U.S. Fish and Wildlife Service FINAL March 2020 Species Status Assessment Report for the Colorado pikeminnow Ptychocheilus lucius U.S. Fish and Wildlife Service Department of the Interior Upper Colorado Basin Region 7 Denver, CO FINAL Species Status Assessment March 2020 PREFACE This Species Status Assessment provides an integrated, scientifically sound assessment of the biological status of the endangered Colorado pikeminnow Ptychocheilus lucius. This document was prepared by the U.S. Fish and Wildlife Service (USFWS), with assistance from state, federal, and private researchers currently working with Colorado pikeminnow. The writing team would like to acknowledge the substantial contribution of time and effort by those that participated in the Science Team. Writing Team Tildon Jones (Coordinator, Upper Colorado River Recovery Program) Eliza Gilbert (Program Biologist, San Juan River Basin Recovery Implementation Program) Tom Chart (Director, Upper Colorado River Recovery Program) U.S. Fish and Wildlife Service Species Status Assessment Advisory Group Craig Hansen (U.S. Fish and Wildlife Service, Region 6) Reviewers and Collaborators Upper Colorado River Recovery Program Directors Office: Donald Anderson, Katie Busch, Melanie Fischer, Kevin McAbee, Cheyenne Owens, Julie Stahli Science Team: Kevin Bestgen, Jim Brooks, Darek Elverud, Eliza Gilbert, Steven Platania, Dale Ryden, Tom Chart Peer Reviewers: Keith Gido, Wayne Hubert Upper Colorado River Recovery Program Biology Committee Members: Paul Badame, Pete Cavalli, Harry Crockett, Bill Davis, Derek Fryer, Tom Pitts, Dale Ryden, Dave Speas, Melissa Trammell San Juan River Basin Recovery Implementation Program Biology Committee: Ryan Besser, Harry Crockett, Stephen Davenport, Vincent Lamarra, Jacob Mazzone, Mark McKinstry, William Miller, Benjamin Schleicher, Tom Wesche, Brian Westfall, and Matthew Ziegler San Juan River Program Office Staff: Melissa Mata, Nate Franssen, Scott Durst Federal, State, and Private Collaborators and Other Interested Parties: Doug Osmundson Cover Photograph Credits a) Colorado River, Grand Canyon 1911 (National Park Service), b) upper Colorado River subbasin (U.S. Fish and Wildlife Service), and c) Green River subbasin (Utah Division of Wildlife Resources) ii FINAL Species Status Assessment March 2020 Recommended Reference U.S. Fish and Wildlife Service. 2020. Species status assessment report for the Colorado pikeminnow Ptychocheilus lucius. Department of the Interior Upper Colorado Basin Region 7, Denver, Colorado. iii Species Status Assessment Report for Colorado pikeminnow Ptychocheilus lucius Prepared by the U.S. Fish and Wildlife Service EXECUTIVE SUMMARY This species status assessment (SSA) is a comprehensive review of demographic and habitat factors for the Colorado pikeminnow Ptychocheilus lucius (Girard 1856) and provides a thorough account of the species’ overall viability. The SSA analyzes the viability of the species across three extant populations, and considers resource conditions for the lower Colorado River basin where the species is currently extirpated. The SSA provides an overview of the species’ taxonomy, life cycle, historical distribution, and listing status under the Endangered Species Act. Species needs are described at the individual, population, and species level, and needs are organized into the concepts of resiliency, redundancy, and representation. Next, the SSA provides an overview of factors that can negatively influence the species or its habitat (stressors), followed by a description of conservation measures intended to mitigate those stressors. Current condition of demographic and habitat factors for each analysis unit is summarized, providing an overall ranking of current condition for each unit. The final section summarizes projections of future conditions for each analysis unit, based on model results from a recently completed population viability analysis. Species Background The Colorado pikeminnow is the largest member of the family Cyprinidae native to North America and a species endemic to warmwater reaches of large rivers in the Colorado River basin. It was the apex predator within these reaches, and is believed to be almost entirely piscivorous as an adult. The species can grow to a large size (>1.5 m [5 ft]) and live over fifty years. Colorado pikeminnow are known to make long distance migrations for spawning and return to their home range where they inhabit deep runs, pools, and eddies. Eggs hatch within the river substrate as spring peak flows decline, with the larvae carried potentially long distances by river flows to low velocity nursery habitats downstream of the cobble spawning bars. In these reaches, larvae and juveniles seek low to zero velocity backwaters that provide warm temperatures for growth and abundant food supply in the form of macroinvertebrates and small fish prey. Individuals become sexually mature between seven and ten years of age and can spawn repeatedly as adults. Both adult and nursery habitats, as well as spawning bars, are formed and maintained by high spring peak flows that move sediment, clean cobble substrates, and maintain channel complexity to provide a diversity of habitats. Colorado pikeminnow inhabit river reaches that historically experienced extremes in both flow and temperature on an annual basis, in addition to high turbidity from sediment inputs as a result of spring snow melt or flash floods. Historically, Colorado pikeminnow occurred throughout the warmwater reaches of the Colorado River basin, including the Green, Colorado, and San Juan subbasins of Wyoming, Colorado, Utah, and New Mexico; downstream through the Colorado River mainstem in Arizona, Nevada, California, and Mexico; and the Gila River subbasin in Arizona and New Mexico. In the lower Colorado River basin (LCRB or ‘lower basin’) downstream of Glen Canyon Dam, the construction of dams and water projects diverted river flows, fragmented river reaches, reduced FINAL Species Status Assessment March 2020 peak flows, dewatered some reaches, and channelized the river starting in the early 20th century. As a result of extensive water development and modified hydrology and resultant habitats, Colorado pikeminnow were extirpated from the LCRB by the 1960s. In the upper Colorado River basin (UCRB or ‘upper basin’), including Lake Powell and its tributaries, the construction of large dams and diversions was more diffuse, leaving longer reaches of river available in downstream areas. Dams converted sections of rivers to coldwater tailraces, altered hydrology through reduced spring peaks, and presented barriers to migration. Nonnative sport fishes were also introduced into reservoirs and riverine habitats throughout the entire Colorado River basin; these species both compete with and prey upon Colorado pikeminnow. In the UCRB, Colorado pikeminnow populations exhibit contracted ranges and reduced abundances in the Green and upper Colorado river subbasins, and were functionally extirpated from the San Juan River subbasin. Population declines and extirpation from the LCRB, resulting from flow and habitat modifications and the impacts of nonnative species, led to Colorado pikeminnow being included in the 1967 List of Endangered Species and the original 1973 Endangered Species Act. Two recovery programs were established to enhance populations of the Colorado pikeminnow, one for the Green and upper Colorado subbasins, and one for the San Juan River subbasin. The Upper Colorado River Endangered Fish Recovery Program (UCREFRP) was established to maintain and recover wild, self-sustaining populations of Colorado pikeminnow in the Green and upper Colorado rivers and their major tributaries. The San Juan River Basin Recovery Implementation Program (SJRIP) has reintroduced Colorado pikeminnow through an augmentation program, with the goal of establishing a wild, self-sustaining population that is not dependent on stocking. An experimental, non-essential population of Colorado pikeminnow was also designated in the Salt and Verde rivers of the Gila River subbasin, but individuals stocked into these two tributaries since the 1980s do not appear to have established a population. The SSA examines the current and future status of Colorado pikeminnow analysis units and their habitats in the Green, upper Colorado, and San Juan river subbasins. The SSA also describes and summarizes habitat conditions in the LCRB reaches of the Grand Canyon, lower Colorado River mainstem, and the Gila River subbasin, but no demographic information is available for these extirpated populations to make an assessment of future viability in these reaches. Despite potentially suitable habitat factors, any analysis unit where the species is extirpated was considered to be in an overall extirpated condition. Species Needs The SSA considers the species’ needs during discrete life stages: spawning adults, egg and larvae within spawning substrates, age-0 and juvenile fish in nursery habitats, sub-adults, and adults. Because of Colorado pikeminnow’s complex life history, each life stage has specific and often unique resource needs. The SSA summarizes the following resources which were considered to most influence species viability: 1. Variable flow regimes, specifically peak flows to maintain channel complexity and spawning habitats 2. Base flows to provide suitable nursery habitats 3. Suitable water temperatures for spawning and growth v FINAL Species Status Assessment March 2020 4. Complex, redundant riverine habitats that provide a combination of the necessary