Contributions to the Biology of the Woundfin, Plagopterus Argentissimus (Pisces: Cyprinidae), an Endangered Species

Great Basin Naturalist

Volume 38 Number 4 Article 11

12-31-1978

Contributions to the biology of the woundfin, Plagopterus argentissimus (Pisces: Cyprinidae), an endangered species

Jeffrey N. Cross University of Nevada, Las Vegas

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Recommended Citation Cross, Jeffrey N. (1978) "Contributions to the biology of the woundfin, Plagopterus argentissimus (Pisces: Cyprinidae), an endangered species," Great Basin Naturalist: Vol. 38 : No. 4 , Article 11. Available at: https://scholarsarchive.byu.edu/gbn/vol38/iss4/11

This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. CONTRIBUTIONS TO THE BIOLOGY OF THE WOUNDFIN, PLAGOPTERUS ARGENTISSIMUS (PISCES: CYPRINIDAE), AN ENDANGERED SPECIES

Jeffrey N. Cross'

Abstract.— The woundfin is a small, streamlined, omnivorous cyprinid that is now limited to the Virgin River basin where it was collected in the mainstream and one tributary during the present study. The woundfin occurred most frequently in runs and over sand substrates and less frequently in riffles and over rock substrates. It was common over at least half of its original range within the Virgin River. It was uncommon in the lower mainstream due to habitat alterations and, presumably, predation by and competition with exotic species.

The woundfin belongs to a unique tribe into the Colorado River. The climate of the of cyprinids, the Plagopterini, that is char- Virgin River basin is arid to semiarid, with acterized by spinous modifications of the mild winters, hot summers, and high evapo- anterior dorsal and pelvic rays (Miller and ration rates. The river is characterized by Hubbs 1960). It is a small (<75 mm SL), widely variable discharges and high sedi- scaleless, torpedo-shaped fish with large ment loads. fins, pair of barbels on the lips, and re- a Methods duced eyes. Deacon and Minckley (unpubl. mans.) estimate the maximum age to be Fish were collected with tied nylon min- individuals probably four years, but most do now seines (3.0, 3.7, 4.6, and 6.1 m long by not exceed two years. 1.2 and 1.8 m deep with 3 and 6 mm mesh) At one time the woundfin probably in- between 21 June 1973 and 15 March 1975. the larger of the lower Col- habited streams Each station (Fig. 1) was sampled with orado River basin (Minckley 1973). It was three consecutive seine hauls within each (Ari- last collected in the Gila River basin habitat type (run, riffle, or pool). Fish were zona) in the 1890s (Miller and Hubbs 1960). maintained in 19 liter buckets until sam- It is now limited to the mainstream of the pling was completed and returned alive to Virgin River and one of its tributaries. The the streams. A few specimens were returned purpose of the present study was to deter- to the laboratory preserved in 10 percent mine the distribution, general ecology, and formalin. status of woundfin populations in the Virgin At each station the following data were River basin. collected: water temperature, conductivity, current velocity, stream width, depth of Study Area capture, average depth of the habitat, and length of the seine haul. The Virgin River heads in the Colorado Fish returned to the laboratory were left Plateau geologic province in southwestern in formalin five days, washed in water two Utah. It flows southwesterly into the Basin days, and stored in 65 percent ethanol. A and Range geologic province and empties sterioscopic dissecting microscope was used into Lake Mead 320 km from its source. to examine gut contents. Specimens are Prior to the construction of Hoover Dam housed in the Department of Biological Sci- (1935), the Virgin River discharged directly ences, University of Nevada, Las Vegas.

Fisheries Research Institute. College 'Department of Biological Sciences, University of Nevada, Las Vegas, Las Vegas, Nevada 89154. Present address: of Fisheries, University of Washington, Seattle, Washington 98105.

463 464 Great Basin Naturalist Vol. 38, No. 4

Results LaVerkin Creek and generally comprised less than 50 percent of the fish fauna. The woundfin was collected in the The woundfin occurred most frequently Riverside, mainstream Virgin River from in nms (75 percent of all collections), less Nevada, upstream to LaVerkin Springs frequently in riffles (20 percent), and occa- = Springs), Utah, and in the lower ( Virgin sionally in pools (5 percent). It was collect- reaches of LaVerkin Creek (Fig. 1). It was ed over sand (60 percent of all collections), the most abundant of the native species; rubble and cobble (30 percent), and mud 5,000 out of 10,822 native fish collected (10 percent) substrates. The mean depth of occurred in .33 were woundfin. Woundfin capture was 43 cm (SE=13.3, n = 38); the percent of the collections in the lower average depth of the water was 25 cm Mesquite, mainstream (downstream from (SE = 6.2, n = 38). In one-half of the collec- Nevada) and made up from 30 to 100 per- tions, woundfin were associated with some cent of the catch but averaged less than 50 type of cover, usually overhanging deadfalls, percent. In the middle reaches of the brush, or trees. Water temperatures ranged mainstream (downstream from Hurricane, from 10.0 to 35.5 C with a mean of 23.7 C Utah) the woundfin was present in 90 per- (SE = 2.3, n = 38). Conductivities ranged cent of the collections and generally com- from 150 to 2650 /xmhos (at 25 C) with a prised 50 percent of the catch. In the upper mean of about 1100 /xmhos. Current veloci- mainstream it occurred in 65 percent of the ties ranged from zero to 1.13 m/sec with a collections and averaged less than 33 per- mean of 0.42 m/sec (SE = 0.09, n = 38). In cent of the catch. The woundfin was pres- more than 60 percent of the collections ent in all collections in the lower reaches of woundfin occurred in habitats that were

STATION RESERVOIR

. 30 . 1.0 2.0 I Q KILOMETERS ^ J / f

114°00 - ( 113°00 «

Fig. 1. Map of the Virgin River showing collection localities: (1) Riverside, Nevada; (2) Mesquite, Nevada; (3)

Littlefield, Arizona; (4) Arizona Narrows, Arizona; (5) St. George, Utah; (6) Hurricane, Utah; (7) LaVerkin

Springs, Utah; (8) LaVerkin Creek, Utah. December 1978 Cross: Woundfin Biology 465 considered to be physically unmodified; in visual selection of food. Soon after dried the remaining collections it occurred in foods were introduced into the aquaria, habitats considered to be moderately to woundfin began milling excitedly over the largely modified (irrigation withdrawals and bottom. Within one month most individuals return flows, organic wastes, stream chan- had begun rising to the surface to feed. nelization). Native fishes (Table 1) comprised an average of 89 percent (SE = 7.1, Discussion n = 38) of collections containing the woundfin. Distribution.— Within the Virgin River spawning habitat The and reproductive system the woundfin is limited in its up- behavior of the woundfin are not known. stream distribution by the highly saline La- Ripe, tuberculated individuals were collect- Verkin Springs (conductivity approximately ed in May. Spawning appeared to com- 15,000 ju,mhos at 25 C), which enter the riv- mence about April to May and continued er along the Hurricane Fault east of LaVer- through August (Lockhart, unpubl. mans.). kin, Utah (Fig. 1). Absence of the woundfin Young-of-the-year were collected from early from the river upstream from the springs June to mid-August. Juvenile woundfin oc- may be due to the order of appearance of cupied shallow areas lateral to the main the woundfin in the Virgin River and crus- current. When water levels were low, juve- tal movement along the Hurricane Fault. nile woundfin often occurred in the main Uplift of the Unikaret Plateau (part of the channel. North Rim of the Grand Canyon bounded Woundfin possess a poorly defined stom- on the west by the Hurricane Fault) during ach occupying about one-fifth of the total the Pliocene to Pleistocene could have led gut length. Examination of 14 specimens to the emergence of LaVerkin Springs collected in August partly at Littlefield and (Cook 1960, McKee et al. 1967). Sub- partly at the mouth of LaVerkin Creek pro- sequently, the Virgin River may have been duced the following items (in order of abun- invaded by the woundfin, a lower Colorado dance): sand grains, aquatic insect larvae River basin endemic; its upstream pene- (predominantly dipterans), filamentous green tration was limited by LaVerkin Springs. algae, plant debris, terrestrial insects The Virgin River roundtail chub is also lim- (mainly ants) and amphipod larvae. ited in its upstream distribution by LaVer- In laboratory aquaria (39 and 208 liters), kin Springs (Cross 1978). woundfin initially exhibited no evidence for Occurrence of the woundfin in only one

Table 1. Phylogenetic listing of the fish fauna of the Virgin River and their general distribution. M = mainstream, T = tributary, H = headwater, N = native species.

Family 466 Great Basin Naturalist Vol. 38, No. 4

tributary is probably related to a com- slightly less than imity) would seem to pre- bination of physical and chemical factors clude a predominantly algal-detrital diet. It unique among mainstream tributaries to La- may be that bacteria, protozoans, and mi- Verkin Creek. The creek originates as saline croalgae adsorbed to algae and detrital par- springs (conductivity approximately 1,200 ticles supply the nutrients or aid in the jumhos at 25 C), has a sand substrate, and is breakdown of plant material as in the mul- highly turbid. LaVerkin Creek is thus phys- let, Mtigil cephahis (Odum 1968, 1970). ically and chemically more similar to the Changes in Abundance.— Collections mainstream than to the other tributaries. and fieldnotes examined at Brigham Young Ash Creek, which enters the Virgin River University, the University of Michigan, the within 30 m of LaVerkin Creek, is fed by University of Nevada, Las Vegas, and the upstream runoff (conductivity about 200 U.S. National Museum indicate that wound- jumhos at 25 C) and is generally cooler and fin abundance in the mainstream Virgin less turbid than LaVerkin Creek. No River upstream from Mesquite Nevada, has woundfin were collected in Ash Creek dur- not appreciably changed since at least the ing the study. 1930s (few earlier records exist). Woundfin Reproduction.— The stimuli that initiate populations downstream from Mesquite the reproductive cycle of the woundfin are have, however, declined. The extirpation of not known. Spawning may be initiated by the woundfin from the Salt and Gila rivers low, clear water; juvenile woundfin first ap- in Arizona was attributed to drought, agri- pear coincident with the period of lowest cultural operations, water storage and diver- river discharge. Avoidance of high spring sion, and the introduction of exotic species discharges and turbidities would be advanta- (Miller and Hubbs 1960, Minckley and Dea- geous because eggs spawned at that time con 1968). These factors operate, to a great- would likely be carried away by the current er or lesser extent, within the Virgin River or buried in silt (there is almost no sub- basin. mergent or emergent vegetation in the Seasonal drying of extensive reaches of mainstream to which eggs could be affixed). the mainstream has reduced the habitable During the summer the Virgin River was range of the woundfin. Drying of the river often dry through the Arizona Narrows during low discharge periods undoubtedly (Fig. 1). Springs emerging above Littlefield occurred naturally, although probably in- accounted for the entire river flow down- frequently, before irrigation became widely stream. Two distinct sizes of young-of-the- used. At present the agricultural demand for year woundfin were present in the shallow water regularly results in dry reaches of riv- springs during late summer: a mode about er downstream from Hurricane, Utah, 10 mm and another about 25 mm. Appar- through the Arizona Narrows and down- ently adult woundfin had moved into the stream from Mesquite, Nevada, to Lake spring area to spawn, probably in response Mead during the summer. Reduction of to the low, clear water. available habitat was thought to be the pri- Lockhart (unpubl. ms.) noted that young- mary factor accounting for the decline of of-the-year woundfin exhibited growth Virgin River roundtail chub populations through October. October to December ap- (Cross 1978). peared to be the period of highest mortality Introduced species have also contributed for all woundfin, coinciding with minimum to the decline of woundfin populations in water temperatures and reduced food avail- the lower river via predation and, presum- ability. ably, competition. Predation on the native Food Habits.— From the small sample of species by exotics was facilitated by the cre- fish examined, woundfin appear to be omni- ation of Lake Mead and subsequent in- vorous. The temporal variability of the Vir- troductions of fish into the lake. Potential gin River would place a premium on gener- predators on the woundfin, including large- alized or opportunistic feeding habits. The mouth black bass, bluegill and green sun- relative shortness of the gut (intestine fish, black bullheads, and mosquitofish, are length/standard length [Odum 1970] is present in the lower river mainly as sea- December 1978 Cross: Woundfin Biology 467

sonal (summer and fall) emigrants from abundance has declined. A similar correla- Lake Mead.- Examination of the stomachs tion between an increase in abundance of of two largemouth black bass (118 and 167 the red shiner and the disappearance of the mm SL) from August collections revealed native cyprinids Meda fulgida and Tiaroga one imidentifiable fish in the first and a 50 cobitis was observed in the Gila River basin mm woundfin in the second. in Arizona (Minckley and Deacon 1968, Competition is more difficult to prove Minckley 1973). and only circumstantial evidence exists for The woundfin presently persists over at competition between the red shiner, a least half of its original range within the small, omnivorous cyprinid, and the wound- Virgin River basin. The precarious nature of

fin. Downstream from Mesquite, woundfin its existence has prompted its inclusion in abundance decreased while red shiner abvm- the U.S. Bureau of Sport Fisheries and dance increased. At Station 1 (Fig. 1) the Wildlife (1973) listing of endangered spe- red shiner regularly comprised 90 percent cies. The continued existence of the wound-

or more of the fauna; at Station 2 it aver- fin in the Virgin River basin is directly aged about 40 percent of the fauna; and at linked to the amount of further physical, Station 3 it was captured infrequently. This chemical, and biological alterations of the situation could have resulted from a deterio- mainstream habitat. ration of the habitat beyond the tolerance range of the woundfin, but not beyond that of the red shiner. The red shiner is capable Acknowledgments of withstanding intermittence, high temperatures, and high turbidities (Koster 1957, The following participated in various as- Cross 1967). Within its native range (mid- pects of the fieldwork, and their assistance western United States) the red shiner rarely is gratefully acknowledged: H. A. Berry, P. Calos, becomes abundant in clear streams with J. C. D. Deacon, J. E. Deacon, G. C.

constant discharge and large populations of Faber, J. Lockhart, and L. Loetterle. Access other cyprinids, but it increases rapidly in to museum collections was made possible abundance when drought decreases stream- by: Dr. R. R. Miller (University of Michigan flow and alters the composition of the fauna Museum of Zoology); Dr. W. W. Tanner (Cross 1967). (Brigham Young University); Dr. E. A. Alternatively, the decline of the woundfin Lachner (U.S. National Museum); and Dr. may have been a result of competition with W. L. Minckley (Arizona State University).

the red shiner. The woundfin is also par- The figure was prepared by Jan Shines. A to E. ticularly well adapted to the extreme fluc- special acknowledgment goes J. Dea- tuations in discharge, suspended sediment, con, my major professor, for his ideas and and temperature. It commonly occurred in encouragement during the study. habitat unsuitable for the other native species due to high temperatures (the LD^ for woundfin acclimated at 21.5 C was 34.5 C (Lockhart, unpubl. mans.), minimal river Literature Cited flow, or organic pollution. The scarcity of Cook, E. F. 1960. Geologic atlas of Utah: Washington woundfin in the lower river is not likely at- County. Utah Geol. .Mineral. Surv., Bull. 70. tributable to the poor quality of the habi- Cross, F. B. 1967. Handbook of fishes of Kansas. Misc. tat—comparable conditions occur upstream Publ. Mus. Nat. Hist. Univ. Kans. 45:l-.357. Cross, N. 1978. Status and ecologv- of the Virgin from the Arizona Narrows where woundfin J. River roundtail chub Gila robu.sta seminuda are frequently the only species collected. (Osteichthves: Cyprinidae). Southwest. Nat. What is more probable is that as a result of 23:519-528. E., W. L. Minckley. A review of in- the presence of the red shiner, woundfin Deacon, J. and

limited the upstream penetration of 'Few introduced fish persist in the river through the spring highwater period. Consequently, annual flooding has fishes were collected with- introduced species; the farthest upstream penetration recorded during the study was 100 km. The majority of the introduced in 70 km of Lake Mead. 468 Great Basin Naturalist Vol. 38, No. 4

formation on the woundfin, Plagopterus argen- rado River system. Misc. Publ. Mus. Zool. Univ. tissimus Cope. University of Nevada, Las Vegas. Mich. 115:1-39. Unpublished manuscript. Minckley, W. L. 1973. Fishes of Arizona. Arizona HuBBS, C. L. 1954. EstabUshment of a forage fish, the Game Fish Dept., Tucson. shiner (Notropis lutrensis), E. 1968. South- red in the lower Col- Minckley, W. L., and J. Deacon. orado River system. Calif. Fish Game western fishes and the enigma of "Endangered 40:287-294. species." Science 159:1424-1432. ecological significance of fine KosTER, W. J. 1957. Guide to the fishes of New Mexi- Odum, W. E. 1968. The co. Univ. New Mexico Press, Albuquerque. particle selection by the striped mullet Mugil Research ar- cephalus. Limnol. Oceanogr. 13:92-97. LocKHART, J. conducted on Plagopterus gentissimus. University of Nevada, Las Vegs. 1970. Utilization of the direct grazing and Unpublished manuscript. plant detritus food chains by the striped mullet

D., R. F. S. cephalus, 222-240. In: H. Steele McKee, E. Wilson, W. J. Breed, and C. Mugil p. ]. Breed. 1967. Evolution of the Colorado River (ed.). Marine food chains. Univ. Calif. Press, in Arizona. Mus. North. Ariz., Flagstaff, Bull. Berkeley. 44. U.S. Bureau of Sport Fisheries and Wildlife. 1973. Miller, R. R., and C. L. Hubbs. 1960. The spiny- Threatened wildlife of the United States. But. rayed cyprinid fishes (Plagopterini) of the Colo- Sport Fish. Wildl. Res. Publ. 114.