9559 - Laserfiche WebLink

Home Browse Search

' use pesticides. Local authorities were notified prior to piscicide application either via a written document (Application for Fish Control and Operations Plans) or by phone. r Ponds were either allowed to detoxify naturally or were detoxified with KMn04 or sodium thiosulfate when rotenone or chlorine was applied, respectively. ' Toxicant application was always supervised by a lead aquatic biologist who was certified by the Colorado Division of Plant Industry (CDOPI) as a "Qualified Supervisor", and trained to evaluate Aquatic Pest (Commercial Category 108) problems. Other permanent and seasonal CDOW employees assisting with chemical applications were ' also trained to comply with CDOPI specifications for "Applicator Technicians". Applicators wore appropriate safety gear to minimize chemical exposure. Fish carcasses resulting from piscicide application were not removed. An attempt was made to enumerate dead fish, but due to turbidity restricting visibility in most ponds, ' erratic distribution of dead fish on the bottom of ponds, and deposition of carcasses in ' windrows, this activity was abandoned. Several cages of live fish placed at different depths and locations in treated ponds served as indicator fish to determine the presence of toxicant following reclamations. Indicator fish were replaced daily until they lived 24 hours at which point it was determined the pond was no longer toxic. ' In addition to chemical reclamations NNFC treatments included installation of screens, water management, installation of black plastic, and rerouting of irrigation water. Inlet or outlet screens of varying designs were installed on ponds to control the movement of nonnative fish from ponds into the rivers or the re-invasion of ponds by ' nonnative fish following reclamations. Though many screen designs are available and described in the literature (Bestgen et al. 2001; Miller and Who 1997; Smith 1982) it was ultimately local engineers who recommended each screen design after consideration of site specific constraints. Some ponds were dried annually in an attempt to remove nonnative fish through water management. Black plastic was spread over the surface of one small pond to remove nonnative fish as an alternative to using chemicals. Additionally, irrigation water was routed away from a reclaimed pond that also received spring water in an attempt to prevent reinvasion of nonnative fish. ' Several ponds were sampled, three to 40 months post-control (Average 19.6 months), using the same sampling technique described above to ascertain re-invasion 6