The bigmouth buffalo ranges over most of the state where it is abundant in large rivers, some natural lakes and in the river impoundments. They rarely inhabit smaller tributary streams. Often it is found in populations with huge standing stocks, particularly in lakes and impoundments. Population densities of up to l,200 pounds per acre have been reported in Iowa.

Body color of this fish varies from bluish-green dorsally, shading to coppery-blue on the sides, then fading to a light bluish-gray belly. It has a deeply-rounded body with small eyes set close to the snout. The head is large, round, with thin lips surrounding a large, oblique mouth. The lateral line is complete with 32 to 40 large cycloid scales. The dorsal fin is sickle-shaped with 23 to 32 rays. Pharyngeal teeth are short and fragile with about l65 per arch. Adults commonly reach l5 to 27 inches in length and weigh 2 to l4 pounds. Individuals over 40 pounds are not uncommon in commercial landing. The record fish caught by hook-and-line weighed 49 pounds, l5 ounces and was caught in Cherry Lake, Tama County.

Bigmouth buffalo are well-adapted for life in shallow, standing water that is characteristic of lakes, impoundments, marshes and backwaters of large rivers. They prefer very shallow and slow-flowing water habitats over bottoms rich with detritus in mud and silt. This species tolerates very turbid waters but prefers clear, organically-enriched water with heavy algae and zooplankton blooms.

Spawning commences in April when the water temperature reaches 60 degrees F. The adult fish enter flooded marshes along river bottoms enticed by a sudden rise in water temperature or by an increasing water stage from runoff. They congregate in large schools to spawn over sedges and grasses in shallows about 2 to 3 feet deep. A single gravid female sinks to near the bottom and is surrounded by several males. Together they engage in a series of rushes that pushes the female to the surface while the adhesive eggs are broadcast and fertilized at random. The eggs are unattended until they hatch after incubating 8 to l4 days. Maturity varies, but most fish are sexually mature and spawn at age III. Fecundity of a l0-pound buffalo is around 400,000 eggs.

Growth rate of bigmouth buffalo is rapid. Specimens from the Wisconsin River had calculated body lengths of 5.2 inches at age l to 33.3 inches at age l2. Growth varies considerably with location.

The food chain of the bigmouth buffalo is quite short, utilizing mostly plankton and benthic fauna, particularly copepods and cladocerans. They compete directly with many other fish species at different stages of development. Bigmouth buffalo exhibit a definite behavior pattern to form schools. They are a hardy fish species that can endure oxygen concentrations less than l ppm and equally able to withstand warm water temperatures in excess of 90 degrees F.

*Mayhew, J. (editor). 1987. Iowa Fish and Fishing. Iowa Department of Natural Resources, Des Moines, Iowa. 323 pp.