Bowfin (Amia calva) are prehistoric fish with a native range spanning much of eastern North America. This species is the only living representative of the family Amiidae, which dates back to the Jurassic Period (199.6 to 145.5 million years ago)! Their range includes the Great Lakes and Mississippi River Basin drainages from Quebec to northern Minnesota and south to the Gulf of Mexico as well as the Atlantic and Gulf Coast Plain from the Susquehanna River drainage from southeastern Pennsylvania to the Colorado River in Texas.
Being found in many different places leads to many common names for bowfin, including dogfish, grindle, cypress trout, mud fish, swamp muskie, black fish, shoepic, beaverfish, and cottonfish. The common name cottonfish may just be their most interesting one! When improperly cooked and eaten, the flesh of the fish is said to ball up in your mouth like cotton, but when smoked perfectly it is considered a delicacy in southern Canada. In the southern United States, “Cajun caviar” is another popular delicacy made of bowfin eggs.
Bowfin don’t have many predators besides humans and other adult bowfin, which feed on young. They are considered generalists, meaning they eat a lot of different things, but some studies suggest that fish make up approximately 65% of an adult bowfin’s diet, with crayfish making up most of the remainder. Among their favorite prey are gizzard shad, golden shiner, bullheads, and sunfish.
Bowfin mainly hunt at night. When they find something tasty, they lunge, open their mouth, suck in their prey, and slam their jaw shut… all in 0.075 seconds!
Bowfin exhibit a bullet-shaped body which helps with their quick-strike method of hunting. They are stout-bodied with their dorsal fin—the fin on their back—extending more than half the length of their back and containing more than 45 rays! Their caudal, or tail fin, is rounded, and none of their fins have spines. Bowfin also have a prominent barbel-like flap on each nostril.
Bowfin have a large mouth with many sharp teeth!
In breeding males, this terrifyingly sharp mouth turns teal-blue, along with their fins. Below their blue mouth, you’ll find their gular plate, a bony plate that lies between the two lower jaws. Bowfin are the only fish in the Mississippi and Illinois rivers that have gular plates, but this special feature can also be found in primitive marine fish in other regions.
Bowfin can tolerate high temperatures and low oxygen levels that may kill other fishes due to their unique ability to “breath air.” Like gar fish, bowfin have the ability to surface the water and fill their swim bladder—which can function like a lung—with atmospheric air to supplement the oxygen supplied by their gills. The main function of a swim bladder is to help the fish maintain its buoyancy and not sink to the bottom or float to the top.
Bowfin coloration.
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Bowfin have beautiful coloration that has withstood the test of time.
They have a beautiful olive-green mottled coloration concentrated on their back and upper side that fades to pale-green near their belly. Their dorsal and caudal fins are dark green with darker bands of color throughout and their lower fins are brighter green.
Young bowfin sometimes have a black spot, with a yellow or orange “halo” around it, near the base of the caudal fin. Adult males are more likely to keep this coloration than females. Additionally, young bowfin often have black and orange streaks on their head and fins. Of course, color vibrancy varies with individuals.
Female adult bowfin usually reach 30 inches and male adult bowfin usually reach 18–24 inches. The longest bowfin ever caught measured 34.3 inches, and the heaviest was caught in South Carolina and weighed 19 pounds! Under natural conditions, bowfin live around 10–12 years, but in captivity, they can live up to 30 years.
Since bowfin are the last living member of the Amiidae family, there aren’t many fish in our waterways they get confused with; however, they do look similar to snakeheads, an invasive species which occurs in parks of the United States.
There are three main ways to distinguish between a bowfin and a snakehead. First, bowfin have a short anal fin that is less than half the length of their back, while snakeheads have a very long anal fin that is more than half the length of their back. Second, bowfin have a large rounded head, and snakeheads have a more pointed and flattened head. Third, a bowfin’s lower jaw is shorter than their upper jaw, and a snakehead’s lower jaw is longer than their upper jaw.
Snakeheads compete with native species for food and habitat during all of their life stages. When young, they consume zooplankton, insect larvae, small crustaceans, and the young of other fish. After maturing, they consume fish, crustaceans, frogs, small reptiles, and some birds and small mammals. The U.S. Fish and Wildlife Services warns that if snakeheads become established in North American ecosystems, they could drastically disrupt food webs. Additionally, there is concern that snakehead may transfer pathogens to native fish.
Snakeheads are not found in the regions of the Illinois and Mississippi rivers that Great Rivers Field Station researchers sample. However, being aware of these invaders is crucial to stop their spread!
Bowfin are crucial parts of our ecosystems.
Mussels reproduce by allowing fertilized eggs to brood in the female’s gills until they develop into a larvae stage called glochidia. From there, the glochidia are released by the female and attach to the gills or skin of a host fish and act as a temporary parasite. Bowfin are a host to the native mussel species known as washboards (Megalonaias gigantea). Like many native mussel species, washboards are important to our waterways, as they filter bacteria, algae, and other organic matter out of the water.
In southern Illinois, bowfin usually spawn at night from early April to May or early June in spawning areas comprised of shallow, vegetated waters. Male bowfins create nests by clearing out vegetation and silt with their mouths and fins. They work to create clean beds of rootlets, sand, or gravel for the eggs to attach to within the spawning area.
Females usually lay eggs in multiple nests and some males have multiple females visit their nest. With nests being visited by multiple females, it is common to find eggs in different developmental stages within a single nest. Once fertilization is complete, the male bowfin continuously protect the nest. After 8–10 days, the eggs hatch and the newly spawned fish (fry) remain in the nest under their father’s protection. When the young fish are able to feed they leave in a swarm and school with the male, under his protection, until they reach around four inches long.
The males aggressively defend their young and have been known to deploy trickery to protect them. Males create diversions by splashing up water or mud screens to allow the young to escape danger under the cover of sediment. By the time bowfin reach two to three years of age they are able to reproduce.
You know that hard-to-work-with coworker? We’ve all got one…
Well, ours at the Great Rivers Field Station is bowfin! These powerhouse predators can be awfully slippery when it comes time to measure them, but our seasoned crew members have it down!