise relative to marine mammal habitat. JASCO developed a model to calculate cumulative shipping noise levels in the Salish Sea on daily and monthly time scales based on historical vessel tracking data from the Vessel Traffic Operations and Support System (VTOSS). VTOSS is based primarily upon radar and automatic identification system (AIS) vessel tracking methods. Sound propagation was computed using spatially- and seasonally-dependent environmental parameters. The sound propagation model was validated with controlled-source acoustic transmission loss measurements in the study area. Acoustic source levels for different categories of vessels were obtained from an extensive commercial vessel traffic noise dataset acquired near the Lime Kiln lighthouse in Haro Strait, and these were supplemented with dedicated measurements and with published ship noise reports. Inter-seasonal variations were addressed by considering month-long and day-periods in both winter (January) and summer (July). The outputs of the cumulative noise model consist of maps of monthly-average noise levels and daily simulations of 1-minute noise levels during a 24-hour period.