American paddlefish are known across the globe by many names, including spoonbill, spoonbill cat, shovelnose cat, and boneless cat. Their array of common names stem from their two most distinct features, their large spoon-like bill, or rostrum, and their lack of scales (except near their tail). Their snout is also where they get their scientific name, Polyodon spathula. Polyodon translates to “many tooth” in Greek, and most likely refers to the numerous long gill rakers on a paddlefish. Spathula means “spatula” or “blade” in Latin, referring to their large rostrum.
So what do these features do for the paddlefish?
Well, scientists believe that paddlefish use their paddle, or rostrum, to find food! Paddlefish’s specialized rostrums are covered in electroreceptors which help the fish detect nearby swimming plankton in the surrounding water. This special adaptation is necessary because paddlefish only have small, underdeveloped eyes and therefore do not rely on their vision to catch their prey.
Essentially, plankton send out a weak voltage by swimming. Paddlefish can detect these signals and know where to open their mouths nice and wide! The food passes through their elaborate gill rakers, which are somewhat like the prongs on a garden rake. They capture and hold food until it can be flushed down the fish’s throat and into their stomach with more water. Paddlefish are also known to consume insects and small crustaceans, but their primary food source is zooplankton.
The paddlefish’s closest relatives are sturgeon fish.
Although paddlefish are not related to catfish or sharks, the species can sometimes be confused with them. Paddlefish have smooth scale-less skin, just like catfish, except for a small patch of scales on their caudal fin. This misconception is where many of the paddlefish’s common names come from, such as spoonbill cat. Additionally, paddlefish somewhat resemble sharks with their heterocercal caudal fins. A heterocercal caudal fin is a tail fin that has two asymmetrical lobes. Another trait paddlefish share with sharks is their skeleton! Both sharks and paddlefish’s skeletons are made up of cartilage instead of bone, which makes the species lighter in weight as cartilage has about half the density of bone. However, paddlefish’s jaws are comprised of bone, unlike many shark species. Interestingly, cartilage does not preserve as well as bone in the fossil record, which may lead to a gap in knowledge of how indigenous people used these species.
Paddlefish are more than just curious-looking creatures, they play important economic, ecological, and aesthetic roles.
For instance, a single paddlefish can lay up to 600,000 eggs per season, and humans love to eat them! Roe, also known as hard roe, is the technical term for fish eggs, however, caviar is specifically the term for fish eggs from the Acipenseridae family. The Acipenseridae family, comprised of sturgeon, and the Polyodontidate family, comprised of paddlefish, are both closely related and found in the Acipenseriformes order. The paddlefish’s close relation to the sturgeon family made them a suitable substitute for the caviar industry after sturgeon stocks were beginning to deplete. This eventually led to legal and illegal overharvest and depletion of American paddlefish for their roe. In 1899 it is estimated that 2.5 million pounds of American paddlefish was harvested in the United States. Originally there were five species of paddlefish that presided in the Polyodontidae family, and the American paddlefish is the lone survivor, as the Chinese paddlefish recently was declared extinct in the early 2000s.
These highly prized eggs take a lot of energy for paddlefish to produce and fertilize! Paddlefish often spawn over gravel substrate within free-flowing large rivers, which provides oxygen to the eggs and keeps silt from building up on them. When water temperatures reach between 50–61 degrees Fahrenheit spawning begins. Male and female paddlefish are stimulated by increased water flows and they gather over the gravel beds. The males release their sperm, also known as milt, in the water column at the same time the eggs are released from the females. The fertilized eggs then fall to the gravel bed below and stick to the first thing they come in contact with. Eggs hatch after 7 days and the larvae almost immediately begin swimming so the river current can catch them and carry them to deeper pools to develop and feed. While young paddlefish aren’t born with their special rostrum, they do begin to grow rapidly starting two to three weeks after hatching.
Paddlefish also play an important ecological role. Once they reach adulthood they do not have many predators other than humans and, in some regions, American alligators. However, sauger, walleye, and channel catfish all consume larval or juvenile paddlefish as a vital source of food.
In addition to their large economic and ecological roles, paddlefish also provide another service to us—an aesthetic one! American paddlefish have a shark-like tail, elongated body, and a paddle-shaped rostrum, or bill. The bill is usually more than one-third of the total length of their body. Their underdeveloped eyes sit behind their wide mouth, and they do not exhibit teeth as adults. American paddlefish often have a black back that fades to bluish-gray on their sides and lightens to white on their belly.
Their special features and neat coloration make them an exciting species to target while fishing, but so does their size! Paddlefish are considered one of the largest North American freshwater fishes as they can weigh around 160 pounds or more and can reach lengths of around seven feet! Some individuals have even been known to grow closer to 10 feet in length! In suitable habitats, paddlefish in Illinois and Missouri often exceed 60 pounds.
Unfortunately, this unique species isn't as widespread as it once was.
The American paddlefish was petitioned to be listed as threatened under the Endangered Species Act in 1989, but was rejected due to a need for more biological information. Many sources suggest that the species had a drastic decline beginning in the early 1900s due to overharvest, habitat modification, and additional stressors. Today the species continues to decline in some regions, yet seems to be increasing in others.
It can be found in 22 different states that make up parts of the Mississippi River drainage basin. It is found from New York to central Montana and south down to Louisiana; Gulf Slope drainages from Mobile Bay, Alabama to Galveston Bay, Texas.
Previously paddlefish could be found in Lake Erie drainages in Ohio but has been extirpated from the Great Lake basin. It was also found in four other states (Maryland, New York, North Carolina, and Pennsylvania), the Great Lakes, and parts of Canada. However, reintroductions were initiated in New York and Pennsylvania in the late 1990s.
Where paddlefish are surviving really depends on habitat. Adult American paddlefish are found in quiet, slow-moving waters with access to a lot of zooplankton, which is what they eat. However, paddlefish are potamodromous, meaning they migrate within freshwater. During spawning, they need to be able to migrate to large, free-flowing rivers with gravel bars, preferably free of silt. American paddlefish can travel up to 2,000 miles in a river system, and individuals tagged in Oklahoma have been captured in areas as far away as Tennessee!
Historically the Mississippi River was free-flowing with many oxbows and backwaters, and the main channel of the river was accompanied by surrounding side channels with access to gravel bars. The Mississippi River has undergone substantial changes including channelization (a process of deepening and widening a river to increase its size, and may also include straightening the waterway), levee construction, and dam construction. Now, some large areas of artificial impoundments—areas of pent-up water—created by dams are providing suitable conditions for paddlefish feeding habits, but still reduce their connectivity.
In 1992 the United States Fish and Wildlife Service created a National Plan for the management and conservation of paddlefish and sturgeon species. Additionally, the Mississippi Interstate Cooperative Resource Association (MICRA) was formed to address the needs of paddlefish and sturgeon species and to provide guidance for future management. Since then, paddlefish numbers have been increasing in most states they are present in.
A 2006 study conducted by the United States Geological Survey stated that 18 of the 26 states where paddlefish are currently or were previously found show populations either increasing or at stable levels. These increases were attributed to the increased management of paddlefish, as 12 states exhibited closed fisheries, meaning no commercial or recreational harvest was allowed. These states included Alabama, Louisiana, Maryland, Minnesota, New York, North Carolina, Ohio, Pennsylvania, Texas, Virginia, West Virginia, and Wisconsin.
Many fishers enjoy catching paddlefish in the 13 states where recreational fishing of the species is allowed. Harvesting isn't allowed in some states because of the threats the American paddlefish is facing—overharvest, habitat destruction, pressure created from invasive species that consume the same resources, and decreased water quality due to pollution from urban waste, agricultural runoff, and industrial waste.
In Illinois specifically, sport and commercial fishing is permitted and the fish is classified as stable/increasing. During 1994 paddlefish were still declining in Illinois, but have since seen a steady increase. Beginning in 1995, Illinois fisheries biologists began participating in MICRA’s paddlefish tagging project. Paddlefish data is also collected by the Long Term Resource Monitoring (LTRM) element of the Upper Mississippi River Restoration Program mainly using gill nets here at the Great Rivers Field Station!
So what can you do to help ensure this amazing species stays with us? Support, educate yourself, and educate others!
As mentioned previously, the United States Fish and Wildlife Service currently manages our rivers with this species in mind. You can help support their mission by purchasing appropriate state fishing licenses before fishing for this species in your local area. You can also educate yourself on the status of this species, and pollution and riverine management in your community that affects paddlefish. Lastly, share what you’ve learned about this amazing creature and management activities with your friends and family so they can support the American Paddlefish, too!
Check out these great links for more paddlefish information: