Twelve species of fishes native to Oklahoma were each tested four times in a series of twenty bioassays, and the guppy was included in each bioassay as a reference. The 24-hour median tolerance limits (TLm's) were determined. The relative sensitivity of each species was established. In a 50/0 multiple range test, the species were grouped into the following six statistical populations: (1); (2); (3-5); (4-10); (5-12); and (6-13). In the following ranked list, numbers in parentheses (also the rank numbers of the species) indicate the statistical populations to which the species could belong with no significant difference, while, species not included in numbers in parentheses are significantly different from the population included. Fishes rank from most resistant to least resistant as: 1. Lebistes reticulatus (1); 2. Ictalurus melas (2); 3. Notemigonus crysoleucas (3-5); 4. Notropis lutrensis (3-5), (4-10); 5. Lepomis microlophus (3-5), (4-10), (5-12); 6. Pimephales notatus (4-10), (5-12), (6-13); 7. Notropis boops (4-10), (5-12), (6-13); 8. Lepomis cyanellus (4-10), (5-12), (6-13) ; 9. Lepomis megalotis (4-10), (5-12), (6-13); 10. Ambloplites repestris (4-10), (5-12), (6-13); 11. Chrosomus erythmrogaster (5-12), (6-13);. 12. I ctalurus punctatus (512), (6-13); 13. Micropterus salmoides (6-13). The suitability of each species as a test animal is considered, based on information on the life histories and observations made during these tests.
