Effects of Flooding on Recruitment of Roundtail Chub, Gila robusta, in a Southwestern River
2001; Southwestern Association of Naturalists; Volume: 46; Issue: 3 Linguagem: Inglês
10.2307/3672426
ISSN1943-6262
Autores Tópico(s)Hydrology and Watershed Management Studies
Resumor-Floods are an important abiotic factor regulating stream fish assemblages. Alterations to the natural hydrograph (e.g., water storage and diversion dams) which have reduced or eliminated flooding have been blamed, in part, for the decline of many native fishes in the desert Southwest. Proposals to divert water from the upper 72 km of the Verde River of Arizona have raised concerns about the sustainability of native fish populations. I examined the relationship between late winter/early spring flooding and recruitment of roundtail chub, Gila robusta, to age 1 in an unregulated section of the upper Verde River, Arizona, and determined if significant differences in mean catch per unit effort (CPUE) of age 1 roundtail chub existed over an 11-year period. A strong positive relationship between maximum mean daily discharge in yearx and mean CPUE of age 1 roundtail chub in year x,,, was apparent. Mean CPUE of age 1 roundtail chub significantly increased or remained high in years following a flood in late winter/early spring of the previous year, and significantly decreased or remained low in years without flooding. Conversely, mean CPUE of subadult/adult roundtail chub did not significantly differ among years; thus, whether or not periodic strong year-classes are needed to maintain adult populations is uncertain. Nonetheless, recruitment of roundtail chub, and possibly other native fishes, to age 1 appears to be dependent on late winter/early spring floods, and a reduction in flood frequency likely would be detrimental to native fishes. RESUMEN-Las inundaciones son un importante factor abi6tico regulador de las comunidades de peces en los rios. Las alteraciones a la hidrografia natural (por ejemplo almacenamiento de agua y presas), las cuales han reducido o eliminado las inundaciones, son en parte la raz6n por la cual las poblaciones de peces nativos estan disminuyendo en la zona del desierto del suroeste de los Estados Unidos. Los planes para desviar agua de los primeros 72 km en la parte alta del Rio Verde en Arizona, han provocado preocupaciones sobre la sustentabilidad de las poblaciones de peces nativos. En este trabajo, examine la relaci6n entre las inundaciones que ocurren al final del invierno/principios de la primavera y el reclutamiento del charal de aleta redonda, Gila robusta, hasta la edad 1 en una secci6n del alto Rio Verde que no esti controlada y determine si existian diferencias significativas en la media de la captura por unidad de esfuerzo (CPUE) de edad 1 de este charal, a lo largo de 11 afios. Existe una fuerte relaci6n positiva entre la media maxima diaria de descarga en el afiox y la media CPUE de edad 1 del charal en el afiox+1. Tambitn, la media CPUE de edad 1 del charal se increment6 significativamente o permaneci6 alta en los afios que siguieron a una inundaci6n al final del invierno/principios de la primavera del afio anterior, y tambien disminuy6 significativamente o permaneci6 baja en afios sin inundaciones. Contrariamente, la media CPUE de charales subadultos/adultos no fue significativamente diferente entre los afios. De esta manera, es incierto si se requieren o no clases de edad peri6dicamente fuertes para mantener las poblaciones de adultos. Sin embargo, el reclutamiento de charales de aleta redonda, y posiblemente de otros peces nativos, hasta la edad 1 parece ser dependiente de las inundaciones al final del invierno/principios de la primavera y una reducci6n en la frecuencia de las inundaciones probablemente seria negativa para los peces nativos. Roundtail chub, Gila robusta, like many native fishes in the desert Southwest, has been declining since the late 1800s (Miller, 1961). Competition and predation by introduced fishes (Bestgen and Propst, 1989; Marsh and Douglas, 1997) and inadvertent introductions of parasites (Brouder and Hoffnagle, 1997) have been suspected in declines of native fishThis content downloaded from 157.55.39.117 on Fri, 15 Jul 2016 06:26:43 UTC All use subject to http://about.jstor.org/terms September 2001 Brouder-Effects of flooding on Gila robusta 303 es. In addition, alterations to the hydrograph (e.g., dams, diversions, and water pumping) have negatively affected many native fishes (Minckley and Deacon, 1968; Gido et al., 1997). Floods are one of the most important abiotic factors affecting stream fish assemblages (Resh et al., 1988; Taylor et al., 1996) and are a common source of natural variation in fish density (Seegrist and Gard, 1972). Immediate negative effects of floods on fish assemblages have been documented (Harrell, 1978; Fausch and Bramblett, 1991; Lamberti et al., 1991), but the magnitude of these effects can vary (Ross and Baker, 1983; Cambray, 1991; Lob6n-Cervifi, 1996). Rinne and Stefferud (1996a) documented a significant reduction in native and nonnative fishes immediately following two floods in the upper Verde River. In both years, densities of native fish increased three-fold by the following spring, consistent with the hypothesis that native fishes recover rapidly following significant floods (Moyle and Vondracek, 1985; Matthews, 1986). Floods can affect size distribution and taxonomic composition of fish communities (Schlosser, 1985), and channel geomorphology. Floods can have a variety of deleterious effects on fishes by removal of food resources, habitat alteration, downstream displacement, and direct mortality (Harvey, 1987; Erman et al., 1988). Conversely, floods can reduce nonnative fish densities and benefit native fish communities by reducing competition and predation (Minckley and Meffe, 1987). However, timing of floods (Strange et al., 1992) and degree of habitat complexity (Pearsons et al., 1992) may reduce negative effects floods have on fishes. In addition, floods are believed to cue spawning in some fishes (Nesler et al., 1988; Poff and Allan, 1995) and remove fine sediments from spawning substrate, which may increase egg survival and recruitment (Cambray, 1991; Osmundson and Burnham, 1999). In the Verde River in central Arizona, a selfsustaining population of roundtail chub exists primarily in the upper 72 km of unregulated river upstream from the Pecks Lake diversion dam. Recruitment of roundtail chub downstream from this diversion dam is extremely low or nonexistent (K. Young, Arizona Game and Fish Department, pers. comm.). However, increased urbanization (and subsequent water demands) in the headwater region of the Verde River drainage (Prescott and Chino Valley) and plans to divert water from the upper 72 km have raised concerns about the river's ability to sustain native fish populations (Rinne et al., 1998). Several late winter/early spring floods occurred in the upper Verde River between 1988 and 1998. I hypothesized that a late winter/ early spring flood in a given year (year,) would benefit recruitment of roundtail chub to age 1 in spring of the following year (year x+l). My objective was to examine the relationship between flooding and recruitment of roundtail chub to age 1 and to discuss findings in terms of management and conservation of this declining species. MATERIALS AND METHODS-Study Area-The Verde River is one of the largest perennial rivers in the Gila River Basin, Arizona. The Verde River originates at an elevation of 1,325 m at Sullivan Lake and flows approximately 300 km in a southeasterly direction until it joins the Salt River at an elevation of 402 m (Fig. 1). Seven water diversion dams and 2 water storage reservoirs (Horseshoe and Bartlett lakes) have altered the river. The upper 72 km of the Verde River drains ca. 8,148 km2 and has base flows ranging from 0.57 m3/sec at the United States Geological Survey (USGS) gage # 09503700 near Paulden, Arizona, to 1.70 m3/sec at the USGS gage # 09504000 near Clarkdale, Arizona. Stream habitat types consist of cobble/boulder-strewn, high-gradient riffles; lowgradient riffles with pebble/gravel substrates; and runs and glides with primarily gravel and/or sand substrates (Rinne and Stefferud, 1996b). Native species [roundtail chub, Sonora sucker, Catostomus insignis, and desert sucker, Catostomus (Pantosteus) clarki] dominate the fish community, but populations of nonnative fishes (e.g., smallmouth bass, Micropterus dolomieu, largemouth bass, M. salmoides, green sunfish, Lepomis cyanellus, and red shiner, Cyprinella lutrensis) have become established (J. Rinne, Rocky Mountain Research Station, pers. comm.). Data Collection and Analyses-Only stream flow data collected from 1 January to 31 May for a given year were used in analyses because floods affecting spawning of roundtail chub occur in this time period (Neve, 1976). Historic stream flow data from 1 January to 31 May, 1988 to 1998, were compiled from USGS gage # 09504000 near Clarkdale, Arizona, to calculate mean daily discharge (m3/sec). Fish were sampled 1 to 3 times during 1 January to 31 May, 1989 to 1999, at 5 sites within the study area. Sites were chosen on the basis of accessibility, separated by 3 to 16 km, ranged 500 to 1,000 m in This content downloaded from 157.55.39.117 on Fri, 15 Jul 2016 06:26:43 UTC All use subject to http://about.jstor.org/terms 304 The Southwestern Naturalist vol. 46, no. 3 USGS Gage . # 09503700 Sullivan USGS Gage Lake # 09504000 Pecks Lake Diversion Dar SFLAGSTAFF Area of Detail
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