Alessandro Bocconcelli

Underwater components of humpback whale bubble-net feeding behaviour

Summary Humpback whales (Megaptera novaeangliae) employ a unique and complex foraging behaviour — bubble-netting — that involves expelling air underwater to form a vertical cylinder-ring of bubbles around prey. We used digital suction cup tags (DTAGs) that concurrently measure pitch, roll, heading, depth and sound (96 kHz sampling rate), to provide the first depiction of the underwater behaviours in which humpback whales engage during bubble-net feeding. Body mechanics and swim paths were analysed using custom visualization software that animates the underwater track of the whale and quantifies tag sensor values. Bubble production was identified aurally and through spectrographic analysis of tag audio records. We identified two classes of behaviour (upward-spiral; 6 animals, 118 events and double-loop; 3 animals, 182 events) that whales used to create bubble nets. Specifically, we show the actual swim path of the whales (e.g., number of revolutions, turning rate, depth interval of spiral), when and where in the process bubbles were expelled and the pattern of bubble expulsion used by the animals. Relative to other baleanopterids, bubble-netting humpbacks demonstrate increased manoeuvrability probably aided by a unique hydrodynamicly enhanced body form. We identified an approximately 20 m depth or depth interval limit to the use of bubble nets and suggest that this limit is due to the physics of bubble dispersal to which humpback whales have behaviourally adapted. All animals were feeding with at

The seafloor borehole array seismic system (SEABASS) and VLF ambient noise

The Seafloor Borehole Array Seismic System (SEABASS) has been developed to measure the pressure and threedimensional particle velocity of the VLF sound field (2–50 Hz) below the seafloor in the deep ocean. The system consists of four three-component borehole seismometers (with an optional hydrophone). a borehole digitizing unit, and a seafloor control and recording package. The system can be deployed using a wireline re-entry capability from a conventional research vessel in Deep Sea Drilling Project (DSDP) and Ocean Drilling Project (ODP) boreholes. Data from below the seafloor are acquired either onboard the research vessel via coaxial tether or remotely on the seafloor in a self-contained package. If necessary the data module from the seafloor package can be released independently and recovered on the surface. This paper describes the engineering specifications of SEABASS, the tests that were carried out, and preliminary results from an actual deep sea deployment. VLF ambient noise levels beneath the seafloor acquired on the Low Frequency Acoustic-Seismic Experiment (LFASE) are within 20 dB of levels from previous seafloor borehole seismic experiments and from land borehole measurements. The ambient noise observed on LFASE decreases by up to 12 dB in the upper 100 m of the seafloor in a sedimentary environment.

Characterizing Chilean blue whale vocalizations with DTAGs: a test of using tag accelerometers for caller identification

ABSTRACT Vocal behavior of blue whales (Balaenoptera musculus) in the Gulf of Corcovado, Chile, was analysed using both audio and accelerometer data from digital acoustic recording tags (DTAGs). Over the course of three austral summers (2014, 2015 and 2016), seventeen tags were deployed, yielding 124 h of data. We report the occurrence of Southeast Pacific type 2 (SEP2) calls, which exhibit peak frequencies, durations and timing consistent with previous recordings made using towed and moored hydrophones. We also describe tonal downswept (D) calls, which have not been previously described for this population. As being able to accurately assign vocalizations to individual whales is fundamental for studying communication and for estimating population densities from call rates, we further examine the feasibility of using high-resolution DTAG accelerometers to identify low-frequency calls produced by tagged blue whales. We cross-correlated acoustic signals with simultaneous tri-axial accelerometer readings in order to analyse the phase match as well as the amplitude of accelerometer signals associated with low-frequency calls, which provides a quantitative method of determining if a call is associated with a detectable acceleration signal. Our results suggest that vocalizations from nearby individuals are also capable of registering accelerometer signals in the tagged whales DTAG record. We cross-correlate acceleration vectors between calls to explore the possibility of using signature acceleration patterns associated with sounds produced within the tagged whale as a new method of identifying which accelerometer-detectable calls originate from the tagged animal. Summary: Characterization of the Chilean blue whale vocal repertoire and a modified method of using DTAG accelerometers to identify calling blue whales.

Noise impacts on social sound production by foraging humpback whales

The Stellwagen Bank National Marine Sanctuary, located in an urbanized coastal area off the coast of Massachusetts in the United States, serves as an important foraging habitat for North Atlantic humpback whales (Megaptera novaeangliae). During the summer, large numbers of vessels are present in the vicinity of foraging humpback whales. Humpback whales produce a wide variety of low frequency( 12 hours between 2008-2012 showed decreased call rates and increased call frequency during close vessel passages. The response of the lone lactating female in the analyses was opposite of other whales, in that call rates increased ...

Atlantic Long-Term Oceanographic Mooring (ALTOMOOR)

Funding was provided by the Office of Naval Research through Contract Nos. N000-14-94-10346 and N000-14-90-J-1719.

DTAG studies of blue whales (Balaenoptera musculus) in the Gulf of Corcovado, Chile

This investigation set out to obtain data on the ecology, foraging and acoustic behavior of Chilean blue whales (Balaenoptera musculus) in the Gulf of Corcovado, which is an important feeding ground. We deployed 17 suction cup attached sound and orientation recording tags (DTAGs) on blue whales in 2014-16, for a total duration of 124h 08 min. Acoustic data on the tags revealed a variety of different calls. These included SEP2 (Southeast Pacific) song, previously described in this area, as well as other call types not previously described for Chilean blue whales. Downsweep calls similar to those described for other blue whale populations were observed on several tags, as were various other less stereotyped calls. We are currently working on characterizing these call types and also on using the accelerometers to identify calls from the tagged animal. Tag data will prove useful for interpretation of data collected in this area from passive acoustic monitors (PAM), both for species identification and possibly...

Vocal behavior of North Atlantic humpback whales during reunion events on Stellwagen Bank.

Humpback whales on their feeding grounds are typically found in small, ephemeral groups which have been hypothesized to form and separate to maximize foraging efficiency, but little is known about the functional mechanisms by which these groups change their composition. In this study, we test the hypothesis that specific vocalization types are associated with events where two or more individual humpback whales join to form a cohesive group on their summer feeding grounds. In the summer of 2008, 11 Dtags (a combined acoustic and movement recording tag) were attached to individual humpback whales on their feeding grounds in the Stellwagen Bank National Marine Sanctuary. Behavioral observations were collected from tagged animals at the surface and the timing of join events were recorded. Calls from the tagged whale and nearby associates were identified and analyzed to test for call rate changes between 10 min periods around joining events and 10 min control periods. Additional analyses included call type usa...

The South Atlantic Bight monitoring program

An interdisciplinary monitoring and research program focused on the coastal ocean of the South Atlantic Bight has been implemented by the Center for Marine Science at the University of North Carolina at Wilmington. This program monitors and assesses the physical, biological and chemical aspects of the coastal ocean, including the effects of ocean physics on both the marine environment and major marine resources on relevant time scales. The field sampling program began in the summer of 1999, focusing on the portion of the South Atlantic Bight between New River in Onslow County and Little River at the North/South Carolina border. The program is a mix of scheduled research cruises, continuous monitoring at fixed stations, and quick-response cruises to study special events (hurricanes, floods, winter storms). So far a fully equipped bottom mounted monitoring station has been installed, and scheduled monitoring cruises and a quick response effort for Hurricane Floyd have been completed.

Marine science at the University of North Carolina at Wilmington

The Center for Marine Science Research at the University of North Carolina at Wilmington is dedicated to providing an environment that fosters a multidisciplinary approach to questions in basic marine research. The mission of the center is to promote basic scientific and applied research in the fields of oceanography, marine mammal biology, coastal and wetland studies, marine geology, marine biomedical and environmental physiology, and marine biotechnology and aquaculture. The Center fosters research programs of the highest quality and thereby enhances the educational experience in marine science provided by the University of North Carolina at Wilmington for both undergraduate and graduate students in marine science. A new Center for Marine Science Research is under construction on the Intracoastal Waterway. The planned building will have 4,372 net square meters (47,000 square feet) of marine education and research space. The gross area including the saltwater facility is 6,511 square meters (70,000 square feet). A 274 meter (900 foot) pier with floating docks is already in place and can accommodate a large research vessel (20 to 25 meters) and several small ones. The construction project is expected to be completed by December of 1998. The new Center will host several state agencies and will provide space and facilities for visiting scientists. Support facilities will include: an 18 meter research vessel two 9 meter research vessels, eight smaller vessels (ranging from 4 to 6 meters), instrument shop, diving locker, engineering/logistic support personnel and salt water plant with unfiltered, filtered and treated sea water. The Center will act as a focal point for marine science research and education programs on the southeast Atlantic coast.

Seafloor borehole array seismic system (SEABASS)

This work was carried out under JHU Contract # 602809-0 and under ONR contracts #N00014-89-C-0018, #N00014-89-J-1012, and #N00014-90-C-0098.