Research reveals bottom feeding techniques of tagged humpback whales in Stellwagen Bank National Marine Sanctuary

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Anne Smrcina, 781-545-8026 x204 Research reveals bottom feeding techniques of tagged humpback whales in Stellwagen Bank National Marine Sanctuary

New NOAA-led research on tagged humpback whales in Stellwagen Bank National Marine Sanctuary reveals a variety of previously unknown feeding techniques along the seafloor. Rather than a single bottom feeding behavior, the whales show three distinct feeding approaches: simple side-rolls, side-roll inversions, and repetitive scooping.

A recently published paper, in the journal Marine Mammal Science, indicates that bottom side-roll techniques are common in Stellwagen Bank National Marine Sanctuary and the Great South Channel study area, a deep-water passage between Nantucket, Mass. and Georges Bank-further southeast.

The study further states that the observed feeding behavior also leads to vulnerability to entanglement in bottom set fishing gear, an issue which is a major mortality factor for the species. This finding reaffirms a NOAA Fisheries regulation that mandates the use of sinking line between fishing traps used in the lobster fishery as a way of reducing entanglements.

The new findings follow earlier NOAA-led studies detailing so-called "bubble net" feeding behaviors near and at the surface. Bubble net feeding is a behavior in which humpback whales corral and contain fish into a small area by trapping them in nets of air bubbles so they can more efficiently scoop them up in their large filter-feeding mouths.The behaviors are used by individual animals and as part of coordinated feeding behaviors involving two or more animals.

"Tagging technology is allowing us to observe whales underwater, much as land-based biologists study animal subjects in their specific environments," said David Wiley, sanctuary research coordinator and a co-author on the paper. "The data have allowed us to detect new feeding techniques as well as nuances in those behaviors. We have determined that bottom feeding is a much more commonly used technique than the more well known bubble net behaviors."

Bottom side-rolling feeding was previously hypothesized from observations of scars on the jaws of humpback whales and from earlier tagging projects. In the recent studies, researchers showed that this behavior happens for extensive periods of time at or near the seafloor, that it occurs in the presence of concentrations of sand lance (a preferred prey fish), and that the behavior is accompanied by the expansion of the animal's ventral (throat) pleats.

Information was collected through the use of DTAGs (synchronous motion and acoustic recording tags) and Crittercam™, National Geographic Society's underwater video and audio recording system.

Humpback whale with a scrape on its rostrum. Scientists say injuries such as this one are sometimes a result from bottom-feeding. (Credit: NOAA/Stellwagen Bank National Marine Sanctuary )"By visualizing the data with TrackPlot, we can actually see how the whale moves underwater and this enables us to discover different kinds of foraging behaviors," said lead author Colin Ware of the University of New Hampshire's Center for Coastal and Ocean Mapping. TrackPlot is a custom software tool for DTAG data that produces a ribbon-like image in three dimensions. "With these 3-D visualizations, we can follow the path of the whale from surface to seafloor along with all of the pitch, roll and heading changes while underway. By adding Crittercam video, we now get a more complete understanding of these various bottom feeding techniques," Ware said.

A side-roll is defined as a roll of between 45 and 135 degrees from a normal orientation along the seafloor - the most common version uses a 90 degree roll with a downward head pitch of about 30 degrees, which matches favorably with earlier speculative sketches of bottom feeding. A side-roll inversion involves rolls that continue past the 135 degree orientation position. One humpback used a technique that employed a repetitive sequence of moves approximately every 20 feet during which the animal rolled from a 90 degree position to an inverted position, with some 10 to 17 of these "scoops" per dive.

The whale's body orientation during bottom side-roll feeding is depicted in this computer-generated image. (Credit: Colin Ware, University of New Hampshire Center for Coastal and Ocean Mapping)Sand lance, also known as sand eels, tend to burrow into the sandy sediments at night or form nighttime horizontal schools close to the seafloor. In addition, Crittercam footage indicates that sand lance can form dense mats along the seabed during the day. The side roll feeding technique with extended pleats emphasizes width rather than height, resulting in more efficient feeding when encountering prey at or near the seafloor. Coordinated feeding may also help cluster prey or simply ensure that it does not escape. Crittercam footage also showed for the first time a head-to-head orientation for two animals that were side-rolling at the seafloor.

While this humpback bottom feeding behavior occurs at relatively slow speeds, it does involve the expansion of ventral pleats, which was once thought to require high speeds, as in lunging. The researchers theorize that humpback side rolls may be similar to the feeding technique of gray whales in the Pacific. The three types of bottom feeding techniques may be due to different prey distributions or may just reflect individual preferences between whales. In this 3D computer visualization, the roller coaster-like movement of a tagged humpback whale in Stellwagen Bank National Marine Sanctuary is captured over a nearly two-hour period. The whale traveled at depths ranging from 30 to 150 feet deep. The red and blue triangles along the ribbon show the whale's powerful fluke, or tail fin strokes that propel it through the water. The yellow sections along the ribbons indicate where bottom side-roll feeding occurs. (Credit: Colin Ware, University of New Hampshire Center for Coastal and Ocean Mapping)

Funding and additional support came from NOAA Office of National Marine Sanctuaries, NOAA Office of Marine and Aviation Operations, NOAA-University of New Hampshire Center for Coastal and Ocean Mapping, Office of Naval Research, National Oceanographic Partnership Program, Duke University Marine Laboratory, National Geographic Society, International Fund for Animal Welfare, Pacific Life Foundation and the Volgenau Foundation.

Designated in 1992, Stellwagen Bank National Marine Sanctuary encompasses 842 square miles of ocean, stretching between Cape Ann and Cape Cod offshore of Massachusetts. Renowned for its scenic beauty and remarkable productivity, the sanctuary supports a rich diversity of marine life including endangered great whales, seabirds, more than 60 species of fishes and hundreds of marine invertebrates.

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Application to import 18 beluga whales for public display denied

August 6, 2013

Following a number of public engagement efforts, NOAA Fisheries today announced it is denying the Georgia Aquarium’s request for a permit to import 18 beluga whales from Russia for public display in the United States. NOAA Fisheries based the decision on requirements of the Marine Mammal Protection Act (MMPA).

The MMPA allows marine mammals to be removed from the wild or imported for the purpose of public display, and provides a process for issuing permits. This is the first application for a permit to import recently caught wild marine mammals in more than 20 years.

“The Georgia Aquarium clearly worked hard to follow the required process and submit a thorough application, and we appreciate their patience and cooperation as we carefully considered this case,” said Sam Rauch, acting assistant NOAA administrator for NOAA Fisheries. “However, under the strict criteria of the law, we were unable to determine if the import of these belugas, combined with the active capture operation in Russia and other human activities, would have an adverse impact on this stock of wild beluga whales.”

After careful review, NOAA Fisheries concluded that the application did not meet several of the MMPA permit criteria. NOAA Fisheries denied the permit application because:

NOAA Fisheries is unable to determine whether or not the proposed importation, by itself or in combination with other activities, would have a significant adverse impact on the Sakhalin-Amur beluga whale stock, the population that these whales are taken from; NOAA Fisheries determined that the requested import will likely result in the taking of marine mammals beyond those authorized by the permit; NOAA Fisheries determined that five of the beluga whales proposed for import, estimated to be approximately 1½ years old at the time of capture, were potentially still nursing and not yet independent.  

Beluga whale pod in the Chukchi sea on July 1st 2008.
Marine Mammal Permit: 14245

High resolution (Credit: NOAA)

The Aquarium sought to import the whales from Utrish Marine Mammal Research Station on Russia’s Black Sea Coast for public display at its own facility in Atlanta and at partner facilities, including SeaWorld of Florida, SeaWorld of Texas, SeaWorld of California and Shedd Aquarium in Chicago.

The whales were captured from Russia’s Sea of Okhotsk between 2006 and 2011. There is little reliable scientific information about the size and population trend of the Sakhalin-Amur stock of belugas, and the impact on the stock of other human activities, such as hunting and fishing, is unknown.

NOAA Fisheries held a public hearing on the proposed beluga whale importation on October 12, 2012. The 60-day public comment period closed Oct. 29, 2012, with NOAA Fisheries receiving approximately 9,000 comments.

Beluga whales are social animals that typically migrate, hunt and interact together in groups of ten to several hundred in the arctic and subarctic waters of Russia, Greenland and North America. Beluga whales face a number of threats including ship strikes, pollution, habitat destruction and entanglement in fishing gear.

For more information, including the decision memo, are available online.

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