Fine-scale Survey of Right and Humpback Whale Prey Abundance and Distribution

Abstract

Abstract : The long-term goals of this project are to describe the distribution and abundance of zooplankton prey over small spatial and temporal scales, and to provide this information to scientists studying whale behavior. We are working closely with scientists studying the behavior and movement of both right and humpback whales. The combination of the two data sets will provide us with information into how the behavior of marine mammals is affected by their prey. This project measured the abundance and distribution of the major prey species (zooplankton and nekton) of humpback and right whales as well as the spatial and temporal scales (relevant to foraging and feeding marine mammals) that the preyfield varies over. Without this information, behavioral studies of marine mammals and their responses to various stimuli may be limited in their conclusions, as food presence and availability are extremely strong factors in determining marine mammal behavior. To collect this critical information, we identified the prey type (e.g., copepod, krill, fish) and numerical abundance of zooplankton and nekton in the vicinity of marine mammals by integrating multiple frequency acoustic survey data with net and video measurements. The distribution and numerical density of prey (in both the horizontal and vertical dimensions) relative to predator presence and behavior were measured. We measured the variability of the preyfield over length and time scales (1 m - 10s km, 10 sec - days) that are important for right and humpback whale feeding behavior and success. We also measured environmental parameters (hydrographic and meteorologic) during these surveys that may be correlated with marine mammal behavior, the presence of prey species, or subsurface acoustic scattering processes. We collected visual observations of surfacing marine mammals and their behavior during the survey that can be integrated with the preyfield data and observations from other vessels or instrumented tags.