‘Genoustics’: Combining near-field acoustic records, genetic identity, and photograph records of an individual blue whale off the central Oregon coast

Here we present results of a pilot project to simultaneously collect photographs, acoustic call records, and tissue biopsy sample of a blue whale from the eastern North Pacific, with the goal to assign the individual to a population of origin based on acoustic call records and genetic profile. On 17 October 2018, a pair of blue whales was located ~27 miles off the Oregon coast. Using a small research vessel, we documented the encounter with photographs and collected a tissue biopsy from one of the two whales while their vocalizations were recorded using a drifting hydrophone. We constructed a DNA profile consisting of mitochondrial DNA haplotype, sex, and 15 microsatellite loci. The DNA profile identified the blue whale as male and the assignment test confirmed an eastern North Pacific origin through a comparison to reference databases of blue whales from the North Pacific, South Pacific, eastern tropical Pacific and Southern Ocean. A comparison of the photographs of the two whales to a catalog of blue whale images from the eastern North Pacific showed both whales had previously been sighted on more than one occasion in waters off California between 1994 and 2005. Review of the 68.7-minute drifting hydrophone record detected 5 “A” and 27 “B” type calls, which have been identified as typical eastern North Pacific call types. The maximum call received levels were ~110 dB re μPa
²
-Hz
^-1
estimated using the third harmonic of the B call which had a frequency range of ~40-45 Hz and a high signal to noise ratio (~40 dB). Based on a simple transmission loss estimate, the third harmonic received level suggests a ~7 km distance from the hydrophone to the vocal whale. GPS tracking showed the boat remained in an elliptical area (r~10 km) while circling the pair of whales, consistent with the sampled whale as the call source. Although we cannot confirm the identity of the calling whale, the photo-identification records confirm the two blue whales have previously been sighted in the eastern North Pacific and suggests our acoustic and genetic analysis results are consistent with previous studies showing the ability to link acoustic call types and the whale's sex.