This patchiness of copepods affects the movements of feeding right whales. This long term sampling of the Bay environment has created some surprisingly precise results. For example, right whales may begin feeding when the density of zooplankton reaches 3,750 organisms per cubic meter of water. In other words, right whales may not bother to open their mouths to filter plankton until that threshold is reached. And density is not the only factor.
Right whales seem to show a preference for certain species of zooplankton, especially copepods.
In particular, certain species of Calanus are favored. Thick patches containing Calanus may sustain aggregations of right whales for days or weeks. When Calanus is not available, right whales may target Centropges and Pseudocalanus or even Oithona and Acartia . Any one of these species may be numerous at different times and different areas over the Bay. Only through long term research can we hope to answer such questions.