Native Fishes of Ohio

2. Paddlefish, Sturgeon, Gars, and More: Primitive and Unique Species

7 Within Ohio waters swim relict fish that were present when Tyrannosaurus rex was making life undesirable for other terrestrial forms of life. Indeed, they have changed little from their predecessors and are sometimes referred to as living fossils. Included in this group are the sturgeon, paddlefish, and gars, which represent some of North America’s largest freshwater fish. Other primitive though slightly more advanced species include the mooneyes and goldeyes in the Family Hiodontidae, the bowfin, and members of the herring family, like shad and skipjack herring. As the only extant members of Polyodontidae, paddlefish represent one of our oldest species. Fossil evidence of this unique fish predates the rise of the dinosaurs by 50 million years. Paddlefish are instantly recognized by their extremely large mouths and long paddle-shaped snouts, which can be a third of their overall length. Were it not for its head, the paddlefish would resemble a shark in form and coloration. Slate gray, it is covered by smooth skin and has a sharklike tail and a skeleton composed primarily of cartilage. These primitive fish are highly specialized filter feeders with gill rakers that can filter zooplankton and other small crustaceans from water. It was once thought that this species used its paddle-shaped snout to probe for invertebrates. Recent research has determined that a number of electrosensory receptors in the fish’s snout are used to detect weak electrical fields given off by zooplankton. Residents of the larger river systems of the Mississippi drainage, paddlefish frequent areas of slow current, especially oxbows and backwaters. Paddlefish, Sturgeon, Gars, and More Primitive and Unique Species C h a P t e r 2 8 Native Fishes of Ohio Spawning occurs in spring, during periods of high flow on gravel bars. Adhesive eggs hatch in approximately seven days, with young drifting downstream into quiet pools. Paddlefish can reach five feet in length and weigh up to eighty pounds. Females of this long-lived species do not reach sexual maturity until their ninth or tenth year, and some individuals live fifty years. Before 1900, paddlefish were common in the Ohio and Scioto Rivers; steep declines in their numbers were noted after the construction of the first dams. Today they are found in small numbers in the Ohio River downstream from Portsmouth. Nineteenth-century records show that a small population also existed in Lake Erie. Recently the species’ eggs have been targeted as a source of caviar. With the collapse of the Caspian sturgeon population, which formerly accounted for a large share of the world’s caviar, the market’s interest has focused on dwindling paddlefish populations in the upper Mississippi River. Like the paddlefish, the shovelnose sturgeon has a broad, flattened, spade-shaped snout. Its mouth is located on its ventral surface, with a row of four barbels placed between the mouth and snout. Rather than scales, this fish is covered by a series of bony plates and a long whiplike filament extending from the upper lobe of the caudal fin. The smaller of the two species, it seldom exceeds five pounds. Native to large rivers of the Mississippi and Missouri River systems this sturgeon frequents areas of moderate to swift current. A highly protrusible mouth is used to pick up a variety of macroinvertebrates and small fish. Spawning occurs in spring over gravel substrates in swift current. Females reach sexual maturity in their sixth or seventh year, with spawning occurring every few years thereafter. Recent studies indicate a maximum life span of twelve years for populations in the lower Mississippi River (Morrow et al. 1998). Shovelnose sturgeon were once abundant in the Ohio River as far upstream as Marietta in Washington County. There are no historic records or reports, however, from the lower sections of some of our larger streams. The populations began to decline following the early construction of navigation dams, and by 1950 only an occasional specimen was reported above Portsmouth. A small population of this endangered species still survives between Portsmouth and the Indiana line. In 2002, the Division of Wildlife initiated a five-year effort to reintroduce shovelnose sturgeon into the lower Scioto River. Tagged adults are occasionally reported, but to date there has been no evidence of successful reproduction. The lake sturgeon is equipped with five rows of bony plates, or scutes, and a torpedo-shaped body with a shark-like tail. It uses its spadelike snout to Paddlefish, Sturgeon...