An occupancy‐based quantification of the highly imperiled status of desert fishes of the southwestern United States

Abstract

Desert fishes are some of the most imperiled vertebrates worldwide due to their low economic worth and because they compete with humans for water. An ecological complex of fishes, 2 suckers (Catostomus latipinnis, Catostomus discobolus) and a chub (Gila robusta) (collectively managed as the so-called three species) are endemic to the U.S. Colorado River Basin, are affected by multiple stressors, and have allegedly declined dramatically. We built a series of occupancy models to determine relationships between trends in occupancy, local extinction, and local colonization rates, identify potential limiting factors, and evaluate the suitability of managing the 3 species collectively. For a historical period (1889-2011), top performing models (AICc) included a positive time trend in local extinction probability and a negative trend in local colonization probability. As flood frequency decreased post-development local extinction probability increased. By the end of the time series, 47% (95% CI 34-61) and 15% (95% CI 6-33) of sites remained occupied by the suckers and the chub, respectively, and models with the 2 species of sucker as one group and the chub as the other performed best. For a contemporary period (2001-2011), top performing (based on AICc ) models included peak annual discharge. As peak discharge increased, local extinction probability decreased and local colonization probability increased. For the contemporary period, results of models that split all 3 species into separate groups were similar to results of models that combined the 2 suckers but not the chub. Collectively, these results confirmed that declines in these fishes were strongly associated with water development and that relative to their historic distribution all 3 species have declined dramatically. Further, the chub was distinct in that it declined the most dramatically and therefore may need to be managed separately. Our modeling approach may be useful in other situations in which targeted data are sparse and conservation status and best management approach for multiple species are uncertain.

Dynamic contributions of intermittent and perennial streams to fish beta diversity in dryland rivers

“…Rapid recolonization of formerly dry habitat is likely to occur after the cessation of drought (Lennox, Crook, Moyle, Struthers, & Cooke, ). High flow events are known to induce dispersal of native fishes elsewhere in the Colorado River Basin for increased foraging, spawning, or exploring activities (Booth, Flecker, & Hairston, ; Cathcart, Gido, & McKinstry, ; Cross et al, ), leading to decreased probability of local extinction (Budy, Conner, Salant, & Macfarlane, ). Years with the highest flow anomalies are also times when extreme spring floods or summer monsoons have occurred, and may have been detrimental to non‐native species populations (Bestgen, Wilcox, Hill, & Fausch, ; Gido, Propst, Olden, & Bestgen, ; Rogosch et al, ).…”

Matching Watershed and Otolith Chemistry to Establish Natal Origin of an Endangered Desert Lake Sucker

“…Alterations in flow regimes for agricultural and urban uses are a primary cause of habitat degradation, by reducing seasonal base flows and modifying the duration, frequency, and magnitude of high flow events . Changes in flow regimes influence the physical, biological, and abiotic conditions of the stream by altering riparian vegetation, channel morphology, habitat diversity, and temperature and dissolved oxygen patterns (Stromberg et al 2005;Budy et al 2015). Current rates of extinction for freshwater fishes are roughly 960 times greater than historic background rates from fossil record, likely due to these anthropogenic alterations (May et.…”

Evaluating the Conservation Potential of Tributaries for Native Fishes in the Upper Colorado River Basin

“…In addition, peak annual discharge was previously found to be a significant predictor of local extinction probability for three species of native fishes in the upper Colorado River basin (UCRB; Budy et al. ). Rivers that maintain other aspects of a natural flow regime, such as discharge variability and the timing, frequency, duration, and rate of change of flood and drought events are also important in native fish conservation (Poff et al.…”