Comments: Diet mainly calanoid copepods and juvenile euphausiids. Feeds by skimming--swims with mouth open usually below the surface, sometimes at the surface. Depends on concentrations of zooplankton. In Bay of Fundy, appeared to exploit patches of copepods at densities greater than about 820 per cubic m (Murison and Gaskin 1989). In Cape Cod Bay, rarely fed where total zooplankton density was less than 1000 organisms per cubic meter (Mayo and Marx 1990). In the southeastern Bering Sea, fed primarily on later copepodite stages of the calanoid copepod Calanus marshallae. Historically (1940s-1960s), this population had concentrated on the oceanic copepod Neocalanus cristatus in deeper waters (Tynan et al. 2001).