Wildlife of the James

Ancient Air-Breathing Fish of the James

by Gabe Silver
JRA Environmental Educator

A long hot summer can be hard on fish. Fish use the oxygen that is dissolved in water just like humans need the oxygen that is mixed in with the other molecules that make up air. Oxygen gets into water when it is agitated, like in a rapid of waterfall, and when healthy underwater grasses undergo photosynthesis. Healthy rivers have enough oxygen for all their native animals.

As water is heated, it loses its oxygen. Just like a climber sucking the ‘thin’ air on a tall peak, a fish in the James River in July may be barely surviving on the oxygen-depleted water. Pollution makes it worse: when nutrients run off into the river and cause algae to grow and decay, the water loses even more oxygen.
While most fish can’t tolerate severely oxygen- depleted water, a special few have tricks up their sleeves for dealing with this situation: they can breathe air. Two examples of such fish are native to the James River: the bowfin and the longnose gar.

Both of these fish are considered ‘living fossils’- genetic relics of types of fish that existed long ago. The ability to come to surface and actually use the oxygen in the atmosphere was important in the ancient aquatic habitats these fish evolved in, and proves useful today in hot, sluggish water in the summer. The gar and bowfin come to the surface to draw air into their swim bladders which are specially designed to be surrounded by many blood vessels. Oxygen diffuses into the blood vessels, and the fish can go on surviving. 

While bowfin live in the tidal portion of the James River and are rarely seen or caught, the gar (Lepisosteus osseus) lives throughout most of the James and can be seen frequently near the surface, particularly when the water is low and clear in the summer. The gar can grow as long as 6 ft. While the looks of this predator give some folks the willies, they are harmless to humans.

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