WSP05820 - Laserfiche WebLink

Home Browse Search

Proposed Modification to Mechanical Removal of Non-native Fish Bureau of Reclamation. U.S. Geological Survev. National Park Service '. ' . ,'J -iur;:25. 2003 Page 4 reach for non-native fish in the Colorado River below the LCR. The proposed modification would extend the original area of removal downstream to RM 72,7, adding 7 miles to the area below the LCR. Monitoring and limited electrofishing in the original removal reach (RM 56.2 -65.7) would continue at a frequency sufficient to ensure that non-native fish abundance is maintained at less than 10% of the abundance observed in January 2003. Most electro fishing and removal would be focused between river mile 65.7 and 72.7 during the fifth and sixth trips in 2003 and allocated as needed during 2004 to sustain a 90% reduction in non-natives through the entire reach (RM 56.2-72.7). To assess potential responses in HBC and other native fish populations, hoopnets would also be positioned in the expanded reach. ACTIONS REQUIRED FOR THE PROPOSED MODIFICA TlON TO MECHANICAL REMOVAL L'l ~ddition to th.i~ ~'lpple!1'.(,!1t t" thl' envirollmmtal assessment. modified permits will have to be secured from the National Park Service, Fish and Wildlife Service, and the Arizona Game and Fish Department. Reconsultation with the Fish and Wildlife Service will have to occur on effects to all species listed under the Endangered Species Act. No lands belonging to Native American tribes are involved in the downstream expansion, but tribes that previously expressed concerns over the proposed action are being consulted on this modification. EFFECTS OF THE PROPOSED MODIFlCA TlON TO MECHANICAL REMOVAL The proposed modification has several additional advantages and could be conducted at no increased cost from the original proposal. Furthermore, it could potentially increase near-term recruitment ofHBC. Advantages of this modification include: (I) reducing the amount of electro fishing that adult and juvenile HBC are subjected to in the LCR inflow area, (2) increasing the amount of hoop net sampling for juvenile HBC throughout the removal reach, (3) reducing the amount of scientific activity near the mouth of the LCR, an area of the river that is subject to high recreational use and of high cultural significance to Native Americans, and concentrating that effort in fewer river miles downstream. Some increase in contact between researchers and river runners will occur in the expansion reach, but this reach contains few sites used for overnight camping. Effect~ of the propose':! IT'.od!fic~tion 011. other r".{'nltTI'S evalnat"ci in the September 2002 . . environmental assessment are expected to be not measurably different from the effects identified in that document. Young humpback chub (HBC) entering the mainstem from the LCR almost exclusively occupy habitat downstream of the LCR. The removal area upstream of the LCR is intended largely as a buffer to reduce the likelihood of immigration downstream by non- native fishes. Extending the area of removal downstream by 7 miles could more than double the potentially improved habitat for young HBC and resultin improved survivorship. No changes in environmental effects due to the proposed modification are expected when compared with those identified for the proposed action (Department of the Interior, 2002)