Volume 19, Number 4
October 2003
TWO TYPES OF BLUE WHALE CALLS RECORDED IN THE GULF OF ALASKA. Kathleen M.
Stafford, pages 682-693.
At one time blue whales were found throughout the Gulf of Alaska, however,
none have been sighted there in post-whaling era surveys. To determine if
blue whales (Balaenoptera musculus) might now occur in the Gulf of Alaska,
an array of hydrophones was deployed there in October 1999. Data were
retrieved in May 2000 and in June 2001. Spectrograms from a random
subsample comprising 15% of the 63,000 h of data were visually examined
for blue whale calls. Call types attributed to both northeastern and
northwestern Pacific blue whales were recorded. Both of these call types
were recorded seasonally from the initial deployment date in October 1999
through the third week of December 1999 and then from July 2000 through
mid-December 2000. Both call types were regularly recorded on the same
hydrophone at the same time indicating clear temporal and spatial overlap
of the animals producing these calls. Two blue whale call types were
recorded in the Gulf of Alaska suggesting that perhaps two stocks use this
area. The northeastern call type has now been documented from the equator
up to at least 55N in the eastern North Pacific.
LOCALIZATION OF NORTH ATLANTIC RIGHT WHALE SOUNDS IN THE BAY OF FUNDY
USING A SONOBUOY ARRAY. Marjo H. Laurinolli, Alex E. Hay, Francine
Desharnais, and Christopher T. Taggart, pages 708-723.
A free-drifting 14-sonobuoy array was used to localize North Atlantic
right whales (Eubalaena glacialis) in the Grand Manan Basin area of the
Bay of Fundy. This area is a primary summer/autumn right whale habitat and
overlaps an international shipping lane. The three-hour deployment on a
single day provided two-dimensional localization of 94 right whale sounds
based on arrival time differences determined from spectrogram
cross-correlation analysis. The sounds were of two distinct types: tonal
and gunshot. Maximum detection distances were about 30 km for both types
of sound. The mean RMS location error was 1.8 km for tonal-type sounds and
2.5 km for gunshot-type sounds. The average RMS error was 20% of the
average distance from the receiving hydrophones, the primary source of
error being uncertainty in the sonobuoy positions.
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