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d. Understand natural reproduction requirements and impediments of native species survival. e. Identify limitations to recruitment of all life stages of native fish. f. Establish benchmark or reference sites to monitor population trends and assess impacts from dam operations. g. Identify and prevent pathogens, parasites, and invading organisms from negatively impacting fisheries and monitor fish health. h. Assess contaminant levels in fish and aquatic food chain organisms; identify sources and protective measures. i. Explore measures to control nonnative fish populations when they negatively influence native fish. j. Promote recreational harvest of sport fish in flowing rivers. B. INFLOWS 1. Status of Inflows: Inflows are artificially created habitats formed as a result of the dam backing up waters of Lake Powell. They are the most productive aquatic habitats within the Glen Canyon NRA and support the greatest fish biomass. The inflow estuary is a bountiful nursery area for young fish and for planktivorus adults. Inflowing rivers carry a nutrient load and naturally occurring trace elements with the sediment that are deposited at the inflow. The nutrient rich waters allow development of huge plankton blooms where silt deposition allows sufficient sunlight penetration. Trace elements are incorporated into the food chain via plankton. Food chain organisms containing selenium at levels of 3 ug/g dry weight or more should be viewed as potentially detrimental to aquatic organisms that consume them. Plankton collected by NPS in 1994 at Lake Powell inflows ranged from <0.05 to 6.0 ug/g dry weight selenium. Mater clarity is highly variable depending on precipitation, snow melt runoff, and flood events. Inflows act as mixing tones between river and reservoir where native species from river habitats commingle with nonnatives from the reservoir habitats. Larval drift of native fishes spawned upstream in flowing rivers deliver early life stages to the inflows. It is likely that conditions favoring predators occur often enough to negatively impact growing young native fish attempting to survive in the inflow. Native fish presumably need timely access to river habitat to avoid predation from fish assembled in the inflow. Critical habitat has been designated within Glen Canyon NRA for endangered fish and encompasses inflow reaches of Lake Powell, both on the Colorado and San Juan rivers, including the upper San Juan Arm of lake Powell to Neskahi Canyon, and Colorado River to North Wash (USFWS, Federal Register 4/94). The intent of designating these sometimes flat water reaches of Lake Powell as critical habitat was to insure that inflow areas would be included annually at any lake level. At the lake's lowest projected water level the San Juan 11