RUI: Improving Acoustic Estimates of Antarctic Krill Populations

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Antarctic krill are a vital link in the food web of the Southern Ocean. In addition to serving as prey for the higher trophic levels (birds, pinnipeds, whales), they are also harvested commercially by several different nations. As a part of this management strategy, numerous acoustic surveys of the krill stock are conducted annually. While acoustic methods provide several advantages over other sampling techniques, the conversion of acoustic backscatter information to numerical abundance of animals is a difficult problem. This project seeks to improve the accuracy of acoustic surveys of Antarctic krill by using a small-boat survey to collect acoustic, meteorological, hydrographic, and video observation data. By utilizing the United States Antarctic Marine Living Resources (AMLR) Program's chartered research vessel, this project will sample off- and on-shelf regions around Livingston Island focusing on two submarine canyons which flank Cape Shirreff, Antarctica. An array of five spar buoys will be constructed and deployed in these waters to collect long (weeks to months) time-series of ADCP and acoustic backscatter data. These data, along with the hydrographic information from the small-boat survey, will be used to determine whether Upper Circumpolar Deep Water is traveling up the submarine canyons and increasing the productivity of this region. The spatial and temporal variability of this influx of deep water will be determined to understand the forcing functions which control the abundance of krill in these waters. The results from this work will improve the ability of scientists and fishery managers to use acoustic data to estimate krill abundance. Furthermore, the importance of near-shore krill populations, and the factors that control their distribution and abundance, will be better understood. This research will also improve the undergraduate educational experience of students at one of the PI's home institutions, which is an RUI. These students will not only participate in research projects involving data analysis, but instrumentation used in this project will be deployed off shore and will provide students with access to modern oceanographic sampling methods and allow them to experience the benefits and complications of collecting real-world data. These data will be utilized in several courses at the college, and the pedagogical materials developed in this endeavor will be placed on a web site for educators elsewhere to use. The buoy data will also be freely available on-line.