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001753 30 support for the stock assessment models, but did make suggestions regarding additional simulation efforts associated with the model. Associated with the 2003-2004 adaptive management experiment approved by the Secretary of Interior, a program of mechanical removal of non-native fishes near the confluence of the Little Colorado was implemented in 2003. This work continued into 2004-2005 as recommended. Results from 2003 through March 2004 suggest the efficacy of mechanical removal of non-native salmonids is quite high (>50%)" but that immigration offish back into the removal reaches is substantial. Therefore, frequent removal of non-native fishes is necessary to maintain low abundance. Experimental Flows Update In December 2002, U.S. Secretary ofInterior Norton approved an adaptive management experiment to be conducted in Grand Canyon National Park. This experiment, recommended by the GCMRC, began in January 2003 and consists of eli~ments designed to provide a better understanding of both sediment and fisheries resources. As part of the current GCMRC Adaptive Management Program, a key objective is to determine whether certain policy actions are improving humpback chub juvenile survival and recruitment. A central part of the fisheries experiment includes reducing the abundance of non-native fishes in a 16.5-mile reach of the Colorado River near the confluence of the Little Colorado River (LCR; RM 56.2-72.7). This experimental manipulation has been implemented in an attempt to better understand interactions between native and non-native fishes, particularly non-native coldwater salmonids and the federally endangered humpback chub. The Grand Canyon Monitoring and Research Center, at the Direction of the Glen Canyon Dam Adaptive Management Program, began implementation of non-native fish control in the LCR inflow area of the Colorado River in January of 2003 as part of a joint federal action entitled "Proposed Experimental Flows and Removal of Non-Native Fishes." The fisheries objective of this action was to reduce the number of potential predatory and competitor fishes in habitat occupied by the federally endangered humpback chub, Gila cypha. The fish control effort uses electrofishing and had three primary purposes: · determine the efficacy of this technique to reduce and control the number of non- native fishes in critical habitat for the humpback chub, GCMRC FY2006 Annual Work Plan (Draft February 15,2005)