Zooplankton were highly concentrated in the upper 5 m of the water in aggregations that often covered multiple square kilometers and lasted for several hours. Unsurprisingly, whales were found to spend the majority of their time between 0.5 and 2.5 m below the water's surface, indicating that they most likely were following their food. Unfortunately, whales are difficult to see at this depth, making them particularly vulnerable to collisions with vessels of a range of sizes.
(The zooplankton Calanus finmarchicus, the most common species of whale prey sampled during the study.)
Along the Massachusetts coastline, a network of real-time passive acoustic buoys is used to monitor whale activity. However, these only work when the whales vocalize, which the researchers did not observe them doing throughout the course of the study. This means that an alternative monitoring technique--such as using echosounders to detect zooplankton and predict where the whales will be--may be necessary to protect these magnificent marine mammals.
Parks, S.E., Warren, J.D., Stamieszkin, K., Mayo, C.A., and Wiley, D. 2011. Dangerous dining: surface foraging of North Atlantic right whales increases risk of vessel collisions. Biology Letters, online advance publication.
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