In the ongoing discussions of causes for the Rayburn and Fork fish kills any one who suggests that the investigation should include analysis of fish tissue and water for the presence of toxic substance is often challenged to explain why other species were not affected. The challengers put forth the hypothesis that all fish species would be affected by the presence of toxic materials as if it were an absolute truth. The premise that all fish would be affected the same doesn’t come close to the truth.

There are many references which contradict the challengers. One such reference is; “Pesticides and Aquatic Animals: A Guide to Reducing Impacts on Aquatic Systems”, authored by representatives from Fisheries and Wildlife Sciences, Virginia Tech; Office of Science, Engineering , and Technology, Carson City Nevada; Virginia Pesticide Programs, Department of Entomology, Virginia Tech and Virginia Department of game and Inland fisheries, Blacksburg Virginia.

The pesticide levels which cause fish death are typically determined by introducing a pesticide of known quantity to clean water containing a fish population. The quantity of pesticide is increased until a pesticide concentration level is reached which produces death in 50% of the resident fish population in a fixed time period ( typically 96 hours). This concentration is usually referred to as LC50 the lethal concentration affecting 50% of the population. Each experiment begins with clean water and a fresh fish population.

The reference cited above presents the LC50 value of 9.0 milligrams per liter for Carp and 0.9 milligrams per liter for blue gill. In plain English; to kill carp it took ten times more pesticide (Oxadiazon) than it did to kill blue gill. Other examples that prove that all species are not affected the same are plentiful.

If the challengers choose to ignore science they could choose to take a country boy common sense approach and do a little survey of the fish life found in heavily polluted waters. It’s not hard to find. They may find rough fish, Carp, Buffalo and Gar but game fish will be rare.

One final point; the premise that only bass have been affected can’t be substantiated.