|Marine Mammal Acoustic Operations Summary
CalCOFI 1202, R/V New Horizon, Chief Scientist: David Wolgast
January 27th – February 13th, 2012
Marine Physical Laboratory, SIO
Acoustic monitoring for marine mammals was conducted concurrently with visual observations during daylight hours on the CC1202NH cruise. A six-element hydrophone array was towed during daylight transits between stations, and expendable Navy sonobuoys were deployed upon arrival at stations. Two marine mammal observers were present on the bridge during all daylight transits. Acoustic signals from the hydrophone array and sonobuoys were continuously recorded and monitored by the acoustician.
The six-channel hydrophone array was deployed during all daylight transits where at least 1.5 hours of data could be recorded. The array was towed 300 meters behind the ship and about 20 meters below the surface. Acoustic signals from the hydrophone array were continuously recorded and monitored by the acoustician. Channels 4 and 5 of the array were sampled at 500 kHz with a National Instruments UNB-6251 data acquisition device and recorded through ADC Pipe and Logger 2000. Channels 1, 3, and 6 of the array were sampled at 192 kHz by a MOTU 896 HD device and were recorded, monitored, and localized using Ishmael. During acoustic detections, phone-pair bearing calculations were performed by Ishmael using phones 1 and 6. The acoustician used Whaltrak to plot the animals’ bearings relative to the ship, and bearings were reported to the visual observers once the animals had passed the beam to potentially obtain species ID and group size.
Two Navy 53F sonobuoys were deployed at each daytime station to record and detect whale and dolphin vocalizations. One buoy was set to Directional Frequency Analysis and Ranging (DiFAR) and sampled at 4800 Hz, and the other to Calibrated Omni (CO) and sampled at 40 kHz. Sonobuoys were set to eight hours, either 90, 200, 400, or 1000 feet, and a selected VHF carrier frequency. The signals were received by either a preamplified omnidirectional or yagi antenna, which was connected to two ICOM R100 radios (one for each sonobuoy). Each radio was connected to its own Sound Blaster sound card, both of which were connected to the computer. Sonobuoys were recorded via Logger 2000 and monitored via Ishmael. While monitoring, the acoustician viewed two running spectrograms for each sonobuoy: one ranging 0-200 Hz for low frequency baleen whale calls (CO and DiFAR), one ranging 0-3 kHz for humpback and sperm whales (DiFAR only), and one ranging 0-17 kHz for dolphin whistles (CO only).
In total there were 22 array and 49 sonobuoy deployments (Figure 1) on this cruise. Throughout all of the hydrophone array deployments, 32 acoustic signals were detected (Figure 2) and recorded by the acoustician, 4 of which had corresponding sightings by the visual observers. During the sonobuoy deployments, 41 total detections were logged, none of which had visual confirmation. Notable recordings include Dall’s porpoise (Phocoenoides dalli) clicks (Figure 3), humpback whale (Megaptera novaeangliae) song (Figure 4), possible northern right whale dolphin (Lissodelphis borealis) burst pulses (Figure 5), Risso’s dolphin (Grampus griseus) clicks, sperm whale (Physeter macrocephalus) clicks, and fin whale (Balaenoptera physalus) calls.
Figure 1. Acoustic Effort.
Figure 2. Acoustic Detections.
Figure 3. Spectrogram of Dall’s porpoise clicks recorded on towed array on 2/4/12.
Figure 4. Spectrogram of humpback whale song recorded on a sonobuoy on 2/5/12.
Figure 5. Spectrogram of possible northern right whale dolphin burst pulses recorded on a sonobuoy on 2/12/12.