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Munger, LM, Wiggins SM, Moore SE, Hildebrand JA.  2008.  North Pacific right whale (Eubalaena japonica) seasonal and diel calling patterns from long-term acoustic recordings in the southeastern Bering Sea, 2000-2006. Marine Mammal Science. 24:795-814.   10.1111/j.1748-7692.2008.00219.x   AbstractWebsite

We assessed North Pacific right whale (Eubalaena japonica) seasonal and daily calling patterns in the southeastern Bering Sea (SEBS) using long-term hydrophone recordings from October 2000 through January 2006. We detected right whale calls on the SEBS middle shelf (< 100 m depth) as early as May, intermittently throughout summer and fall, and as late as December. Calls also were detected on one day in June 2005 on the SEBS slope (> 1,000 m), but were not detected near Kodiak Island from April to August 2003. In months with calls, detections occurred on more days in July-October (>= 6 d/mo), than from May to June or November to December (<= 3 d/mo). Calls were clustered in time and were usually detected on 1-3 consecutive days with a median interval of 6.5 d for calls > 1 d apart. Hourly calling rates were significantly higher at night than during the day. These data indicate that right whales occur in the SEBS later in the year than previously known, intermittently pass through the middle-shelf study region, and usually remain there no longer than a few days. Right whale habitat use in the SEBS may intensify in mid-summer through early fall based on higher monthly and daily call detection rates.

Munger, LM, Wiggins SM, Hildebrand JA.  2011.  North Pacific right whale up-call source levels and propagation distance on the southeastern Bering Sea shelf. Journal of the Acoustical Society of America. 129:4047-54.   10.1121/1.3557060   AbstractWebsite

Call source levels, transmission loss, and ambient noise levels were estimated for North Pacific right whale (Eubalaena japonica) up-calls recorded in the southeastern Bering Sea in autumn of 2000 and 2001. Distances to calling animals, needed to estimate source levels, were based on two independent techniques: (1) arrival-time differences on three or more hydrophones and (2) shallow-water dispersion of normal modes on a single receiver. Average root-mean-square (rms) call source levels estimated by the two techniques were 178 and 176 dB re 1 muPa at 1 m, respectively, over the up-call frequency band, which was determined per call and averaged 90 to 170 Hz. Peak-to-peak source levels were 14 to 22 dB greater than rms levels. Transmission loss was approximately 15 *log(10)(range), intermediate between cylindrical and spherical spreading. Ambient ocean noise within the up-call band varied from 72 to 91 dB re 1 muPa(2)/Hz. Under average noise conditions, call spectrograms were detectable for whales at distances up to 100 km, but propagation and detection distance may vary depending on environmental parameters and anthropogenic noise. Obtaining distances to animals and acoustic detection range is a step toward using long-term passive acoustic recordings to estimate abundance for this critically endangered whale population.

Širović, A, Johnson SC, Roche LK, Varga LM, Wiggins SM, Hildebrand JA.  2014.  North Pacific right whales (Eubalaena japonica) recorded in the northeastern Pacific Ocean in 2013. Marine Mammal Science. :n/a-n/a.   10.1111/mms.12189   AbstractWebsite