Krill Distribution and Patch Structure in the Deep Basins of the Gulf of Maine Based on Multi-Sensor Survey Data


Peter H. Wiebe, Biology
Gareth Lawson, Biology
Andone Lavery, AOPE

Grant Funded 2008

Krill are common members of marine pelagic ecosystems, and in the Gulf of Maine are a key prey item for a number of predators, including whales and commercially-important fish species. The distribution of krill is highly variable, or ‘patchy,’ in space and time, and understanding the factors causing this variability is important as the patchiness limits krill availability to higher predators. Previous studies have demonstrated that krill can be locally abundant and important in the Gulf of Maine. Overall, however, relatively little is known about the biological and physical processes leading to the formation and persistence of krill aggregations, inter-annual variations in krill abundance, and the interaction of krill with its predators in this region. The long-term goals of this work are to examine the distribution, abundance, aggregation structure, and ecological importance, including availability to higher predators, of krill in the Gulf of Maine, and to develop and apply new techniques for the quantification of krill abundance. An essential first step to achieving these longer-term goals is to capitalize on existing survey datasets to test initial hypotheses, develop new ones, and identify regions for more detailed externally-funded surveying. We therefore propose here to analyze multi-sensor datasets collected during surveys of the deep basins of the Gulf of Maine conducted during the falls of 1997-1999 under the Georges Bank GLOBEC program. These surveys, which were originally designed to investigate the distribution and abundance of copepods, combined a suite of sophisticated sampling technologies, including acoustic, net, optical, and a variety of environmental sensing systems. We will take advantage of recent advances in the analysis of multi-frequency acoustic data to identify krill and other zooplankton in the acoustic record based on net and video samples and models of how the different zooplankton groups scatter sound, and will then quantify and map their abundance over broad survey areas. The objective is to assess spatial and inter-annual variability in krill distribution, abundance, and aggregation structure in relation to hydrographic conditions and bathymetric features.

This is an inter-disciplinary project, combining our expertise in ocean acoustics, zooplankton ecology, and oceanography. Successful completion of the project will supply critical new information on the factors driving variability in krill distribution and will provide leverage in seeking external funding for future survey work.