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128 MUELLER Minckley et al. 1991). Much effort has gone into research, habitat restoration, and legislative protec- tion. Furthermore, recovery efforts have generally focused on the upper Colorado River basin where the razorback sucker is rare; little has been done to actively manage surviving populations or repress nonnative fish communities. The continual decline of the razorback sucker prompted Lake Mohave field biologists to adopt an active management effort to maintain razorback suckers in Lake Mohave. The group adopted a quick response management approach, rather than developing a more conventional recovery program. The goal was simple: to replace Lake Mohave's old razorback sucker population before the relict pop- ulation was lost. The purpose of this paper is to describe the development, operation, and results of a cooperative program to maintain the razorback sucker in Lake Mohave. Approach Cooperative Partnership The Native Fish Work Group (NFWG) is a co- operative effort of the Arizona Game and Fish De- partment, Arizona State University, Bureau of Rec- lamation, USFWS, National Biological Service, National Park Service, and Nevada Division of Wildlife. The NFWG and the program to save the Lake Mohave razorback sucker were conceived, created, and implemented at the field level. Partic- ipants are local biologists, many directly responsible for managing the Lake Mohave resource. The NFWG has no specific budget; work is accom- plished through the collective resources of partici- pating agencies. The NFWG meets every 4 months, or as needed, to review past work and to plan and assign future activities. Decisions are made at the lowest possible management level. Tasks are as- signed according to available expertise, resources, and function. For instance, environmental compli- ance and permits are usually handled by the Na- tional Park Service, Endangered Species Act (16 U.S.C.A. §§1531 to 1544) compliance is completed by the USFWS, construction activities are managed by the Bureau of Reclamation, and Arizona State University and the National Biological Service assist with research needs. Monitoring activities, fish col- lection, and site maintenance are generally accom- plished by personnel from all the agencies. The NFWG first drafted a research and manage- ment plan in 1990 that outlined the goals and po- tential methods for sustaining the Lake Mohave razorback sucker population. The plan is a working document that identifies and prioritizes goals while allowing for implementation flexibility. The plan is periodically updated as needed. Annual and specific task reports provide information regarding activi- ties. The program has focused resources on actual implementation rather than administrative pro- cesses. Factors influencing the program are limited re- sources, the rapid decline in razorback sucker num- bers, and time. The existing population is dying of old age and could perish by the end of this decade. The program is being expedited by using the repro- ductive potential of thousands of reservoir spawners rather than the conventional culturing practice of mass-producing fish from a small captive brood- stock. Management Concept Habitat degradation in the lower Colorado River basin has been extensive, but research suggests pre- dation is the single most important factor for re- cruitment failure in Lake Mohave (Minckley 1983; Marsh and Langhorst 1988; Minckley et al. 1991). Razorback suckers do successfully spawn in reser- voirs and other lentic bodies of water. Eggs incubate and hatch, but young razorback suckers apparently survive only in environments where nonnative pred- ators are absent or rare (Minckley et al. 1991). Razorback suckers once flourished in several newly impounded reservoirs in the lower Colorado River basin (Minckley et al. 1991). Apparently, popula- tions of razorback suckers were able to expand while reservoirs filled and before nonnative preda- tors became established. The ecology of these fish is not clearly under- stood. However, razorback suckers do spawn with the rising water from spring runoff. Prior to the channelization of the Colorado River and the cre- ation of large reservoirs, larval razorback suckers were dispersed into large, newly flooded, and highly productive nursery areas (Minckley et al. 1991). Survival may have depended on a combination of high spawner fecundity, rapid larval growth, and the dispersal of a naturally small predator community contained by seasonal low river conditions. Today, conditions are much different. Reservoirs have in- undated seasonally flooded nursery areas and have modified, but also expanded and stabilized, aquatic habitats. The early colonization of many of the lower Colorado River reservoirs by razorback suck- ers suggests the fish could tolerate some physical habitat changes. However, it appears the introduc-