Northern Prairie Wildlife Research Center
Federally Listed Endangered, Threatened, and Candidate Species 1995
Paddlefish (Polyodon spathula)
- Status: Former Candidate (Note: As of February 28, 1996, this species is no longer listed as a Candidate species. However, it remains a species of management concern.)
- Historical Status:
- Paddlefish were formerly
abundant in the Missouri, Mississippi and Gulf Coast drainages. They were also present in the Great Lakes. Significant declines have occurred in some rivers, while increases have been documented in others. Paddlefish were once an important commercial species and even replaced sturgeon as the major source of eggs for caviar. The largest recorded paddlefish harvest was in 1899, when a total of nearly 2.5 million pounds were taken in the United States. Over the following 23 years the reported harvest decreased by 70%.
- Present Status:
- Paddlefish numbers have been greatly
reduced in large portions of their historic range, especially in the Mississippi and its upper tributaries. Paddlefish no longer exist in the Great Lakes. Paddlefish can presently be found in 22 states, including North Dakota. In North Dakota, they are present in the Missouri and Yellowstone Rivers. Spawning most likely occurs upstream in Montana and young paddlefish are carried downstream into North Dakota. A large sport fishery (snagging) for paddlefish exists in the spring at the confluence of these two rivers. In Montana, paddlefish are collected for caviar. Commercial paddlefish harvest still occurs in the Tennessee, Mississippi and Arkansas Rivers.
- The original habitat of the paddlefish consisted of large free-flowing rivers with high concentrations of zooplankton (floating, microscopic aquatic animals). Populations of paddlefish are maintained in reservoirs where the fish have access to spawning areas. Spawning areas consist of deep, rocky rapids with swift currents.
- Life History:
- Paddlefish mature between 7 and 14
years of age. Paddlefish do not spawn each year. Spawning occurs in the spring over gravel bars in swift currents at water temperatures of approximately 60° F. Successful paddlefish spawning has been positively correlated with water temperature and the length of spring flooding. The eggs are a greenish-black color. Backwater areas and tributary streams with dense concentrations of plankton are important feeding and nursery areas. Paddlefish primarily feed on plankton and aquatic insects. They feed by swimming through the water with their mouth open and their long paddle-like snout weaving back and forth. The paddle appears to contain sensory organs that enables the paddlefish to detect concentrations of food (the paddle is not used to "dig" for food as is commonly thought). Paddlefish grow rapidly in their first year of life (over 1 inch per week). Adults and can reach nearly 7 feet in length and weigh 200 pounds. Commercial fishing with nets and traps may be a leading cause of mortality.
- Aid to identification:
- Paddlefish are perhaps the
most unique fish species in North America. They vary from gray-blue to blackish-blue above and are often white on the belly and lower sides. Their snout is elongated and flattened into a paddle. The gill covers are pointed and extend far back on the sides of the body. The mouth is extremely large and toothless except in very young fish. Paddlefish have few scales and their skin is smooth, similar to that of catfish.
- Reasons for decline:
declined due to the destruction of spawning grounds, blockage of migratory movement by dams, channelization of rivers, loss of backwater habitat, stream water depletions, pollution, and commercial overharvest.
- Paddlefish are an extremely primitive form of fish having a skeleton of cartilage rather than bones. Juvenile paddlefish were collected in North Dakota as recently as 1991 in the upper portion of Lake Sakakawea. The paddlefish is currently being reviewed by the U.S. Fish and Wildlife Service for official listing as an endangered or threatened species.
- The Fishes of Missouri, by W. L. Pflieger,
1975. Published by the Missouri Department of Conservation.
The Paddlefish: Status, Management and Propagation,by J.
Dillard, K. Graham and T. Russell, 1986. Published by the
North Central Division of the American Fisheries Society.
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