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SURTASS LFA
SURTASS LFA

MONITORING/RESEARCH TO INCREASE UNDERSTANDING OF THE POTENTIAL EFFECTS OF SURTASS LFA SONAR TRANSMISSIONS ON BEAKED WHALES AND/OR HARBOR PORPOISES

A new monitoring and research provision was included in the 2012 MMPA Final Rule and subsequent annual LOAs for SURTASS LFA sonar that required the Navy to consider research or monitoring strategies that would increase the understanding of the potential effects of SURTASS LFA sonar transmissions on beaked whales and/or harbor porpoises. The Navy's first step in this effort was to convene a group of recognized scientific subject matter experts in the fields of marine bio-acoustics, marine mammal biology and hearing, and marine behavioral sciences to evaluate and recommend possible research or monitoring efforts. The goal of this Scientific Advisory Group (SAG) was to specifically evaluate and recommend a practical strategy for the Navy on the possible monitoring and research efforts it could undertake to provide information on how exposure to SURTASS LFA sonar might affect the behavior of beaked whales and/or harbor porpoises.

The Navy organized a group of renowned marine scientists and bio-acousticians to form the SAG, which included:

  • Dr. Christopher W. Clark
  • Dr. Daniel P. Costa
  • Dr. William T. Ellison
  • Dr. Jason Gedamke
  • Dr. Ronald A. Kastelein
  • Dr. Brandon L. Southall (chair)

  • The SAG convened twice during 2012 to 2013 and developed a strategic, iterative, parallel research approach for beaked whales (primarily involving field work with existing methods) and porpoises (primarily involving laboratory studies with existing methods) that could be implemented to address specific information gaps, if deemed necessary. The SAG's report of their recommended research approach was submitted to the National Marine Fisheries Service in August 2013.

    In their report, the SAG concluded that the available data suggest that the potential for adverse effects to beaked whales and harbor porpoises from exposure to SURTASS LFA sonar appears limited. They also concluded that the potential effects of SURTASS LFA sonar on marine mammal species within these two odontocete taxa would depend largely on the frequencies of the transmissions relative to the species' hearing sensitivity, the species' responsiveness to underwater sounds, and the spatial overlap between SURTASS LFA sonar mission areas and the species' distributions. However, the SAG concluded that a number of research questions should be addressed to verify this conclusion and provided several specific recommendations to address the research questions.


    LOW FREQUENCY SOUND SCIENTIFIC RESEARCH PROGRAM (LFS SRP)

    The goal of the Scientific Research Program was to demonstrate the avoidance reaction during critical biologically important behavior of sensitive species to the low frequency underwater sound produced by the LFA system. If the prevailing theory that a 140 dB received sound level would drive away marine mammals, then LFA probably would not be deployed or would be severely restricted. 

    Testing was conducted in three phases.   The chart shows the location of each phase.  Clicking on the chart will take you to a more detailed explanation of each test phase and the results of the testing.

    Phase I (Sept-Oct 97)
              Species:  Blue and Fin Whales
    Phase II (Jan 98)
              Species: Gray Whales
    Phase III (Feb-Mar 98)
              Species: Humpback Whales
    Scientific Research Program - Phase Map showing Phase I (Southern CA Offshore, West of San Nicolas Is.), Phase II (Central CA Offshore), Phase III (Hawaii Offshore).

    SRP Phase I

    Objectives

    The primary objective of Phase I was to determine whether exposure to low frequency sounds elicited disturbance reactions from feeding blue or fin whales. The goal was to characterize how whale reactions vary to the sounds, depending on: (1) the received level of the sound, (2) changes in the received level, and (3) whether the system was operating at a relatively constant distance or approaching a whale. The chart below shows the test area, located west of San Nicolas Island, off the coast of southern California.
    Map for SRP Phase I, dated 17 September - 13 October 1997, showing Primary Research Area located west of San Nicolas Island, off the coast of southern California.
    SRP Phase I - Video Frame, showing aerial image of phase I test area. (Click on the picture to the left to view a video of Phase I)

    Phase I Research Approach

    • Bottom Bounce
      • Sound refracted downward and reflected upward off of the bottom
      • Simulate sound field that whales could experience from distant source 
    Phase I Bottom-Bounce Approach
    • Direct Path
      • Omni-directional sound field
      • Simulate sound field that whales could experience from an approaching source
    SRP Phase I Direct Path Approach
    Phase I Research Assets
    • Research Vessel Cory Chouest
      • Source Ship
      • Acoustic recordings, especially whale vocalizations
    • Research Vessel Dariabar
      • Independent observation vessel
      • Marine mammal experts observed fin and blue whale behavior 
      • Acoustic recordings, especially whale vocalizations
    • Research Vessel John Martin
      • Surveyed prey fields (whale food)
      • Tagged blue and fin whales with time/depth recorders to assess dive behavior 
    • Aerial Surveys
      • Distribution and density of marine mammals 
    • Pop-Ups
      • Autonomous seafloor acoustic recording units 
    • SOSUS
      • Acoustic recordings from Navy seafloor passive hydrophone arrays 
           
    Phase I Results
    • Full and reduced LFA source power transmissions were used.
    • Highest received levels at animals estimated to be 148-155 dB.
    • In 19 focal animal observations (4 blue whales and 15 fin whales), no overt behavioral responses were observed. Note: A focal animal is an individual animal selected for intensive observation during an experiment.
    • No changes in whale distribution could be related to LFA operations; whale distributions closely tracked the distribution of food.
    • One preliminary analysis of whale sounds detections indicated a slight decrease in whale calling activity during LFA operations, but this was not confirmed by a second analysis.

    SRP Phase II

    Objectives
    • Quantify responses of migrating gray whales to low frequency sound signals.
    • Compare whale responses to different received levels (RL).
    • Determine whether whales respond more strongly to RL, sound gradient, or range to the source.
    • Compare whale avoidance responses to low frequency source in the center of the migration corridor versus in the offshore portion of the migration corridor. 

    SRP Phase II Map showing Gray Whale Migration Corridor, Source Vessel position, Sound Monitoring Vessel position and Observation Site station positions on shore.

    Phase II video frame, showing onshore observers. (Click on the picture to the left to view a video of Phase II)
    Phase II Assets
    For this phase of the Scientific Research Program, a sound source was moored offshore of the central California coast, near Point Buchon.  Shore-based observers tracked whales using methods that provided highly sensitive measures for avoidance responses.  Observers on the playback vessel (100 ft work boat) also carefully monitored marine mammals in order to stop broadcasting in case of worrisome behavioral reactions or if any marine mammals were sighted at close enough range that the sound level to which they were exposed might exceed the maximum planned exposure level (155dB).
    Phase II Assets drawing depicting 100 ft work boat single sound source, Rigid Hull inflatable boat (RHIB), Sound Level Monitoring, and onshore observers.

    Phase II Results
    When the source was moored 1 mile offshore, in the middle of the migration path, whales showed avoidance responses
    • A single source was used to broadcast LFA sounds at source levels up to 200 dB.
    • When the source was moored 1 mile offshore, in the middle of the migration path, whales showed avoidance responses similar to those reported by Malme et al. (1983, 1984).
    When the source was moored 2 miles offshore, responses where much less
    • Whales returned to their migration path within a few kilometers.
    • When the source was moored 2 miles offshore, responses where much less, even when the source level was increased to 200 dB, to achieve the same received level for most whales in the middle of the migration corridor.
    • Offshore whales did not appear to avoid the louder offshore source.

    SRP Phase III

    Acoustic Playback Vessel

    Cory Chouest Drawing
      
    R/V Cory Chouest

    Phase III video frame, showing R/V Cory Chouest
    (Click on the picture above
    to view a video of Phase III)

    Phase III Objectives

    Assess potential effects of LFA signals on behavior, vocalization and movement of humpback whales off the Kona coast.
    Phase III Approach
    • Shipboard visual and acoustic observation.
    • Shore-based visual observation.
    • Controlled exposure of whales to LFA from SURTASS LFA source.
    • SURTASS ship (passive only) available for better localization and additional observations 
    • Additional R/V collects visual, acoustic and sound field data 
    • Applicable mitigation measures employed during all operations

    Hawaiian Islands

    Map of Hawiian Islands

    Phase III Research Area Map Closeup

    Phase III Assets
    For this phase of the SRP, the Research Vessel Cory Chouest operated off the west coast of the big island of Hawaii.  A passive SURTASS ship also participated to listen for whale songs.  Shore-based observers tracked whales. Calibrated hydrophones were deployed from a small vessel to measure received levels (RL), verify the transmission loss (TL) models and improve determination of the sound field to which the whales were exposed.  This vessel also followed individual humpback whales and described in detail their surface behaviors before, during, and after LFA transmissions. Visual and acoustic observers on the playback vessel (R/V Cory Chouest) carefully monitored marine mammals in order to stop broadcasting in case of worrisome behavioral reactions or if any marine mammals were sighted at close enough range that the sound level to which they were exposed might exceed the maximum planned exposure level.
    Phase III Assets: Cory Chouest (Playback Vessel), Rigid Hull Inflatable Boat (RHIB), T-AGOS Ship, Land-Based Observers
    Phase III Summary
    • 33 LFA playback (acoustic transmission) experiments.
    • More than 950 humpback sightings. 
    • 500 hours of passive acoustic data collected.
    • Whale exposure levels of 115 dB to 151 dB. 
    • Variety of responses to playbacks, including temporary cessation of song and apparent temporary avoidance response.
    • Many whales continued to sing and interact with other whales during playbacks.
    • Three aerial surveys conducted as part of separate research project but included Phase III study area during playbacks.

      -Whale distributions and abundances compared with similar survey data from    1993 and 1995.

    Phase III Results
    • Maximum exposure levels were as high as 152 dB.
    • Roughly half of the whales that were observed visually ceased their song during transmissions, but many of these did so while joining a group of whales (when singers usually stop their songs).
    • All singers who interrupted their songs were observed to resume singing within tens of minutes.
    • Analysis of one data set showed that whales increased their song lengths during LFA transmissions, but a second analysis indicated that song length changes were more complicated, and depended on the portion of the song that was overlapped by LFA transmissions.
    • A delayed response to LFA transmissions was observed, in the form of an increase in song length that occurred 1-2 hours after the last transmission.
    • Overall patterns of singer and cow-calf abundance were the same throughout the experiments as they had been during several years of prior study.  

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    | Highlights | Why the United States Needs SURTASS LFA |
    | SURTASS LFA Systems Description | Key Facts | Environmental Impact Analysis |
    | Scientific Research | Preventive Measures | Public Involvement |
    | Frequently Asked Questions | Diver Studies | Terminology |
    |
    Glossary | Files to Download | Contact Us |
    | Home |

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