Copepods and Whales: Effects of Flow, Population Dynamics, and Behavior

Wednesday, April 21, 1999 - 2:00pm - 3:00pm
Keller 3-180
Glenn Flierl (Massachusetts Institute of Technology)
Right whales in their feeding grounds in Massachusetts and Cape Cod Bays enhance their rate of food intake greatly by taking advantage of the remarkable patchiness in the distribution of the dominant zooplankton species, the copepods Calanus and Pseudocalanus. The observations suggest a number of interesting hypotheses, involving a sequence of processes: (1) the tidal flows generate strong, but transient, fronts. During the convergent phase, vertically-swimming copepods will be concentrated along the fronts. (2) The concentrations become large enough that social grouping behavior can occur, leading to very intense patches or swarms (embedded in strongly sheared along-front flows and high turbulence levels, as well). (3) This social behavior can overcome the divergences in the opposite tidal phase, so that the concentrations remain high. (4) Taxis or kinesis by the whales allows them to congregate rapidly in the areas with strong patches. (5) At the same time, the zooplankton and the whales are making significant inroads on their respective food supplies. We are exploring these processes with physical and biological models to understand the conditions under whether such a sequence could occur and to see if the resulting concentrations can resemble those observed.