The Dynamic Role of Pollock (Pollachius virens) as a Predator in the Northeast US Continental Shelf Ecosystem: a Multi-decadal Perspective

Abstract

The Northeast US continental shelf ecosystem has been subject to heavy fishing pressure and other anthropogenic influences that have directly and, through food web interactions, indirectly affected the abundance of fish and invertebrates. The role of pollock (Pollachius virens) as one of the key groundfish predators in this ecosystem has changed accordingly over the last three decades. We utilized a thirty-three year food habits database with over 5 500 pollock stomachs to examine relative removal of commercially valuable fish and invertebrate prey by pollock. Pollock diet composition has substantially shifted through time and appears closely tied to the relative availability of prey. Pollock diet shifted from euphausiids, squid and sandlance early in the time series to decapod shrimp, herrings and hakes in recent years. Both small and large size classes of pollock have shown an increased proportion of fish in the diet through time. Pollock has, at times, exerted notable predatory removals on squid, and to a lesser extent, on herring and mackerel. The implications of pollock consumption on prey population dynamics is discussed in light of the recent trend of its increasing biomass.