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Species Interaction

River herring play an extremely important role in freshwater and marine foodwebs. In estuaries and freshwater, during the river herring migration, river herring represent an easily obtainable, high caloric value prey item for many species of fish, birds and mammals. The immigration of adult river herring and emigration of juveniles within East Coast rivers represents a feast to many predatory species. In freshwater and estuary environments river herring abundance is unmatched in terms of biomass by any other prey species within the range that river herring live. During the spring spawning migration, river herring likely contribute significantly to overall breeding success of many predators whose breeding season closely overlaps their arrival.  In the marine environment, river herring play an equally important role for many marine fishes such as striped bass, spiny dogfish, Atlantic cod and pollock; as well as many marine mammals and birds, including whales, seals, ospreys, cormorants, and gulls. In fact, in a 2008 report, Adrian Jordaan and his colleagues identify many instances where declines in abundance of many species of fish in nearshore habitats that prey on river herring, such as cod and haddock, have been attributed to declines in river herring abundance. 

Prior to ecological disturbances predation likely had a negligible effect on river herring populations. But as a consequence of environmental impacts over the last 150 years (e.g. dam construction, pollution, overfishing) that have considerably reduce river herrings’ abundance, the schools of river herring are likely considerably smaller, more spatially and temporally sporadic then historically, and subsequently more vulnerable to predation pressures.    

The effects of predation on river herring are more pronounced in recent decades particularly as striped bass populations have rebounded and as new predatory species have been intentionally or accidentally introduced. Striped bass are also anadromous and can easily take advantage of schools of river herring, particularly around dams that block or slow river herrings’ ability to migrate. River herring populations most affected by increases in striped bass populations are predominately south of Maine, where the immigration of both species into estuaries and rivers is more synchronous with one another.  

Throughout the East Coast, intentional and accidental introductions of invasive species have added to the list of predators that prey on river herring. Many species introductions were done to provide more opportunities for recreational fisheries. The more desirable introductions often include larger predatory species that offer greater entertainment value to recreational anglers. Consequential to these introductions, native fish species are threatened with increases in predation, and competition for food and space. Throughout the Mid-Atlantic and Southeast, the intentional and accidental introduction of blue catfish and flathead catfish (both native to the Mississippi River basin) has significantly increased predation on many native fauna including river herring. Blue and fathead catfish pose an additional threat to river herring over many other introduced species because of their ability to effectively use riverine, tidal freshwater, and brackish habitats. Similar to the threat of striped bass predation, catfish also gain advantage at pools below dams where river herring congregate.   

The river herring Technical Expert Working Group (TEWG) Species Subgroup has considered issues related to the above specific to the interactions between river herring and other components of the ecosystems they occupy rangewide (includes trophic interactions and ecosystem services in freshwater, estuarine and marine environments). Additional information on these discussions, including other information to inform the topic and ongoing efforts can be found at: