James E. Deacon

A Conservation Plan for Native Fishes of the Lower Colorado River

Abstract The native fish fauna of the lower Colorado River, in the western United States, includes four “big-river” fishes that are federally listed as endangered. Existing recovery implementation plans are inadequate for these critically imperiled species. We describe a realistic, proactive management program founded on demographic and genetic principles and crafted to avoid potential conflicts with nonnative sport fisheries. In this program, native species would breed and their progeny grow in isolated, protected, off-channel habitats in the absence of nonnative fishes. Panmictic adult populations would reside in the main channel and connected waters, exchanging reproductive adults and repatriated subadults with populations occupying isolated habitats. Implementation of the plan would greatly enhance recovery potential of the four listed fishes.

Food Partitioning among Fishes of the Virgin River

Food partitioning of one introduced and six native fishes was investigated from two different sites in the Virgin River. Replicate benthic samples from riffle areas indicated that chironomid and simuliid larvae composed the major food base available to fishes. Relativized electivity values suggest that chironomid larvae were nearly always selected over simuliid larvae by all species. Stomach analysis revealed seasonal interand intra-specific differences in diets. Desert and flannelmouth suckers fed on a mixture of sediment, detritus, filamentous algae and invertebrates. Roundtail chubs consumed largely Spirogyra, Cladophora and diatoms. Woundfin and spinedace were omnivorous, consuming an array of benthic and drift animals and plant matter. Speckled dace and red shiners were insectivorous, consuming large numbers of small dipterans. Food overlap among native fishes was uncommon, occurring in a biologically meaningful way on only four (7%) of the 55 possible occasions. Biologically meaningful food overlap (>0.60) between the exotic red shiner and native fishes occurred on four (25%) of the 16 possible occasions.

Population Size of Devils Hole Pupfish (Cyprinodon diabolis) Correlates with Water Level

Abstract Population estimates of the Devils Hole pupfish (Cyprinodon diabolis) extending over a 25-year period reveal an annual population cycle that reaches a low during spring and a high during fall. The four earliest years (1972–1976) preceded a U.S. Supreme Court water rights decision intended to protect pupfish habitat. Mean and maximum population sizes during those four years were significantly lower than during subsequent periods examined through 1997, and annual minimum population size was significantly lower during 1972–1976 than during 1991–1997. Annual maximum population size is positively correlated with water level for the month in which it occurred as well as for the month one year prior to the time of the estimate. The lowest historic water levels occurred during the period 1972–1976, and over the past 60,000 years comparable or lower water levels may have occurred only during the altithermal, about 6000 years before the present. During these two periods the Devils Hole pupfish population has probably experienced its most severe bottlenecks.

New host records for the Asian fish tapeworm, Bothriocephalus acheilognathi, in endangered fish species from the Virgin River, Utah, Nevada, and Arizona.

Bothriocephalus acheilognathi has been considered one of the most dangerous pseudophyllidean cestodes for cultured carp in Europe. This species, first described from fish in Japan, is common in the intestine of young grass carp cultured in South China. From China, cestode infections have followed grass carp imports into Europe, Russia, and the United States (Hoffman and Schubert, 1984, In Distribution, biology, and management of exotic fishes, Courtnay and Stauffer (eds.), Johns Hopkins University Press, Baltimore, pp. 233-261). To date there have been no published records of B. acheilognathi in the fishes found in the Virgin River of Utah, Nevada, and Arizona. During a preliminary survey of parasites of Plagopterus argentissimus and other endangered fish species from the Virgin River near St. George, Utah, 18% of 17 Gila robusta seminuda examined were found to be infected with the B. acheilognathi. From the same site no P. argentissimus (192) (number checked for parasites in paren-

Ecological Distribution of Fishes of Moapa (Muddy) River in Clark County, Nevada

Abstract Fish collections were made at nine stations along the Moapa River of southern Nevada. Four native species are ecologically separated into headwater and middle-stream types. The headwater fishes are ecologically segregated into one pond species (Crenichthys baileyi) and one stream species (Moapa coriacea). The apparent temperature preference for both species is near 29.5 C. Temperature range for Crenichthys is 27–32 C and for Moapa 19.5–32 C. Both Gila robusta and Rhinichthys osculus are most abundant in the turbid middle portion of the stream in undisturbed, deep riffle habitats. A fifth native species, Plagopterus argentissimus, is extremely rare or of accidental occurrence. The unsaturated Moapa River environment has been easily colonized by exotic or non-native species, most recently and most successfully by Poecilia mexicana. An additional species, Gambusia affinis, is widespread and abundant throughout much of the stream. Cyprinus carpio, Notropis lutrensis, Pimephales promelas, Ictalurus me...

Cyprinodon milleri, a New Species of Pupfish (Family Cyprinodontidae) from Death Valley, California

Cyprinodon milleri is the fifth known species of its genus found in the Death Valley system, Nevada-California. Its entire population lives below mean sea level, in what may be one of the more extreme fish habitats yet discovered. Water temperatures range from near freezing in winter to more than 40 C in summer, and the fish is capable of survival in a salinity range from 0.0 to 78.5 g/l. The new species differs from its nearest apparent relatives by having a shorter and narrower caudal peduncle, a shorter predorsal length, fewer lachrymal pores, more scales, far larger jaw teeth that lack any prominent, central ridge, and pelvic fins reduced or absent. C. milleri appears to have undergone exceedingly rapid speciation because of its extreme habitat and isolation.

The Preference of Largemouth Bass (Micropterus salmoides Lacépède) for Selected Bait Species under Experimental Conditions

Abstract The preference of largemouth bass for selected bait species was tested under experimental conditions. Three fish species and one species of larval salamander were utilized in preference experimentation: Notemigonus crysoleucas, Carassius auratus, Lepidomeda mollispinis, and Ambystoma tigrinum. Preference experiments were conducted in 2.4 and 3.0 m plastic wading pools. A total of 23 bass, varying in weight from 84–499 g, was utilized in determining single, group and replicate profiles. Replicate experimentation was conducted with previously tested bass and/or bait combinations. Twenty-five experiments were completed which included 28 trial periods (14 single and 14 group) with a total trial time of 190 days. Largemouth bass showed a significant preference for spinedace and waterdogs over golden shiners and goldfish. However, bass did not show a significant preference for either species when spinedace and waterdogs were tested against each other. Goldfish were the least preferred bait item. The or...

Fluorescent Pigment and Immersion Stain Marking Techniques for Lepidomeda mollispinis and Cyprinodon nevadensis

Abstract Two methods of marking, immersion dyeing and spraying with fluorescent pigments, were tested for use on Lepidomeda mollispinis and Cyprinodon nevadensis. Three dyes were used: Bismarck Brown Y, Rhodamine B and Trypan Blue. All three were rejected for use on L. mollispinis because of poor marking consistency and severe stress. Bismarck Brown Y was found suitable for C. nevadensis for short-term mark and recapture experiments. Fluorescent pigment marking with compressed air produced permanent marks in both species but resulted in high mortality to C. nevadensis in the laboratory.

Comparative status of fishes along the course of the pluvial White River, Nevada

-Fish populations were sampled at 11 locations along the course of the pluvial White River, southeastern Nevada, in the 1960s and in 1983, and 3 sites in early 1984. The locations included Preston Big, Preston Town, and Lund Town springs, White River Valley, White Pine County; Moorman, Hot Creek, and Flag springs, White River Valley, Nye County; and Hiko, Crystal, and Ash springs, Pahranagat Valley, Lincoln County; and Moapa Valley Water District Spring and the Moapa River at Home Ranch, Moapa Valley, Clark County. Comparisons of species composition and abundance were made and, where possible, were related to historical data on settlement and habitat modifications. Negative impacts have accelerated during the past 20 years and the fishes in most of these sites have declined dramatically because of habitat alteration and reduction, and introductions of nonnative species. One species became extinct before 1955, and our investigations show recent extirpations of taxa at two localities. Two taxa currently are listed as endangered. We submit rationale for endangered status for an additional seven taxa, threatened status for one, and special concern status for another. Only two fishes in this system presently remain comparatively safe. During late Pleistocene-early Holocene pluvial stages, the White River of southeastern Nevada flowed southward from its headwater tributaries in northern White River Valley, through Pahranagat Valley into Kane Springs Wash, cut southeastward through Arrow Canyon into Moapa Valley, joined the pluvial Carpenter River (Meadow Valley Wash) and emptied into the Virgin River above its confluence with the Colorado River (Hubbs and Miller, 1948; Miller and Hubbs, 1960; Fowler et al., 1973; Smith, 1978; Williams and Wilde, 1981). Surface flows in this system are now confined to the White River (northern White River Valley), outflows of thermal springs in White River, Pahranagat, and upper Moapa valleys, and the Moapa River which drains into the northwestern end of the Overton Arm of Lake Mead (Blackwelder, 1943; Miller and Hubbs, 1960; Fig. 1). Native fishes of this system probably were more widely distributed in prePleistocene times, but their isolation in these mostly disjunct waters for perhaps the last 10,000 years ( R. R. Miller in Williams and Wilde, 1981) has resulted in differentiation. Historical data typically are lacking in reports concerning mans impact on southwestern aquatic systems. Miller (1961), Minckley and Deacon (1968), Deacon (1979) and others summarized these impacts, and generally categorized them as activities that physically or biologically degrade habitats (e.g., habitat disturbance or introductions of exotic and other nonnative flora and fauna). Habitat alterations are known to have begun before the first settlers arrived. Selected fish populations along the course of the pluvial White River were sampled extensively during the mid 1960s by J. E. Deacon, F A. THE SOUTHWESTERN NATURALIST 30(4):503-524 NOVEMBER 27, 1985 This content downloaded from 207.46.13.169 on Sat, 01 Oct 2016 06:03:55 UTC All use subject to http://about.jstor.org/terms The Southwestern Naturalist FIG. 1.-Map of the pluvial White River drainage, southeastern Nevada. Espinosa, Jr., and B. L. Wilson using screened 44 x 23 cm baited minnow traps. In this study, data were collected during July and November 1983 and at three sites in March 1984 to compare present-day species composition and relative abundance to those found in the 1960s. Preston Big, Preston Town, and Lund Town springs, White River Valley, White Pine County; Moorman, Hot Creek, and Flag springs (and an examination of Moon River Spring), White River Valley, Nye County; Hiko, Crystal, and Ash springs, Pahranagat Valley, Lincoln County; Moapa Valley Water District (MVWD) Spring and the Moapa River at Home Ranch, Moapa Valley, 504 vol.30, no. 4 This content downloaded from 207.46.13.169 on Sat, 01 Oct 2016 06:03:55 UTC All use subject to http://about.jstor.org/terms Courtenay et al.-Status of Fishes Along White River Clark County, were the waters sampled (Fig. 1). Historical information for these sites was reviewed to determine dates of settlement, local history, and, where known, modification by man. MATERIALS AND METHODS.-Unbaited, unscreened 44 x 23 cm galvanized minnow traps (6.4 mm mesh) were placed at several sites in spring systems (except for Preston Town Spring) for a period of two hours in July 1983. Unscreened minnow traps baited with bread were used in November 1983 and March 1984. Underwater observations with face mask and snorkle were made during July in springs and their outflows (Preston Big, Lund Town, Hiko, Crystal, and Ash springs) to confirm species composition and alleviate trapping bias. Fishes in Preston Town Spring and the Moapa River at Home Ranch were collected with a 6.4 mm mesh, 2.7 x 1.2 m nylon minnow seine. All fishes captured during sampling were counted, recorded, and released. RESULTS.-White River Valley.-In 1880, the federal government granted some two million acres in eastern Nevada to the state. A policy was established whereby this land could be purchased by individuals at

Spawning Season of the Razorback Sucker, Xyrauchen texanus in Lake Mohave, Arizona and Nevada

1.25 per acre, with a 25¢ per acre downpayment. Buyers recognized that ownership of springs dictated land control so that when lands were sold, springs, and usually 16.2 ha immediately around them,were purchased first. When an individual completed paying for the land, he was granted a patent, or title, from Nevada; if, however, the individual defaulted on payment, the land reverted and could be resold. Through default by some landowners, a few individuals were able to acquire vast amounts of land along the upper course of the pluvial White River (Georgetta, 1972). Preston Big Spring.-This spring lies north of the town of Preston. Like other upper valley springs, it is cool (21.7°C) at the outflow. The area was first settled in the 1870s (see Preston Town Spring account below for other historical information). Vegetation in Preston Big Spring in 1983 remained the same as described by Miller and Hubbs (1960) and Williams and Wilde (1981). Fishes known to have occurred in this spring included White River spinedace (Lepidomeda albivallis), an undescribed subspecies of speckled dace (Rhinichtyhys osculus), White River desert sucker (Catostomus clarki intermedius), and Preston White River springfish (Crenichthys baileyi albivallis) (Williams and Wilde, 1981). Spinedace were in the outflow in the mid to late 1960s and afterwards (Fig. 2), but trapping, seining, electroshocking, and underwater observations indicated its disappearance shortly before 1980 (Deacon et al., 1980). We concur with Williams and Williams (1982) and Deacon and Williams (1984) that this species has been extirpated from this spring and its outflow. A second species appears to have been extirpated more recently. The White River desert sucker, which typically avoids minnow traps in Preston Big Spring (Fig. 2), was last collected at this locality by seining and electroshocking in July 1980 (Deacon et al., 1980). None was caught or observed in 1983, and we believe it also has been extirpated from this spring and its outflow. J. Hutchings (pers. comm. 1983) reported dead suckers in downstream irrigation structures in summer 1982, apparently killed by a heavy dose of copper sulfate. It is possible that applications of copper sulfate prior to 1980 also were responsible for extirpation of spinedace. November 1985 505 This content downloaded from 207.46.13.169 on Sat, 01 Oct 2016 06:03:55 UTC All use subject to http://about.jstor.org/terms PRESTON BIG SPRING L. albivallis ...R. osculus spp. -C. c. intermedius --C. b. albivallis