Autonmous Real-time Marine Mammal Detections

Woods Hole Oceanographic Institution


Outer Fall, Gulf of Maine, Fall 2012


Platforms

Slocum glider we08 (deployed Nov 12, 2012, recovered Dec 4, 2012)

Slocum glider we10 (deployed Nov 12, 2012, recovered Dec 4, 2012)


Study objectives

On November 12, 2012, we deployed two gliders in the Outer Fall region of the central Gulf of Maine to study the calling behavior and prey species of baleen whales. This region is poorly studied because whales occur here during the late fall and winter when the weather is poor and the area is difficult to access by ship. The gliders were equipped with DMON/LFDCS instruments to detect, classify, and report baleen whale calls in near realtime so that we could map the distribution of whales in the area. We used this distribution information to quickly locate whales during a short cruise to the area aboard the R/V Endeavor (November 28 to December 6). The goal of the cruise was to conduct zooplankton sampling to determine the primary prey species of the whales, and to examine the relationship between diel vertical migration of these prey and the diel periodicity in calling behavior of the whales. The cruise found fin, humpback, and right whales in the area, and successfully recovered the gliders on December 4. This was the first application of realtime detection, classification, and reporting of low-frequency baleen whale calls from autonomous underwater vehicles.

Principal Investigators: Mark Baumgartner and Dave Fratantoni (Woods Hole Oceanographic Institution)


Study chronology

Nov 12

Two gliders (we08 and we10) were deployed today in the Outer Fall region west of Jordan Basin in the central Gulf of Maine. The deployment was conducted from the University of New Hampshire's R/V Gulf Challenger by Ben Hodges and Nick Woods of the WHOI Autonomous Systems Lab. Both gliders are equipped with a DMON/LFDCS instrument as well as sensors to measure temperature, conductivity, pressure, optical backscatter, and chlorophyll fluorescence. Glider we08 is also equipped with a 1-MHz acoustic doppler current profiler which we are using as a crude echosounder. The gliders were deployed in the late morning.

Nov 13

Glider we10 is working as expected; however, glider we08 is reporting evidence of a small leak. The glider is operational, but Dave will be conservative and have it do shallow dives until the problem can be better assessed.

Nov 14

Glider we08 detected whale calling for the first time today! Individual calls were classified as 20-Hz fin whale calls (call type 4) using quadratic discriminant function analysis aboard the DMON/LFDCS, and the reported pitch tracks revealed a pattern of repetitive calls that are diagnostic of the species.

Nov 15

After initial tests were completed, both gliders were provided survey missions today. Glider we08 will occupy a station near the middle of our operational area and remain there in pseudo-mooring (station-keeping) mode. It is clear there has been a small leak in we08, but the glider is stable and can remain on station doing dives to 50 m. Dave will increase the dive depth to 75 m later today. Glider we10 will do a spatial survey throughout the study area to map the distribution of whales prior to our arrival on the R/V Endeavor on Thursday, November 29. Glider we10 is diving from surface to bottom, and is following transects from southwest to northeast oriented parallel to the edges of the study area.

Nov 17

Glider we10 detected right whales in the northeastern part of the study area today during the afternoon and evening. The pitch tracks indicated isolated upcalls with occasional moans and no evidence of humpback whale call interference.

Nov 18

Glider we10 detected humpback whale singing today; pitch tracks (example 1, example 2) showed patterned calls characteristic of the species. Glider we08 is reporting a more serious leak condition, so it will remain on station diving to 50 m. We plan to recover this glider during the R/V Endeavor cruise next week.

Nov 19

NOAA NEFSC aerial survey is planned for the Outer Fall region today. Provided recent right whale detection positions to Pete Duley (on 11/17 near 68.328W, 43.510N, and on early morning of 11/19 near 68.607W, 43.254N).

Nov 20

The NOAA NEFSC aerial survey team reported seeing fin whales, but no right or humpback whales in our study area yesterday. Disparities between visual sightings and acoustic detections are well known (see Clark et al. 2010), but a lack of right and humpback whale sightings in the area suggests that abundance of these species may be low.

Nov 21

Glider we10 found two discrete areas of fin whale calling, but so far the current southwest-to-northeast transect has been fairly quiet compared to the eastern transect completed earlier this week.

Nov 22

Happy Thanksgiving! Glider we10 reported hearing loud humpback whale singing last night and early this morning which was captured beautifully in the transmitted pitch tracks (example 1, example 2, example 3).

Nov 23

Glider we10 detected right whale upcalls overnight near position 43.408N, 68.445W. The pitch tracks (example 1, example 2) indicate little humpback whale calling. This glider is nearing the area where it detected right whales nearly a week ago, so it will be interesting to see if it detects right whales in this general area again.

Nov 24

Glider we08 detected right whale upcalls late last evening near position 43.317N, 68.645W. The pitch tracks (example 1, example 2, example 3) indicate faint humpback whale calling in the area.

Nov 25

Glider we10 detected fin whales late yesterday afternoon, and glider we08 heard fin whale calls overnight. The northeast-to-southwest transect conducted by we10 today yielded very few detections of humpback whales, and no detections of right whales. Glider we10 will transit to the southern corner of our study area and will survey to the northeast from there.

Nov 26

Fin whales were detected on glider we10 overnight, but no right, sei, or humpback calls have been detected at the southern end of our study area so far. More fin whale calling was detected last night by glider we08.

Nov 27

A few faint right whale upcalls were detected by glider we08 last night (example 1, example 2). Glider we10 has reached the southernmost region of our study area and has detected no whales there at all.

Nov 28

The R/V Endeavor left the dock today with 7 scientists aboard to conduct oceanographic and zooplankton sampling in the Outer Fall region. We will use the glider detection data collected over the past 2 weeks to plan our operations. Weather is not ideal for finding marine mammals, but this was not unexpected. Conducted equipment tests in Cape Cod Bay during our transit, and proceeded overnight to the Outer Fall.

Glider we08 is detecting numerous fin whale calls, and during the afternoon, a few sporadic right whale upcalls. Glider we10 is detecting fin whale calls along the most southeastern part of the survey area.

Nov 29

Rendezvoused with we08 aboard the Endeavor this morning, but sighting conditions are poor: 20-25 knot winds and seas are around 8 feet. Finding a whale anywhere beyond a few hundred meters of the ship is exceedingly unlikely, and identifying the species in this swell is even less likely. Conducted instrument casts from the ship near glider we08 and then proceeded to glider we10's position in the afternoon to do the same. Upon completion, we started to steam back toward we08 in the evening, but the weather was too rough to continue on that heading (the deck was regularly awash, deck operations were halted, and the aft doors were secured for the night).

Call detections are extremely scarce at we08 today, but fin whale and some humpback whale calling was detected on we10 in the northeastern corner of the survey area (example).

Nov 30

Sighting conditions are marginally better today on the Endeavor: 20-25 knot winds and seas around 7 feet. Starting at glider we08's position, we steamed north-northeast and found one (possibly 2) right whales after only a little more than 3 hours of searching. We followed one of the whales for several hours as it traveled to the southwest (directly toward and eventually past glider we08) and we conducted oceanographic and zooplankton sampling along the way.

Unlike yesterday, glider we08 detected many calls today, including those of fin, humpback, and right whales. Interestingly, there are several unclassified groupings of calls that appear to be pitch-tracked gunshot calls (example), a distinctive call made by male right whales that is not in the DMON/LFDCS call library. Will need to verify this once the gliders are recovered and we can access the recorded audio.

We sent glider we10 outside (to the north) of the study area today to see if a pocket of right whales were lurking just outside of our survey box. Unlike yesterday, we10 heard almost no fin whale calling, but it did detect both humpback and right whale calls. While some right whale calls were isolated from those of humpbacks, the co-occurrence of the two makes these right whale calls a bit suspicious.

Dec 1

Weather conditions are ideal today; winds around 10 knots, no swell, and small wind waves. Surveyed from the Endeavor around glider we08, and toward the end of the day we surveyed close to glider we10. Found fin, humpback, and sei whales today, as well as a single right whale. Whale abundance is quite low; all but one of the large whale sightings consist of single animals.

Both gliders we08 and we10 detected right, humpback, and fin whale calls today (glider we10 was in the northern end of the survey area).

Dec 2

The weather deteriorated overnight and sighting conditions from the Endeavor are again very poor: 25-30 knot winds with gusts well into the 30's, seas building to around 8-10 feet, periods of pelting rain (or sleet), and some fog. We maintained a full observer rotation and surveyed from dawn until dusk, but only saw the blow of a single unidentified whale in the same location that we10 detected right whale calls yesterday. Began conducting instrument casts at stations along our survey lines to characterize oceanographic conditions and zooplankton distribution.

Glider we08 detected fin and humpback whale calls again today. Although no right whale upcalls were detected, the same "stacked" call groupings suggestive of right whale gunshots were detected in the pitch tracks (example). Glider we10 surveyed the southwestern portion of the survey area, but very few calls were detected, and most of these were humpback calls.

Dec 3

Although the winds and seas calmed a bit this morning, winds picked up again in the afternoon to 25-30 knots and conditions were eventually as bad as yesterday. Only a few whales were seen from the Endeavor today: a few fin whales and one unidentified large whale (most likely not a right whale). Continued to conduct instrument casts at stations along our survey lines.

Dave instructed gliders we08 and we10 to rendezvous with one another in the southwestern part of the study area for recovery tomorrow. Glider we08 detected fin whales today, and more instances of the stacked call groupings suggestive of right whale gunshots were apparent in the pitch tracks today (example). Glider we10 detected only a few fin whale calls today.

Dec 4

Very calm conditions this morning. After conducting an instrument cast near the the glider pickup position, we located the gliders easily (they were within a few hundred meters of one another), deployed our small boat, and recovered the gliders. It is wonderful to have them back safe! After surveying for a short while, we found several right whales (as many as 9) dispersed over several miles. We attempted to attach a short-term archival tag to one to study its foraging behavior, but the whales were uncooperative and the weather deteriorated in the early afternoon. The New England Aquarium team took the rest of the day and photographed the whales in the area from the Endeavor to individually identify them (see what they found at the NEAq Right Whale Research Blog). After nightfall, we established a station in the area and sampled with both our instruments as well as with zooplankton nets through the night and during the next morning. Weather conditions overnight deteriorated further until winds were sustained at 25-30 knots and seas built to around 8 feet.

Dec 5

Rough conditions this morning forced us to cancel our morning zooplankton sampling with the large net system we brought along. We ended our hourly instrument casts at 9 am, and began steaming toward Narragansett, Rhode Island, home port of the Endeavor. Seas were 8-10 feet all day, so it was a sloppy ride, but its nice to be heading home.

Acknowledgements

The DMON instrument was developed by Mark Johnson and Tom Hurst at WHOI. Mark Johnson was responsible for developing the application programming interface (API) for the DMON, and coded the original DMON implementation of the pitch tracking algorithm described in Baumgartner and Mussoline (2011). The gliders were expertly deployed by Ben Hodges and Nick Woods (WHOI). At sea assistance provided by the captains and crew of the R/V Gulf Challenger and R/V Endeavor, as well as the following Endeavor cruise participants - from WHOI: Nadine Lysiak, Desray Reeb, Morgan Rubanow, and Chris Tremblay; from the New England Aquarium: Moira Brown, Marianna Hagbloom, and Tracy Montgomery. This work is the product of a long and close collaboration between WHOI and the NOAA Northeast Fisheries Science Center's Passive Acoustic Research Group (leader: Sofie Van Parijs). Support for the development, integration, and testing of the glider DMON/LFDCS was provided by the Office of Naval Research and the NOAA National Marine Fisheries Service Advanced Sampling Technologies Working Group (NOAA funding provided through the Cooperative Institute for the North Atlantic Region).


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