Three dimensional prey aggregations and fine scale foraging patterns of Humpback whales (Megaptera novaengliae) in Stellwagen Bank Marine Sanctuary. ICES CM 2007/G:04

Prior research has quantified prey densities at depth in association with foraging whales and suggests that these predators require a minimal prey density threshold for effective foraging. Even in the few cases where individual whales have been the focus of a directed study, however, it has been difficult to observe the behavior of individual whales in a three‐dimensional environment. We addressed such information gaps directly by employing a novel research approach to study the fine‐scale behavior of Humpback whales (Megaptera novaeangliae) and simultaneously measuring the distribution and density of their prey, sand lance (Ammodytes americanus). Non‐invasive multi‐sensor acoustic data logging tags measured whale movement and behavior in three dimensions. Concurrent synoptic prey data were collected using 120 and 38 kHz EK60 echosounders with simultaneous ADCP measurements of current direction and velocity. CTDs were used to measure vertical profiles of the water column during feeding bouts. Combining these measurement techniques allows us to monitor and quantify changes in whale foraging relative to oceanographic and prey conditions. Determining threshold densities of prey required for whale foraging, the effects of predation on prey school size and behavior, and examining the effects of oceanographic conditions on predator‐prey interactions can augment knowledge regarding foraging theory of top predators in marine systems.