Capturing Calls: Notes from the field.
Lorenzo Scala, Lead PAM Operator, Seiche Limited.
“Having spent years working with PAM (Passive Acoustic Monitoring) systems on noisy industrial vessels around the globe, this experience with unmanned boats presents a rare opportunity for me to work from relatively quiet platforms. “C-Worker” and the smaller “C-Enduro” (affectionately referred to as ‘Junior’)-the two hard-working Automated Surface Vehicles (ASVs) towing hydrophones (underwater microphones)-are crucial to the search for cetaceans during this cruise. Their operations – indeed the entire PAM (Passive Acoustic Monitoring) system they support – require teamwork between several human players: Autonomous Surface Vehicles, Ltd., (ASV), Seiche Limited, C&C Technologies, Proteus Technologies and R2 Sonic.”
“The PAM system involves sounds being recorded and processed by equipment on the ASVs, then transmitted in real time over wi-fi to the acoustics monitoring team on the R/V Pelican. They track and monitor the sounds in real-time on computers using the software “PAMguard” that creates visual displays (spectrograms) on the computer screen; they actually watch and listen the sounds being picked up by the hydrophones being towed by Junior and C-worker.”
“Since the ASV-PAM systems are the only operations that collect and monitor acoustic data in real-time during the cruise, they give an early indication of species encounter rates in the survey area.”
“For me, combining PAM operations with ASVs was an exciting and interesting new concept in real-time monitoring. C-Worker and ‘Junior’ were expected to cruise at a speed of approximately 3 knots using a combination of solar, wind and diesel powered engines. C-Worker’s hydrophone cable was 200 m in length and towed at a depth of approximately 25-30 m. ‘Junior’ towed a shorter 50 m hydrophone cable at a depth of approximately 7 m. Both arrays contained two omni-directional broadband hydrophones and preamplifiers which enabled bearing estimates to vocalizing marine mammals to be calculated from time-of-arrival differences.”
“The teams from Autonomous Surface Vehicles, Ltd., (ASV), and Seiche Limited came together at LUMCON on the 22nd June to begin final preparations and assembly of the PAM systems. Water- tight cylindrical acoustic processing modules and towed hydrophone array cables were fitted and the final system and telemetry checks were completed on the morning of the 23rd June. That afternoon, C-Worker and ‘Junior’ were launched and set on tow behind the Pelican as she sailed out through the shallow waters from Cocodrie.”
“Upon arrival at the first EARS mooring site, the ASV’s were released from tow and the hydrophone array cables deployed
by ASV operations lead David Rutter.”
Junior takes a test spin in port and is later sent out to work in the Gulf with a hydrophone cable attached to the stern.
Aboard the Pelican, ASV operators Justin Fuselier and James Royston took control of C-Worker and Junior while Seiche operations lead Lorenzo Scala and Greggo Steward established the wi-fi connection to the vehicles and began data recording.”
“The ASV and PAM teams worked in rotating shifts to cover 24 hour monitoring and operations.”
“During the EARS mooring phase of the cruise, C-Worker and Junior sailed a holding pattern to circle within 1 km range of the Pelican. During transits between mooring sites, the ASVs cruised ahead of the Pelican where telemetry range and background levels were optimal.”
“Once deployment of all three EARS moorings were completed the Pelican and the ASVs proceeded on transects extending between each EARS site and positions to the north and east of the EARS moorings, in search of sperm whales, dolphins and beaked whales.”
“During daylight hours the ASV-PAM teams were assisted by the visual observers at ‘big-eye’ stations scanning the horizons. This assisted in the identification of mixed species groups of dolphins and confirmed distance estimates from the ASV receiver modules.”
“There was an eagerness among the scientists and ship’s crew to find some marine mammals in daylight hours. Many had not seen a whale or a dolphin in the wild and so there was excitement and anticipation particularly for the elusive deep diving species of ziphids, or beaked whales, which spend long periods foraging in the depths and only a relatively short time at the surface.”
“Throughout the time while on line transect, we searched day and night for the sounds of marine life, recording over 2 Tb of continuous raw acoustic data and logging monitoring effort and detections of marine mammal signals in a database for reference during post-processing research.”
“In real-time, we encountered sperm whales most evenings with groups of up to six individuals detected from both C-Worker and ‘Junior’s PAM systems in detection events lasting several hours. Unfortunately for the rest of the crew on board the Pelican, these encounters occurred mostly at night and only a few glimpses of animals were seen during the day. We can be sure though, that the animals were there, and they were close by at times.”
“It will be exciting to see the results from Otis glider and EARS buoys. If our real-time encounters are an indication of species occurrence rates in the area, those teams should be prepared for a lot of acoustic data from sperm whales and hopefully, even the elusive beaked whale.”