SURTASS LFA

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


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.

	(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

Direct Path Omni-directional sound field Simulate sound field that whales could experience from an approaching source

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.

	(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 Results
	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).
	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 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
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 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.