Presentation on theme: "NNMREC Behavioral Response of Harbor Porpoises to Vessel Noise in a Tidal Strait Ambient Noise and Marine Mammals May 23, 2011 Brian Polagye 1, Jason Wood."— Presentation transcript:
NNMREC Behavioral Response of Harbor Porpoises to Vessel Noise in a Tidal Strait Ambient Noise and Marine Mammals May 23, 2011 Brian Polagye 1, Jason Wood 2, Chris Bassett 1, Dom Tollit 2, and Jim Thomson 1 1 University of Washington Northwest National Marine Renewable Energy Center 2 Sea Mammal Research Unit (SMRU), Ltd.
NNMREC Tidal Energy Project Site Overview Water Depth (m) Study Site Turbine Site 3.5 m/s (7 knot) maximum currents 60 m depth Outside of commercial shipping and ferry lanes Admiralty Head Admiralty Inlet, Puget Sound, WA Source: OpenHydro
NNMREC Study Motivation Acoustic effects of tidal energy projects on marine mammal behavior are not well-understood High relative abundance of harbor porpoise in project area —Post-installation, use as a marker species Evaluate pre-installation species response to existing anthropogenic noise sources —Investigate habituation – received noise levels do not uniquely determine species response (e.g., Southall et al. 2007)
NNMREC Data Collection: AIS Vessel-Minutes AIS Receiver Turbine Site Study Site >150
NNMREC Data Collection: Sea Spider Evaluate relative presence/absence of echolocating harbor porpoise Continuous detection and logging of clicks trains to range of 200 m Train classifier (KERNO) post-processing Deployment Time: 93 days ADCP 600 kHz Hydrophone Loggerhead DSG Click Detector Chelonia CPod
NNMREC Effect of Anthropogenic Stressors Harbor porpoises expected to display avoidance to high received levels of noise —Exposures exceeding 140 dB re 1 µ Pa result in sustained avoidance (Southall et al. 2007) Use passenger ferry as a pre-installation source of opportunity —Broadband source level: 170±2 dB re 1 µPa at 1 m —Source duration in CPod range ≈ 1 minute Difficult to implement control site/study —Ferry operates 7 days/week on same schedule
NNMREC Click Train Analysis Focus on temporal trends in activity and click train properties after closest point of approach by outbound ferry 16 time series (60 minutes) duration satisfy inclusion criteria —Ferry closest point of approach must result in an average ensonification of CPod detection range to 140 dB re 1 µPa —No other vessel within 2.4 km of CPod Estimate ferry ensonification using sonar equation: —Broadband SL = 170 dB re 1µPa @ 1m —Practical spreading – N = 15 —Neglect absorption – α ≈ 0
NNMREC Ferry Acoustic Stressor Received SPL (dB re 1µPa) Measured Ferry PositionsModeled Received Levels Average ensonification by ferry at closet point of approach = 141 dB
NNMREC Strong Reaction – Activity Is there an extended period of inactivity after ferry passes? N=16 ≈20 DPM/hr (median, N=93): No Detections Positive detection latency (minutes)
NNMREC Moderate Reaction – Activity Does activity increase over time? N = 16 R 2 = 0.1, F = 5.5, p = 0.02
NNMREC Moderate Reaction – Click Properties Do mean click train properties change over time? R 2 < 0.01, F = 0.2, p = 0.7R 2 < 0.01, F = 0.2, p = 0.6 R 2 = 0.1, F = 6.2, p = 0.02R 2 = 0.04, F = 2.7, p = 0.1
NNMREC Summary Relatively high levels of porpoise activity in vicinity of proposed turbines – up to 60 detection positive minutes/hour Relatively high ambient noise from existing vessel traffic – ambient noise levels can exceed 140 dB Results suggest that local harbor porpoise population is habituated to periodic received levels ≥ 140 dB —No apparent cessation or modifications on time scales ≥ 1 minute —Less severe effects and non-vocal effects not studied Extending results to the study of tidal turbine effects —Effects may be more subtle than expected due to habituation
NNMREC Questions? Acknowledgements This material is based upon work supported by the Department of Energy and Snohomish Public Utility District under Award Number DE-FG36-08GO18179. Joe Talbert and Alex deKlerk for designing and maintaining the Sea Spider. Washington State Parks for hosting the AIS receiver and data logger.
NNMREC Receptor Response Framework Reaction Severity Response DefinitionEvaluated in Study? 7 No echolocation: severe or sustained avoidance of source No – high levels of porpoise activity in area 6 Extended cessation of echolocation clicks Yes – latency in echolocation after closest point of approach by ferry 5 Cessation or modification of echolocation clicks: duration > duration of source Yes – trends in echolocation activity and click properties after closest point of approach by ferry 4 Cessation or modification of echolocation clicks: duration ≈ duration of source No – source duration ≈ minimum resolvable time unit (1 minute) Modified version of severity scale devised by Southall et al.