Acoustics of Copepods and Micronekton in the Great South Channel

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SCOPEX (South Channel Ocean Productivity Experiment) is a multidisciplinary program to investigate springtime aggregations of right whales off New England and the interactions between these whales and their main prey, the copepod Calanus finmarchicus. The underlying hypothesis is that whales are concentrated in this limited area each spring because of unusually dense concentrations of copepods. Possible causes of the copepod aggegations include advection, elevated production, behavior, or a combination of these factors. On cruises in spring 1988 and scheduled for spring 1989, measurements were made of whale distributions and behavior (H. Winn, R. Kenney, URI), zooplankton distributions (K. Wishner, URI), phytoplankton distributions and zooplankton feeding (E. Durbin, A. Durbin, URI), acoustic biomass (M. Macaulay, NMFS, B. Frost, UW), hydrography and currents (R. Beardsley, R. Limeburner, WHOI, P. Cornillon, URI). Preliminary results from the 1988 cruise showed that (1) whale dive times were correlated with the depth of a diel migrating acoustic layer, implying that the whales were feeding on plankton in this layer. (2) Dense copepod layers could be either strongly migrating or present continuously near the surface, with both interannual and geographic variability. Whales can feed on both types of layers. (3) No well-defined eddy (a possible concentrating mechanism) was associated with the plankton aggregations. While there was come indication of very slow flow at 50m and deeper, the near-surface drifters tended to move quickly out of the area. Further analysis of 1989 cruise samples will now be pursued to complete the investigation.