CFER Project Title: Passive Acoustic Applications in Marine Fisheries
PIs: Clifford Goudey, MIT Sea Grant, Rodney Rountree, UMass/Dartmouth and Tony Hawkins, University of Aberdeen, King's College, UK

Project Summary
Research Protocol Outline

 

Prelimnary Project Findings

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Research Summary
Our preliminary findings indicate that the haddock aggregations were present soon after our deployments began on Jefferies Ledge and the onset of vocalizations seems to coincide with local fisherman’s knowledge of haddock spawning. Figure 3 is an example of series of haddock calls recorded on Jefferies Ledge at 1:45 pm on 8 May, 2003:



Figure 3. Waveform of haddock calls on Jefferies Ledge (23 sec.).
Date: 5/8/03 Time: 1:45pm ID: Haddock calls, Jeffries Ledge

This is a clean, easily identified signal accompanied by relatively low levels ambient sea-state noise. Earlier in that same deployment we were surprised to see the 15-min. recording shown in Figure 4. This reveals the acoustic environment is being dominated by sound that arrives at exactly 18-seconf intervals. After some investigation we learned that Marathon Oil Corporation had begun seismic tests in a location known as the Gully, southwest of Sable Island east of Nova Scotia. In spite of these sounds, we are able to identify haddock calls, which can be seen as lower-amplitude signals in between the air gun blasts. Such pollution from oil and gas activity can persist for hours and days depending on the schedule of the survey ships and the acoustic conditions of the waters between the source and our listening station.

Figure 4. A 15-minute recording from Jefferies Ledge showing seismic testing off Sable Island.
Date: 5/8/03 Time: prior to 1:45pm ID: seismic testing, Jeffries Ledge

Figure 5 shown another series of haddock calls recorded on May 9 that occur along with the 18-second seismic blasts. So far we are unable to conclude whether this level of persistent anthropogenic noise has an effect on fish vocalization rates. Two other examples of haddock calls are presented in Figures 6 and 7. The latter is likely the latter stages of spawning activity during which courtship vocalizations grow in intensity and repetition rate.

Figure 5. A characteristic pre-spawning haddock call mingled with seismic blast (41 sec.)
Date: 5/9/03 Time: unknown ID:haddock calls, Jeffries Ledge

Figure 6. May 9, Jefferies Ledge, 1:20 pm, haddock calls
Date: 5/9/03 Time: 1:20pm ID: haddock calls, Jeffries Ledge
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Figure 7. May 9, Jefferies Ledge, 1:47 pm, spawning haddock calls (90 seconds)
Date: 5/9/03 Time: 1:47pm ID: spawning haddock calls, Jeffries Ledge
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Whale calls are also common on Jefferies Ledge and are easily detectable. Figure 8 is a three-call sequence, probably representing more than one whale.

Figure 8. Three whale calls recorded on Jefferies Ledge at 6:00 am on 11 May (28 sec.)
Date: 5/11/03 Time: 6:00am ID: Whale calls, Jeffries Ledge

Based on cursory viewing of waveforms and manual comparisons of the sounds with know laboratory and field recordings, we have found that most of the haddock acoustic activity occurs late afternoon and evening. A shorter waveform display of a single whale call is shown in Figure 9, showing the characteristic 45 Hz. of a fin whale.

Figure 9. Waveform of a fin whale recorded on Jefferies Ledge at 2:00 pm on 8 May (1.4 sec.)
Date: 5/8/03 Time:2:00pm ID: Whale calls, Jeffries Ledge

There are many sounds that require speculation as to their source. Figure 10 is an example recorded at 4:00 am on 10 June 12 miles to the east of West Cod ledge of Portland. This record is one of many in a sequence that go on for over 4 hours.



Figure 10. A 15-min. record of repeating unknown sounds east of West Cod Ledge.
Date: 6/10/03 Time 4:00am ID: unknown sounds, 12miles E of West Cod ledge of Portland.

One of the signals is expanded in Figure 11 and some who have listened to it suspect these might come from whales bubble feeding with the open-mouthed breach at the end.



Figure 11. An expansion of a signal from Figure 8 (39 sec.)
Date: 5/11/03 Time: 6:00am ID: Whale calls, Jeffries Ledge

Another example of an unknown sound was recorded on 22 June 3 miles to the northwest of the above location at 9pm. These differ in some respects to those shown in Figure 10 and they endure for nearly three hours. One possible explanation is the hauling of lobster gear . However, the late evening time suggests that the activity might be clandestine. That same night we recorded two unusual sounds that sound like rifle shots and they are shown in Figure 13.

Figure 12. Another 15-min. record of repeating sounds off Portland, possibly night lobstering.
Date: 6/22/03 Time:9:00pm ID:unknown sound, NW of West Cod Ledge, Portland, Maine


Figure 13. Two distinct signals that sound like rifle shots – 22 June, 7:25 pm (0.6 sec.
Date: 6/22/03 Time: 7:25pm ID: possible gun shots


In summary, our recording to date have demonstrated what we had hoped, that our listening stations can detect spawning vocalizations.