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sunfish (0.4). For Hotspot Pond, largemouth bass (2.0), western mosquitofish (2.1), black crappie (1.2), green sunfish (0.4), and black bullhead (0.1). The following conclusions from this research were: 1) the species composition of both ponds was predominantly nonnative during all three sampling periods, 2) native fishes used the two connected ponds mostly during runoff, 3) five species of sub-adult and adult nonnative fishes moved between the two ponds that were connected to the river; white sucker and largemouth bass migrated the most between the two ponds. Roundtail chub was the only native fish to move between the two ponds, 4) within four months following draining of Gardner Pond, removal of nonnative fishes, and construction of a connection channel, nonnative fishes invaded and recolonized the pond, and within eight months, five species of nonnative fishes had successfully reproduced in Gardner Pond. Ponds in the 10-, 50-, and 100-year floodplain that have bottoms shaped and contoured as depressions are havens that provide perennial, off-channel habitats for nonnative fishes to grow and reproduce. Ponds that are depressions and that are connected to the river allow sub-adult and adult fish uninhibited access to the river and to other off-channel habitats connected to the river. Ponds with depressions provide a constant supply source of nonnative fish that can potentially escape to the mainstem river. While depressions benefit native fishes for a period only during runoff, nonnative fishes appear to benefit more from such perennial, lentic habitats, and 5) Hotspot Pond did not drain following runoff in 1996. If ponds are reclaimed, steeper bottom slopes than that found in Hotspot Pond will be required for ponds to drain during high-flow years to reduce or eliminate perennial habitat for nonnative fishes. Recommendations were to: 1) avoid connecting isolated ponds to the river that are irregular- shaped, deep depressions because such habitats provide perennial havens for nonnative fishes. If deep-depression habitats cannot be rehabilitated by recontouring and reshaping to provide seasonal, ephemeral habitat, or sloped to concentrate and harvest captive-reared fish, they should be sufficiently diked to prevent escapement of nonnative fishes such as centrarchids and ictalurids, and 2) back-fill gravel-pit ponds so that they are sloped to flood and drain seasonally and reconnect them to the mainstem river to benefit native fishes and to reduce proliferation of nonnative fishes. Such modifications would allow the floodplain to function as an ephemeral wetland and may be more cost-effective and practical for managing and controlling nonnative fishes than long-term control measures such as screening, chemical treatment, or mechanical pumping and removal of nonnative fish species. Whenever floodplain habitats are connected to the river, hydrological access for fish should be by surface connection. Underground culverts and pipes should be avoided because some native fish might be shy and will not use such structures. Alternative management options that should be considered by the Recovery Program as habitat improvements to assist recovery of Colorado River endangered fishes included: 1) coordinating Recovery Program efforts with the U. S. Army Corps of Engineers, Colorado Mined Land Reclamation, and gravel-pit companies to restore gravel-mining areas to function as historical terraces to benefit native fishes, 2) notching dikes and levees protecting gravel pits by reconnecting former floodplain habitats without deep depression ponds with the river to enhance or restore the natural function of the river ecosystem. Dikes and levees constructed to protect gravel-mining operations could be removed following gravel x