Studies of Smallmouth Black Bass (Micropterus Dolomieu) in the Columbia River near Richland, Washington

Abstract

Observations on smallmouth black bass, Micropterus dolomieu, of the Columbia River were possible because of a transplantation program undertaken by local sportsmen and because of studies made by the U. S. Public Health Service and the General Electric Company to evaluate effects of the radioactive effluent from the Hanford reactors. The average bass caught with sport-fishing gear was 15 1/2 inches long and weighed 40 ounces. Females were larger and made up a greater portion of the catch than males. Age was from three to eleven years but seven and eight-year-old fish made up about half of the catch. Growth was rapid in spite of a short season and water temperatures below that considered optimum. Some spawning occured in sloughs as early as April, but was unsuccessful because of a subsequent drop in temperature. Fry hatched from eggs spawned in July and August when temperatures were from 60 to 75°F. Transplanted bass move about considerably, but a definite migratory pattern was not established. Some fish moved over forty miles and many returned to the place of initial capture. Radioactive materials, which originated in the effluent from the reactors, were acquired by the bass through food chains. The principal isotope concentrated in the fish and other river animals was radiophosphorus. The level of radioactivity in the bass was greatest in September and least in April. No adverse effects on bass or food organisms, attributable to radioactive effluents, could be detected. The radioactive contamination of the bass was too low to constitute a hazard to persons who might eat them.