Laserfiche WebLink
<br />OOJ58~ <br /> <br />Chronic escapement of nonnative fish species into the rivers would continue <br />through o~tlets from the ponds or when high streamflows cause overbank <br />flooding.. The negative impacts on the endangered Colorado River fishes from <br />predation and competition by nonnative, warmwater fishes would continue. <br />This situation is not conducive to the Recovery Program goals and objectives <br />to recover the endangered fishes in the Upper Colorado and Gunnison rivers. <br /> <br />B. Alternative 2 - Mechanical or Chemical Control of Nonnative Fish Species <br />From Ponds in the Floodolain. Under this alternative, mechanical (i.e., <br />draining ponds, netting, electrofishing, etc.) or chemical (i.e., use of <br />registered piscicides) control methods would be used to remove nonnative <br />fish species from floodplain ponds along the Colorado and Gunnison rivers. <br />Mechanical or chemical control of nonnative fishes could occur in a maximum <br />of 25 ponds in 1997 and up to 150 ponds through the Year 2002 (Martinez and <br />Nesler 1996). In reality, mechanical or chemical control techniques would <br />be employed in about 10 ponds during 1997. <br /> <br />Criteria for Selectinq Ponds. Ponds will be identified as to location in <br />the floodplain (i .e., some in 10-year and 50-year floodplains). Access for <br />controll i ngnonnat i ve fi shes woul d be acqui red from 1 andowners who are <br />willing to cooperate. One objective of the proposed control measures is to <br />determine if nonnative fish control in floodplain ponds within a given river <br />reach contribute significantly to reductions in the abundance of nonnative <br />fishes in riverine nursery habitats that include backwaters, embayments, and <br />floodplain habitats that connect with the river. Therefore, the initial <br />proposed control measures are considered experimental and will be carefully <br />evaluated. <br /> <br />Oescri ot i on of Meehan i ca 1 or Chemi ca 1 Control. Ponds may be dra i ned <br />mechanically using large-volume pumps. The fish could then be seined or <br />trapped for removal if feasible. If the ponds were pumped to the point that <br />dissolved oxygen became low, the nonnative fishes would die from <br />suffocation. Water freely percolates through the gravel in some ponds where <br />complete draining would be impossible. In these ponds, the remaining water <br />treated with rotenone to kill nonnative fishes. Other ponds may be treated <br />with rotenone without draining if water recharge occurs qUickly or if it <br />would be logistically impractical to get the large pumps to the site. <br /> <br />All chemical treatments will be made using the Colorado Oivisi6n of Wildlife <br />Chemical Application Operating Procedure as standard protocol. Rotenone <br />would be applied at a concentration of 3 milligrams per liter, mg!l (parts <br />per million, ppm) following the label directions with this registered <br />piscicide. Fish absorb the chemical through the gills and are killed by the <br />interruption of respiration within the body cells (Lindahl and Oberg 1961). <br /> <br />Each crew woul d be supervi sed by a person who has been cert i fi ed by the <br />State of Colorado to apply chemicals. Rotenone has been found to be safe <br />to humans when applied by certified applicators following label instructions <br />(Sousa et ale 1987). <br /> <br />Rotenone is extremely toxic to many species of invertebrates and fish <br />(Bradbury 1986). However, the toxicity of rotenone varies among various <br /> <br />15 <br />