Bowfin

The bowfin is the sole surviving species of an entire order of fishes, the Amiiformes, which was diverse and widespread during the age of the dinosaurs, with numerous species known from fossils across North America, Europe, Asia, and elsewhere over a span of more than 150 million years. Every other member of that order has gone extinct, leaving the bowfin as the last living representative of a lineage that split off from the ancestors of most modern bony fish very early in fish evolution. Because its overall body form and many internal features have changed comparatively little from those ancient relatives, it serves as a valuable reference point for scientists studying the early history of ray-finned fishes.

The bowfin has a gas bladder, the internal organ many fish use for buoyancy, that in this species is highly vascularised, meaning richly supplied with blood vessels, and connected to the throat, so it can function as a crude lung. By rising to the surface and gulping air into this bladder, the bowfin can absorb oxygen directly from the atmosphere, which allows it to remain active in warm, stagnant, weed-choked water where dissolved oxygen levels are too low for most fish, and to survive for hours if stranded out of water in damp conditions. This air-breathing ability is one reason the bowfin is common in swampy habitats that other predatory fish avoid.

In spring the male bowfin clears a shallow, saucer-shaped nest among aquatic plants or roots and attracts one or more females to lay eggs in it, which he then fertilises and guards. After the eggs hatch, the young remain attached to vegetation for a few days by an adhesive organ on the snout, then form a dense, dark, tightly packed swarm, sometimes numbering thousands of tiny fish, that the male continues to protect for several weeks. He hovers over and circles the school, herding stragglers back and aggressively attacking any fish, turtle, or other threat that comes near, only leaving the young once they have grown large enough to disperse and fend for themselves.

Attitudes toward the bowfin vary. Anglers have historically regarded it as a rough fish or a nuisance, since it readily takes bait meant for more prized species, fights hard, and has soft, somewhat gelatinous flesh that many people find unappealing when cooked conventionally, though it is eaten in parts of the southern United States and its roe is now marketed as a domestic caviar. Ecologically the bowfin is a native predator that plays a normal role in its ecosystems and helps keep populations of small fish in check, and despite its fearsome reputation among anglers it is not invasive or harmful, being simply an ancient, tough, adaptable fish doing what it has done for many millions of years.