In February 2005, Dr. Mark Patterson of the Autonomous Systems Lab at the Virginia Institute of Marine Science partnered with Dr. David Demer of the Southwest Fisheries Science Center to investigate an Antarctic coastal ecosystem using the autonomous underwater vehicle Fetch 1 and other tools.
The expedition, which took place between February 1-9, explored the waters near Cape Shirreff on Livingston Island, South Shetlands.
The goal of the project was to field test the use of a small AUV like Fetch 1 in the challenging waters of the Southern Ocean. Shallow and highly variable bathymetry makes this area unsuitable for study from large ships, and the frigid and seal-infested waters make it uncomfortable and dangerous for SCUBA divers. A specific objective was to determine if Fetch 1 and its side-scan sonar unit could be used to image and identify krill swarms.
Antarctic krill, which aggregate in large swarms and layers in the waters just offshore of the island, provide the main food source for Cape Shirreff’s seasonally resident fur seal and penguin populations.
Fetch I was deployed from a Zodiac several times as a field test for more extensive deployments in future field seasons. Collected data sets were analyzed to study the relationships between the oceanography and biology of the near-shore area.
Overall, Fetch 1 dove 55 times to depths as great as 70 m, and traveled an estimated 12.1 nautical miles. During these dives, Fetch 1 collected 260 Mb of 600 kHz side scan sonar data, 4 hours of underwater video, and simultaneously logged conductivity, temperature, depth, bathymetry, and dissolved-oxygen data at 2 Hz. AUV operations were conducted from the Zodiac under varying conditions of rain, fog, high winds, and high waves.
Lessons learned for future deployments
Fetch 1 carried tags transmitting on 38 and 50 kHz, and locating the vehicle using the pinger locator proved essential on several occasions when visibility was reduced by fog and whitecaps. It was also necessary to determine when the vehicle fins were knocked around during deployments, when the vehicle inadvertently hit the bottom in uncharted areas (the altimeter onboard cannot avoid collisions with vertical cliffs), and when marine algae had fouled the AUV's propeller. It was also necessary to stay vigilant of leopard seals becoming overly interested in AUV operations and operators.