The Life and Hard Times of the Gizzard Shad

By Dave Votaw, Photos by Joe Cornwall

 

 

Many years ago I was fishing a lake up on the Canadian Shield and observed for the first time a merciless feeding frenzy that fascinated me:  schools of ciscoes, pelagic baitfish that served as the primary forage in this lake, were being pushed to the surface by wolf packs of smallmouth bass and lake trout, not a completely unexpected strategy for feeding fish.  The surprise came from above as common mergansers, fish-eating birds with teeth, a concept only Alfred Hitchcock could love, dove into the schools of baitfish propelling themselves across the surface of the lake like harvesting machines.  I actually stopped casting to watch the carnage.

 

Years later and 800 miles south on the Ohio River I saw the same phenomenon repeated, only this time it was gizzard shad getting blasted by gulls from above and striped bass, wipers, white bass, and who knows what else from below.  But these baitfish have it worse; cat fishermen pursue shad as well with cast nets for the preferred big fish bait the oily shad are.  How do baitfish species survive such an onslaught from below and above?  Prolific reproduction.

 

Gizzard shad, Dorosoma cepedianum, colloquially known as skipjack herring or hickory shad, are members of the herring family (Clupeidae), which includes other shads such as the threadfin shad, plus the sardines and menhaden.  Gizzard shad are easily identified by the long, trailing filament at the rear of the dorsal fin; the sides are silvery blue-green with no lateral line, the tail deeply forked, and the lower jaw shorter than the upper.  Interestingly, this shad has large eyes and a dark spot near the edge of the upper gill; any crankbait fisherman will immediately recognize these triggering characteristics found on many hardbaits.

 

Gizzard shad are filter feeders straining small organisms particularly from organic deposits.  Adults have fine gill rakers to strain these minute plant plankton; the food is ground and digested in their gizzard-like stomach, hence the name.  Because of their need for bottom mud deposits, gizzard shad are found in deep, sluggish pools of rivers as well as lakes and impoundments; they prefer fertile, eutrophic waters, and avoid high gradient streams.  They are described as anadromous but only because they can be found in brackish water; gizzard shad are in fact nonmigratory.  Their native range includes the Great Lakes and the Mississippi and Ohio River drainages.

 

In late spring when water temperatures reach the 60s, the gizzard shad spawn begins at night in shallow water.  As early as age two they gather in large schools to broadcast their eggs and milt in shoreline shallows; females produce up to 400,000 eggs that adhere to plant and rock substrate, the eggs hatching in two to three days.  No nesting behavior or parental care is shown by adults.  Growth is rapid – up to seven inches in the first year – meaning that smallmouth and largemouth bass can harvest them only for a short period each spring; striped bass are the primary predators for the larger gizzard shad.  Juvenile shad, less than one inch, look and behave like a carnivore as they have teeth enabling the capture of live prey – planktonic animals (zooplankton); thus they compete with the young of other species for the same food source, and have the digestive tract to handle animal protein rather than plant.  These young shad travel in large schools for foraging and protection; prolific reproduction helps ensure continuation of the species.

 

Above one inch, a gizzard shad’s body transforms to accommodate the switch to a plant and detritus diet: longer digestive tract, loss of teeth, and gradual movement of the mouth toward the bottom side of the fish.  Adult shad pump filter water, filling the mouth and then straining the water with the gill rakers at the back of the mouth; obviously large volumes of water must be filtered to obtain adequate energy. 

 

Adults can grow to 20+ inches and four pounds, and have been reported to live 10 years; however dieoffs are common and most gizzard shad, harassed throughout their lives by aquatic, airborne, and shore-bound predators with cast nets, probably don’t survive beyond three years.

 

More information on gizzard shad can be found at these Web sites:

 

http://theriverlanding.typepad.com

http://www.fishbase.org

http://nas.er.usgs.gov

http://www.arkansasstripers.com