Cape Cod Bay is the only known winter-feeding ground of the highly endangered North Atlantic right whale Eubalaena glacialis, and is thus a critical habitat for right whales. As with most coastal ecosystems, Cape Cod Bay is a dynamic system with a high degree of variability in both physical and biological parameters. However, the extent of these fluctuations and their effect on the suitability of the bay as a right-whale feeding ground are not known. This study was conducted to address

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... ty in the biological and physical environment of the bay and the possible impacts of this variability on the right whales' use of the area as a feeding ground. , the whales made very limited use of the bay compared to the other 3 yr, providing a unique opportunity for comparing conditions in the bay during this change in pattern of usage by the whales. Data on the physical and biological environment of Cape Cod Bay were collected during weekly cruises. These data indicated that there was significant interannual variation in the wind-forcing affecting Cape Cod Bay. Coincident with this variation were changes in the hydrography of the bay, suggesting that circulation patterns changed during the course of the study. Circulation changes affected the zooplankton prey of the whales either directly through changes in advection, or indirectly by affecting the production of the zooplankton.