This is the last of four articles on Kentucky’s ancient fish.
The American paddlefish (Polyodon spathula) is a member of family Polyodontidae, closely related to the two species of sturgeons in Kentucky — the shovelnose sturgeon (Scaphirhynchus platorynchus), and the lake sturgeon (Acipenser fulvescens).
Fossil records of paddlefish date back over 300 million years, nearly 50 million years before dinosaurs first appeared.
Three species of paddlefish that once lived in western North America are now extinct, which makes the American paddlefish the last surviving member of this family on the continent. There is only one other extant (still in existence) species in the paddlefish family, the critically endangered Chinese paddlefish (Psephurus gladius), in the Yangtze River basin in China.
The paddlefish is a filter feeder that lives in large turbid rivers and impoundments, using sensory receptors on its head and snout (rostrum) to locate swarms of zooplankton, its primary food source.
Easily distinguished by its long, paddle-shaped snout, that is about one-third of its body length, the paddlefish has a mostly scaleless “shark-like” body, with cartilaginous skeleton, heterocercal tail fin, and large pointed flap on the gill cover.
Adults grow to about five feet in length and can weigh up to 185 pounds. The common name for this fish throughout its range is spoonbill.
Kentucky’ state record paddlefish weighed 106 pounds and was taken from the Ohio River by William Chumbler, of Calvert City, on March 23, 2004.
Range and Distribution
Prior to 1900, the geographic range of the paddlefish included all of the Mississippi River and its major tributaries, as far east as the Great Lakes region. Today, paddlefish are found in 22 U.S. states, primarily in tributaries to the Mississippi and Missouri rivers.
Distribution in Kentucky includes large rivers statewide — the Mississippi, Ohio, Tennessee, Cumberland, Green, Salt, Kentucky, and Licking. Paddlefish are also found in a handful of major reservoirs: Kentucky Lake, Lake Barkley, and Lake Cumberland.
Life History and Biology
Paddlefish are long-lived, yet mature sexually rather late in life.
Females do not begin spawning until they are seven to 10 years old, some as late as 16 to 18 years old. Females spawn every second or third year. Males spawn more frequently, usually every year or every other year, beginning around age seven, but some fish as late as nine or 10 years of age.
Paddlefish spawn on silt-free gravel bars that would otherwise be exposed to air or covered by very shallow water most of the year.
There are three precise environmental events that must occur before paddlefish will spawn. Water temperatures must be from 55 to 60 degrees Fahrenheit, increasing day length (photoperiod), and adequate water levels over preferred spawning habitat, rises in river levels due to snow melt or spring rains that cause flooding.
Fishery scientists believe paddlefish spawning is impacted because these environmental conditions may only occur once every four to five years in major rivers.
Paddlefish are broadcast spawners, females release their eggs into the water over bare rocks or gravel at the same time males release their sperm. Fertilization occurs externally.
The eggs become sticky after they are released into the water and will attach to the bottom substrate. Incubation varies depending on water temperature, but in 60 degrees Fahrenheit water the eggs will hatch into larval fish in about seven days. After hatching, the larval fish drift downstream into areas of low flow where they forage on zooplankton.
Young paddlefish are poor swimmers which makes them susceptible to predation. Therefore, rapid first-year growth is important to their survival. Fry can grow about one inch per week, and by late July the fingerlings are about five to six inches in length.
By late September fingerlings have developed into juveniles, and are around 10 to 12 12 inches long. Studies indicate that by age five their growth rate averages around 2 inches per year depending on the abundance of food and other environmental factors.
Commercial Value
The paddlefish is a commercially important species, val- ued for its roe (eggs), which are processed and sold as caviar.
Because the importation of beluga caviar from the Caspian Sea was banned in 2005, there is added fishing pressure on paddlefish. Beluga sturgeon (Huso huso), whose roe is the source of the world’s most prized caviar, is on the brink of extinction in the Caspian Sea, Adriatic Sea, and Sea of Azov, where populations are suffering from overfishing, poaching, loss of spawning habitat and pollution.
State and federal fishery biologists in the U.S. are concerned about declines in populations of American paddlefish throughout its range, but admit that it’s very difficult to assess the population in a given state.
Paddlefish are mobile and may move hundreds of river miles in one season, so the population must be assessed basin wide. Since the paddlefish is basically a commercial species and state fish and wildlife agencies receive funding based on the sale of sport fishing licenses, they don’t have the money needed to accurate monitor paddlefish populations.
In Kentucky, paddlefish are taken by both commercial and sport fishermen.
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“In general, the paddlefish harvest in Kentucky is going down,” said Ron Brooks, director of the Fisheries Division for the Kentucky Department of Fish and Wildlife Resources. “But we consider paddlefish a population of great concern.”
Commercial fishermen use gill nets to catch paddlefish during a winter/late spring season. Most of the fishing is done in the Mississippi and Ohio rivers, although Brooks said 25 permits are issued for a special paddlefish netting season in Lake Barkley and Kentucky Lake.
Commercial fishermen must buy special permits to harvest roe-bearing fish and submit daily transaction reports on the roe-bearing fish they harvest.
Buyers of roe-bearing fish must also buy special permits and submit reports monthly detailing the transactions. There are six (three non-resident) roe-bearing fish buyers licensed in Kentucky.
“Kentucky is number one in caviar production,” said Brooks. “Most of the caviar (from Kentucky paddlefish) is sold domestically.”
Paddlefish eggs mature in the late fall and must be harvested before the spring spawn.
Sport fishermen can snag paddlefish with a weighted treble hook during a statewide season, Feb. 1 through May 10 (two-fish daily creel limit), but it’s illegal to sell paddlefish flesh or their roe when taken by this method.
The paddlefish is a “living fossil,” one of Kentucky’s remarkable ancient fish.
Art Lander Jr. is outdoors editor for NKyTribune and KyForward. He is a native Kentuckian, a graduate of Western Kentucky University and a life-long hunter, angler, gardener and nature enthusiast. He has worked as a newspaper columnist, magazine journalist and author and is a former staff writer for Kentucky Afield Magazine, editor of the annual Kentucky Hunting & Trapping Guide and Kentucky Spring Hunting Guide, and co-writer of the Kentucky Afield Outdoors newspaper column.