Publications (WR) Water Resources 10-1987 Thermal tolerances and preferences of fishes of the Virgin River system (Utah, Arizona, Nevada) James E. Deacon University of Nevada, Las Vegas Paul B. Schumann University of California School of Public Health, Los Angeles Edward L. Stuenkel University of California, San Francisco, School of Medicine Follow this and additional works at: https://digitalscholarship.unlv.edu/water_pubs Part of the Aquaculture and Fisheries Commons, Desert Ecology Commons, Environmental Monitoring Commons, Fresh Water Studies Commons, Natural Resources and Conservation Commons, Sustainability Commons, and the Terrestrial and Aquatic Ecology Commons Repository Citation Deacon, J. E., Schumann, P. B., Stuenkel, E. L. (1987). Thermal tolerances and preferences of fishes of the Virgin River system (Utah, Arizona, Nevada). Great Basin Naturalist, 47(4), 538-546. Available at: https://digitalscholarship.unlv.edu/water_pubs/38 This Article is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Article in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Article has been accepted for inclusion in Publications (WR) by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. THERMAL TOLERANCES AND PREFERENCES OF FISHES OF THE VIRGIN RIVER SYSTEM (UTAH, ARIZONA, NEVADA) James E. Deacon1, Paul B. Schumann2, and Edward L. Stuenkel3 ABSTRACT.—Critical thermal maxima (CTM) and thermal preferenda of the common fishes of the Virgin River were examined. Differences in final temperature preferenda and CTM for species with low thermal lability (speckled dace, spinedace, roundtail chub) correspond well with differences in their distribution and abundance in the river. These species shifted their acute thermal preferences relatively little as acclimation temperature increased. For thermally labile species (woundfin, red shiner, desert sucker, and fiannehnouth sucker), the final preferendum is a less precise indicator of probable distribution. The woundfin, an endangered fish, has a high CTM (39.5 C at 25 C acclimation) and a labile acute preferendum (slope nearest 1) compared to other species in the system. The introduced red shiner likewise has a high CTM and a labile acute preferendum. In cooler temperatures, its acute preferendum shifts more rapidly than does that of the woundfin. At higher temperatures (above 15 C), the red shiner does not shift its acute preferendum as rapidly as does the woundfin. The red shiner, however, has a higher final preferendum. For thermally labile species, influence of acclimation temperature on mean preferendum, together with CTM, provides a better insight into distributional relationships within the system. In recent years, agricultural, municipal, only six native species: speckled dace (Rhi- and industrial water uses in arid regions of the nichthys osculus); flannelmouth sucker (Cato- southwestern United States have reduced stomus latipinnis); desert sucker (Cato- both stream flows and water quality. The con- stomus [Pantosteus] clarki); Virgin spinedace sequent alterations in thermal, chemical, and (Lepidorneda mollispinis mollispinis) and Vir- flow regimes, coupled with the discharge of gin roundtail chub (Gila robusta seminuda), various effluents and the introduction of non- the latter two of which are endemic subspe- native fishes, have seriously reduced many cies; and woundfin (Plagopterus argentis- native fish stocks (Deacon and Minckley 1974, simus), which is an endemic species. The Deacon 1979, Pister 1979, 1981). woundfin is listed as endangered (U.S. Fish The Virgin River in Utah, Arizona, and Ne- and Wildlife Service 1986), the Virgin round- vada is an example of such a system. Its shift- tail has been recommended for endangered ing, sandy bottoms, steep gradients, high sed- status, and the Virgin spinedace has been rec- iment loads, variable flows, large daily and ommended for threatened status (Deacon seasonal fluctuations in temperature, and 1979, Deacon et al. 1979). The red shiner, other physical and chemical characteristics Notropis lutrensis, was introduced into the are typical of desert streams (Cook 1960, Dea- Colorado River system as a bait fish in the con and Minckley 1974, Naiman 1981). Below early 1950s (Hubbs 1954). Of the 13 intro- Zion National Park, Utah, several natural duced fish species recorded from the lower physicochemical and geographic barriers dis- Virgin River (Cross 1985), only the red shiner rupt the continuity of the biotic communities. has become well established (Williams 1977, These include Pah Tempe Springs, a series of Cross 1978a). over 100 saline hot springs emerging along the Agricultural diversion and groundwater use Hurricane Fault in Utah; and the Virgin River since 1900 have reduced flows in the main- Gorge in Arizona where, during much of the stream to the extent that long stretches may year, the entire flow seeps below ground and be dry during summer months. Following reemerges in springs above Littlefield, Ari- completion of the Quail Creek Reservoir pro- zona (Sandberg and Sultz 1982). ject early in 1985, an unanticipated, dramatic The fish fauna of the Virgin River consists of increase in discharge of Pah Tempe Springs 'Department of Biological Sciences. University of Nevada at Las Vegas, Las Vegas. Nevada 89154. Environmental Science and Engineering Program, University of California School of Public Health, Los Angeles, Los Angeles, California 90024. Present address: Office of Waste Programs Enforcement, U.S. Environmental Protection Agency, Washington, D.C. 20460. Department of Physics, University of California, San Francisco, School of Medicine, San Francisco, California 94117. 538 October 1987 DEACON ETAL.: VIRGIN RIVER FISH 539 caused increases in both temperature and observed is an unambiguous endpoint, eco- salinity throughout the downstream segment logically equivalent to death in a natural situa- of the Virgin River in Utah (Deacon, in press). tion where the animal would then be unable Summer river temperatures fluctuate by to escape lethal conditions (Fry 1971). CTMs 15-20 C daily, reaching 36 C in some areas were not measured for 15-C-acclimated suck- (Cross 1975, Deacon 1977, Schumann 1978). ers of either species (see next section). However, except for the roundtail (Schumann 1978) and Virgin spinedace (Espinosa and Thermal Preferendum Deacon 1978), the temperature responses of Acute preferred temperatures (Reynolds the native fishes have not been examined. and Casterlin 1979) were determined for six This paper reports preliminary investiga- individuals of each species (except the suckers tions of the temperature tolerances and pref- and the roundtail chub) at all acclimation tem- erences of the native fishes and the intro- peratures. Testing was done in a horizontal duced red shiner. gradient consisting of three 20-liter aquaria joined lengthwise and partitioned to give six METHODS AND MATERIALS small chambers, each 16 x 20 X 21 cm. One end was cooled by plastic-coated copper coils Collection and Maintenance of Specimens through which refrigerated water was circu- Suckers, spinedace, speckled dace, wound- lated, while the other end was heated with fin, and red shiners were collected during 100-W aquarium heaters. Aeration in each May and June using 10-m nylon seines with cell prevented gas supersaturation and tem- 6.4-mm mesh. Virgin roundtail adults were perature stratification. Fish could thus choose collected between April and October. Cap- temperatures between approximately 8 C and tured fish were acclimated in aerated and fil- 35 C. Tests were observed from behind a tered 450-liter and 1100-liter aquaria, con- blind, and temperatures were measured by taining aged tap water maintained at mercury thermometers in each chamber. temperatures of 10, 15, and 25 ± 1 C, for at Preliminary tests without a thermal gradi- least two weeks before testing (Otto 1973, ent demonstrated that selection was not spa- Feldmeth and Baskin 1976, Otto and Rice tially influenced in any of the species. This 1977). Fish were maintained on a 12-hour was further avoided during the course of the photoperiod and fed Purina Trout Chow experiments by a slight shift of temperatures daily. Food was withheld for 25 hours prior to along the gradient. experimentation. All experiments were con- Two or three individuals of a single species ducted between June and August to avoid the were introduced into the chamber closest to influences of seasonality and aging (McCauley their acclimation temperature and left undis- etal. 1977). turbed for 30 minutes. Chamber tempera- tures and the distribution of the animals in the Critical Thermal Limits gradient were then recorded at 10-minute in- Tolerance of high temperature was mea- tervals for one hour, and at 20-minute inter- sured as critical thermal maximum (CTM) vals for the next two hours. The fish were then (Lowe and Heath 1969, Fry 1971, Feldmeth removed and their length and weight and Baskin 1976). The CTM was determined recorded (Table 1). for six individuals of each species at each accli- Time and resource constraints prevented mation temperature in an aerated 13-liter our collecting