Acoustic tracking of sperm whales in the Gulf of Alaska using a two-element vertical array and tags

Abstract

Between 15 and 17 August 2010, a simple two-element vertical array was deployed off the continental slope of Southeast Alaska in 1200 m water depth. The array was attached to a vertical buoy line used to mark each end of a longline fishing set, at 300 m depth, close to the sound-speed minimum of the deep-water profile. The buoy line also served as a depredation decoy, attracting seven sperm whales to the area. One animal was tagged with both a LIMPET dive depth-transmitting satellite and bioacoustic "B-probe" tag. Both tag datasets were used as an independent check of various passive acoustic schemes for tracking the whale in depth and range, which exploited the elevation angles and relative arrival times of multiple ray paths recorded on the array. Analytical tracking formulas were viable up to 2 km range, but only numerical propagation models yielded accurate locations up to at least 35 km range at Beaufort sea state 3. Neither localization approach required knowledge of the local bottom bathymetry. The tracking system was successfully used to estimate the source level of an individual sperm whale's "clicks" and "creaks" and predict the maximum detection range of the signals as a function of sea state.

Review of Underwater and In-Air Sounds Emitted by Australian and Antarctic Marine Mammals

“…Sperm whales have been recorded off the US east coast [324][325][326][327][328], off Nova Scotia [329,330], around the Bahamas [331][332][333], around Bermuda [334], in the Caribbean [335][336][337][338][339], in the Gulf of Mexico [340][341][342][343], in Alaska [344][345][346][347][348], in the northeast Pacific [349], off Japan [350,351] around Hawaii [352], at the Galapagos Islands [173,353,354], at the Azores [355], off Scotland [356], off Norway [357][358][359][360][361], in the Mediterranean [362][363][364][365][366], in the South Pacific [367], in New Zealand [368][369]<...>…”

A multi-hypothesis tracker for clicking whales

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Beaked whales are particularly difficult to track acoustically due to the highly directional nature of their clicks. 7 As a result, little is known about their behavior at depth.…”

“…The parent track is kept as well with a null association in order to cover the possibility that no valid associations exist for some tracks. Tracks with associations were updated according to the measurement update relations (11), (12), (13), and (14).…”

Using a coherent hydrophone array for observing sperm whale range, classification, and shallow-water dive profiles

“…Our analysis of sperm whale clicks is therefore limited to the low-frequency component of the click signals in the several hundred hertz to a couple of kilohertz range that is more omnidirectional (Mathias et al, 2013;Tiemann et al, 2006;Zimmer et al, 2004) and suffer less transmission loss. In contrast, the sampling frequencies of acoustic systems in previous sperm whale studies were significantly higher, by at least a factor of three (Mathias et al, 2013;Tiemann et al, 2006) to over ten times that used in this study to provide a more complete coverage of the bandwidth of the sperm whale click that can extend to 30 kHz (Madsen et al, 2002a;Mathias et al, 2012;Teloni, 2005;Thode, 2004;Watwood et al, 2006;Zimmer et al, 2004).…”

“…Other approaches for localizing sperm whales include (a) hyperbolic ranging with a small network of single hydrophones (Baggenstoss, 2011;Tiemann and Porter, 2003;Watkins and Schevill, 1972) and (b) time-delay measurement of click reflections from ocean boundaries acquired with a single hydrophone or a sparse array of hydrophones (Mathias et al, 2013;Mathias et al, 2012;Nosal and Frazer, 2006;Skarsoulis and Kalogerakis, 2006;Thode, 2004;Tiemann et al, 2006;Wahlberg, 2002). Here we utilize time difference of arrivals of the sperm whale direct and multiple bottom and surface reflected click [multiple-reflection based time difference of arrival (MR-TDA)] signals after beamforming to estimate the depth and hence the dive profile of a sperm whale in shallow waters of the Gulf of Maine with 160 m water-column depth.…”