Clupeids From Freshwaters of Virginia, by Don Orth

Herrings and shads have existed on the North American continent since the Paleocene (66-56 MYBP).  The state fossil of Wyoming is an extinct clupeid fish Knight eocaena.  Clupeomorph fishes arose in the early Cretaceous Period.  All members of the Clupeidae are silvery and laterally compressed and have sharp scutes on their bellies. The countershaded coloration, silvery mirror scales, and schooling behavior are effective anti predator devices.  In the freshwaters of Virginia, you may encounter six clupeid fishes. Four are anadromous species that spend most of their life cycle in salt water while the other two are freshwater. All the herrings and shads are highly prolific and their abundance may change erratically. The anadromous species are particularly important because they transfer marine-derived nutrients to freshwater in addition to serving as prey for numerous coastal birds, mammals, and fishes.   

The American Shad Alosa sapidissima is the largest of the clupeids. The flesh and roe of the American shad is highly sought as food, hence the specific epithet means "most savory."   The lower jaw shape and mouth are key characteristics to distinguish them from Hickory Shad Alosa mediocris.   American Shad spawn in rivers from Canada to Florida.  American Shad commercial fisheries were important to the history of the American colonies.  John McPhee's The Founding Fish (2002) blended descriptions of the natural history of the American Shad with American history and our obsession with this fish.  George Washington fished for American Shad in the Potomac River.  During the Revolutionary War, Washington and his troops were spending winter near the Schuylkill River at Valley Forge and replenished their food supplies with an early run of American Shad. 

Unfortunately, landings of American Shad peaked in 1897 and have declined ever since.   Major causes of declines were overfishing, construction of dams, pollution, concentrated commercial fisheries near the mouths of rivers (Mansueti and Kolb 1953).   By 1943, an estimated 77% of American Shad entering Chesapeake Bay were harvested.   In the 1950s and 1960s, the shad sport fishing increased due to popularity of spin fishing.  Recruitment overfishing was occurring for many decades before regulations were imposed (Foerster and Reagan 1977).  In the 1980s and the 1990s landings from ocean intercept fisheries doubled and mean age and incidence of repeat spawning among American Shad started to decline (Limburg et al. 2003).  Conservation efforts and dam removals were slowly implemented  and recent monitoring efforts show no signs of recovery (Lipsky et al. 2016; Hilton et al. 2017).  Stocking alone has been inadequate to increase wild populations of American Shad in the James River (Aunins et al. 2014) as concerns about inter-basin transfer of American Shad remains a serious problem.  Currently there is a harvest moratorium on American Shad in Virginia waters, although some limited bycatch is permitted.  

American Shad caught on fly rod.  Source

Head of American Shad showing shape of lower jaw.  Photo by Mitchell Blake. 

Hickory Shad is the next largest clupeid fish in Virginia. They are also known as the shad herring or the fall herring and spawn in rivers from Maryland to Florida.  Hickory Shad resemble American Shad but their distribution and feeding niche are different.  Note that in the photo below their lower jaw extends past the upper jaw when closed.  This is the easiest way to reliably distinguish Hickory Shad from the American Shad.  Hickory Shad also has fewer gill rakers than the American Shad and its diet is mainly fish and crustaceans while the American Shad is planktivorous. Sand lance, anchovies, cunners, herring, scup, silversides, and other small fish, squid, fish eggs, and even small crabs have been observed in Hickory Shad guts.   The species epithet mediocris translates to mediocre, referring to its desirability as a food fish.  

Hickory Shad. Photo by NCFishes.com

Hickory Shad (top) and American Shad (bottom).  Photo by NCFishes.com

Blueback Herring Alosa aestivalis, once known as the glut herring, historically ranged from the Gulf of St. Lawrence to the St. Johns River, Florida.   It has a blue-green colored back and silvery sides and easily confused with the Alewife.  The Alewife Alosa pseudoharengus, also known as the Gaspereau and the Branch Herring, historically ranged from Labrador to South Carolina.  Distinguishing the two species is often confusing and fisheries have lumped the two into 'river herring.'  River herring were listed as species of concern by the National Marine Fisheries Service in 2006 and a harvest moratorium was enacted in 2012.  

The two species can be distinguished.  The back of the Alewife is typically gray-green. The Alewife has a larger eye; it is broader than the distance from its forward edge to the tip of its snout.  The lining of the belly is sooty or black in the Blueback Herring and pale gray or pinkish white in the Alewife.   

The distribution and abundance of both Alewife and Blueback Herring have been highly altered by overfishing, dams, culverts, and introductions.  Both Alewife and Blueback Herring have been introduced in freshwater reservoirs to provide a land-locked populations to support many piscivorous sport fish.  However,  anadromous populations appear most at risk.  Each major Atlantic slope river supports genetically distinct populations, which show declines in abundance and mean size (Palcovacs et al. 2014).    Declines are most dramatic and widespread for the Southern New England Stock of Alewife.  Efforts are underway to reduce the incidental catch of river herrings during their coastal migrations where they overlap with Atlantic Herring Clupea harengus trawlers (Turner et al. 2017). Recently, hybridization between the Blueback Herring and Alewife raised  an additional management concern (McBride et al. 2014).  In New England,  the most heavily dammed region of the world, the freshwaters support only 6.7% of historical capacity of anadromous alewife biomass and abundance (Mattocks et al. 2017). 

Blueback Herring (top) and Alewife (bottom). Photo by Chris Bartlett.

Gizzard Shad Dorosoma cepedianum occurs in freshwater and brackish waters.  It has a deep body, with a silvery-green coloration above fading to plain silver below.  The small mouth is subterminal to inferior and it filter feeds on phytoplankton when young and switches to zooplankton as it grows larger.  A better common name might be the Bluntnose Shad, as the small blunt snout distinguishes it from other shads and herrings.   Gizzard Shad have a distinguishingly long dorsal fin ray occurs at the back of the dorsal fin.  But the 'gizzard' name refers to the muscular gizzard that aids in the breakdown of consumed foods.  Gizzard Shad may deplete zooplankton when very abundant and switch to detrital feeding.  As detrital deposit feeders they resuspend benthic nutrients into the water column where they may stimulate plankton growth.   

Gizzard Shad are readily consumed by Walleye and Black Bass, but may quickly grow beyond the size available to many predators.  Consequently, they are not the ideal forage fish for gape-limited piscivorous fish.  However, Bald Eagles, Ospreys, and Great Blue Heron can capture and eat a large Gizzard Shad. Coleman Sheehy photographed a Great Blue Heron that just captured a Gizzard Shad from James River in Richmond, Virginia.  In tidal freshwater and oligohaline sites, diet of the Osprey was 28% Gizzard Shad (Glass and Watts 2009).

Gizzard Shad. Photo by Uland Thomas. 

Gizzard Shad are widely distributed and have been introduced in many other drainages outside its native range.  They are native to all drainages in Virginia except the New River. However, they were introduced into the New River in the late 1980s.  Gizzard Shad school in large numbers and are caught with cast nets and used for cut bait by those fishing for catfish.  They rarely are hooked by anglers.  However, this rare photo proves that they can be. 

Small Gizzard Shad caught via microfishing in Lake Erie.  Photo by Sean Phillips. 

Threadfin Shad Dorosoma petenense are smaller, southern versions of the Gizzard Shad with different coloration and mouth shape. The principal distinctions are the mouth, which has a terminal position,  and the bluish-gray dorsum and yellowish coloration in caudal fin.  The upper jaw does not project beyond the lower jaw. Threadfin shad have a prominent purple to black spot on the upper side of the body just beyond the operculum and a distinguishingly long dorsal fin ray occurs at the back of the dorsal fin.   The Threadfin Shad are distributed in the lower Mississippi and other Gulf drainages, south to Guatemala.  Because of their small size, they have been introduced widely as a forage fish.  In Virginia, there are populations in Lake Anna, Back Bay, and the James drainage. Threadfin Shad are sensitive to cold temperature and often die in mass during cold winters in the northern part of the range (McLean et al. 1985). 

Threadfin Shad. Photo by Uland Thomas. 

Clupeid fishes are adapted for life in well-lit pelagic zones of lakes, rivers, and the ocean. Throughout life these fishes are eaten by numerous piscivores, including our national bird, the Bald Eagle (Markham and Watts 2008).  Anadromy, coupled with high fecundity, permits development of large populations.  Although these fishes are adapted for heavy predation mortality, the major long-term threats to population viability appear to be connectivity with spawning and rearing habitats and by catch from ocean fisheries.  

If you have been reading carefully, you should be able pass these two quizzes. 

Quiz One

Six clupeid fishes found in freshwaters of Virginia.  Name each one.

Quiz Two

One of these is an Alewife, the other is a Blueback Herring.  Which is which?

References

Glass, K.A., and B.D. Watts. 2009.  Osprey diet composition and quality in high- and low-salinity areas of lower Chesapeake Bay. Journal of Raptor Research 43:27-36.

Hilton, E. J., R. Latour, P. McGrath, B. Watkins, and A. Magee. 2017. Monitoring the abundance of American shad and river herring in Virginia's rivers 2016 Annual Report. Virginia Institute of Marine Science, College of William and Mary. https://doi.org/10.21220/V5788B

Limburg, K.E., K. A. Hattalaand, and A. Kahnle. 2003. American shad in its native range.  Pages 125–140 in K. E. Limburg and J. R. Waldman, editors. Biodiversity, status, and conservation of the world's shads, American Fisheries Society, Bethesda, Maryland, Symposium 35.

Markham, A.C., and B.D. Watts. 2008.  The influence of salinity on the diet of nesting Bald Eagles. Journal of Raptor Research 42:99-109.

Mattocks, S., C.J. Hall, and A. Jordan. 2017.  Damming, lost connectivity, and the historical role of anadromous fish in freshwater ecosystem dynamics.  BioScience 67(8):713-728. https://doi.org/10.1093/biosci/bix069

McLean, R.B., J.S. Griffith, and M.V. McGee. 1985. Threadfin shad, Dorosoma petenense Günther, mortality: causes and ecological implications in a South-eastern United States reservoir.  Journal of Fish Biology 27:1-12.

McBride, M. C., T.V.Willis, R.G. Bradford, and P. Bentzen. 2014. Genetic diversity and structure of two hybridizing anadromous fishes (Alosa pseudoharengus, Alosa aestivalis) across the northern portion of their ranges. Conservation Genetics DOI 10.1007/s10592-014-0617-9.

Palcovacs, E.P., D.J. Hasselman, E.E. Argo, SR. Gephard, K.E. Limburg, D.M. Post, T.F. Schultz, and T.V. Willis.  2014. Combining genetic and demographic information to prioritize conservation efforts for anadromous alewife and blueback herring.  Evolutionary Applications 7:212-226.

Turner, S.M., J.A. Hare, J.P. Manderson, J.J. Hoey, D.E. Richardson, C.L. Sarro, and R. Silva. 2017. Cooperative research to evaluate an incidental catch distribution forecast.  Frontiers in Marine Science  http://dx.doi.org/10.3389/fmars.2017.00116