8215 - Laserfiche WebLink

Home Browse Search

Land Use. Some disruption of present land use would be occur temporarily while actions are taken employ mechanical or chemical methods to control nonnative, warmwater fishes in the floodplain ponds. In general, no more than one day (actual treatment for a 0.5-acre pond would be several hours) would be required to chemically treat a pond. However, if ponds are drained, the temporary disruption will be increased according to the volume of water in the ponds and the pump capacity. An estimate of the time to drain a pond would be 3 to 5 days. Ponds that are drained and then chemically treated would require varying lengths of time to refill. In some cases, ponds can refill quickly if recharge occurs from irrigation return flows. Ground water recharge would depend upon the substrate composition, substrate saturation with water, and gravity flow. In most ponds, recharge is expected to occur within one or two weeks. About 25 ponds would be treated during 1997 over a 13-week period between July and September (Martinez and Nesler 1996). However, the scenario for treating 25 ponds is based on an idealized schedule for optimum success in accessing and chemically treating ponds during the summer months when the water temperatures are warm and a shorter exposure time to the chemical is required to effectively kill nonnative fishes. More than likely about 10 ponds will be chemically treated in 1997. Fish and Wildlife. Nonnative fish species would be removed from some floodplain ponds along the Colorado and Gunnison rivers. This would prevent the chronic escapement of nonnative fishes into the rivers where they would prey upon endangered fishes or use the river as a conduit to repopulate other backwaters or floodplain ponds. Removal of fish from floodplain ponds may improve those waters for waterfowl, shorebirds, and passerine birds. The dietary reliance on aquatic invertebrates occurs at all seasons for waterfowl because invertebrate protein and fats are important in body maintenance, egg production, brood production, molting, migration and winter survival (Bouffard and Hanson 1997). Many researchers correlated the diet overlap between fishes and waterfowl and believe that fish may be detrimental to waterfowl, fish-eating birds, and passerine birds. Piscivorous (i.e., fish-eating) fishes may compete directly with piscivorous birds by reducing the abundance of forage fishes (Woolhead 1994) and passerine birds such as swallows that depend to a large extent on emerging aquatic invertebrates (Blancher and McNichol 1988). Bouffard and Hanson (1987) suggested that introduced (i.e., nonnative) fishes, including North American species that are in waters other than their historic habitat, should be eliminated from wetlands that are important to other vertebrates such as birds. Nonnative fishes of the Family Centrarchidae are primary targets for control. The nonnative fishes in floodplain ponds along the Colorado and Gunnison rivers that are primarily targeted for control include various centrarchid species (Martinez and Nesler 1996). Largemouth bass and green sunfish were the most frequently collected piscivores in five randomly selected backwaters of the Upper Colorado River (Valdez and Wick 1983). 17