A Moored System for Understanding the Temporal Variability of Prey Fields of Deep Diving Predators off Cape Hatteras and Response to Gulf Stream Fronts DURIP

Abstract

Abstract : Fisheries acoustics are routinely used for biomass and abundance surveys and used for behavioral and ecological studies of marine organisms. Marine mammal prey surveys are typically conducted from the ocean surface during shipboard surveys using active acoustic echo sounders mounted over the side or in the hull of a research ship. The range for acoustic echo sounders is limited by the absorption of sound through the water, and is dependent on the frequency produced by the instrument. Typical prey surveys are therefore limited to providing data from only the upper couple hundred meters of the water column, and often cannot resolve prey targets at the depths of deep-diving predators like pilot whales, especially with the higher frequency instruments, which are needed to resolve small prey targets and useful in the frequency differencing techniques. The mooring system will address the temporal variability of the prey field off Cape Hatteras throughout the entire depth range observed for foraging odontocetes, e.g., pilot whales, using split beam echo sounders. Furthermore, we hope be able to resolve deep sea squids in the lower half of the water column using frequency differencing in combination with single target detection of large prey targets.