RECOVERY PLAN FOR THE OWENS PUPFISH, CYPRINODON RADIOSUS Published by U.S. Fish ana Wildlife Service Portland, Oregon Approved: Regional Director, U.S. Fish and Wildlife Service 9Z, 7fy Date THIS IS THE COMPLETED RECOVERY PLAN OF THE OWENs PUPFISH. IT HAs BEEN APPROVED BY THE U.S. FISH AND WILDLIFE SERVICE. IT DOES NOT NECESSARILY REPREsENT OFFICIAL POSITIONS OR APPROVALS OF COOPERATING AGENCIES AND IT DOES NOT NECESSARILY REPRESENT THE VIEWS OF ALL INDIVIDUALS INVOLVED IN THE PLAN FORMULATION. THIS PLAN IS SUBJECT TO MODIFICATION AS DICTATED BY NEW FINDINGS AND CHANGES IN SPECIES STATUS AND COMPLETION OF TASKS DESCRIBED IN THE PLAN. GOALS AND OBJECTIVES WILL BE ATTAINED AND FUNDS EXPENDED CONTINGENT UPON APPROPRIATIONS, PRIORITIES AND OTHER BUDGETARY CONSTRAINTS. LITERATURE CITATION SHOULD READ AS FOLLOWS; U.S. FISH AND WILDLIFE SERVICE. 1984. RECOVERY PLAN FOR THE OWENS PUPFISH, CYPRINODON RADIOSUS. U.S. FISH AND WILDLIFE SERVICE, PORTLAND, OREGON. 47 pp. ADDITIONAL COPIES MAY BE OBTAINED FROM; FISH AND WILDLIFE REFERENCE SERVICE 1776 E. JEFFERSON STREET, FOURTH FLOOR ROCKVILLE, MARYLAND 20852 TELEPHONE; 1-800-582-3421 (IN MARYLAND; 1-301-468-1737) Acknowledgments The authors of this recovery plan are Thomas L. Taylor, California Department of Fish and Game (present address: California Department of Parks and Recreation, P.O. Box 2390, Sacramento, California 95811) and Jack E. Williams, U.S. Fish and Wildlife Service (2800 Cottage Way, Room E-1823, Sacramento, California 95825). We are greateful to the reviewers who provided technical assistance on earlier drafts of this plan. In particular, we wish to acknowledge Louis A. Courtois (California Department of Fish and Game, Sacramento), Larry L. Eng (California Department of Fish and Game, Sacramento), Gail C. Kobetich (U.S. Fish and Wildlife Service, Sacramento), Robert R. Miller (The University of Michigan, Ann Arbor), Peter B. Moyle (University of California, Davis), Edwin P. Pister (California Department of Fish and Guile, Bishop), Donald W. Sada (U.S. Fish and Wildlife Service, Reno), and Darrell M. Wong (California Department of Fish and Game, Bishop). Were it not for the tireless efforts of Edwin P. Pister and other members of the Desert Fishes Council, the Owens pupfish and its habitats would have vanished long ago. Cover Photograph: Fish Slough with White Mountains in the background. Photograph taken 30 March 1981 by Thomas L. Taylor. Owens Pupfish Recovery Plan Executive Summary 1. Point or condition when species can be considered recovered. Species can be considered recovered when five populations, each with a minimum overwintering population of SUU, have been establisned in five separate areas. The populations must have been free of threats for a period of five consecutive years with no foreseeable threats in the near future. 2. What must be done to reach recovery? Present populations need to be secured. Three new retugia need to be established and their habitats secured. 3. What specifically must be done to meet needs of #2? Habitat and populations will be secure When. I) exotic species are controlled or eliminated, 2) emergent vegetation is controlled, and 3) sufficient water quality is guaranteed. For new refugia, habitats must be secured, management plans snould be developed and implemented, and puptish should be introduced. 4. What management/maintenance needs nave been identified to keep tne species recovered? Management plans will be developed and implemented. A monitoring program is proposed. Also, public education and law enforcement progrems (including periodic review of applicable laws and regulations) are included. TABLE OF CONTENTS Page PART I. INTRODUCTION ........ 1 Taxonomy ........ 2 Description ........ 2 Ecology ........ 4 Historic Distribution and Decline . 6 Causes of Decline ........ 8 Current Status and Conservation Efforts ........ 9 PART II. RECOVERY ....... 16 Objectives ....... 16 Step-down Outline ....... 18 Narrative ....... 22 Literature Cited .......38 PART III. IMPLEMENTATION SCHEDULE ....... 41 APPENDIX ....... 47 List of Agencies Asked to Submit Review Comments. 47 OMENS PUPFISH RECOVERY PLAN PART I. INTRODUCTION The Oweris pupfish ( Cyprinodon radiosus) orginally ranged throughout much of the Owens Valley, California. They were once abundant in shallow marshy areas and springs along the Owens River from Fish Slough in Mono County to Owens Lake in Inyo County, but domestic and agricultral use of the springs and water diversions have eliminated most of the habitat of the Owens pupfish. The introduction of exotic predator and competitors has also contributed to the extirpation of populations. For 14 years the Owens pupfish was believed to be extinct, but in 1956 a small population was "discovered" in Fish Slough. The significance of this population was not realized until it was redi scovered in 1964. This small population has been the source for all Owens pupfish populations that subsequently have been reestablished and exist today (Miller and Pister 1971). The depl eted status of this species has been widely recognized in the governmental and scientific communities. The U.S. Fish and Wildlife Service listed the Owens pupfish as endangered in 1967 (Federal Register 32:400i). The State of California also lists this species as endangered (California Department of Fish and Game 1980) as does the American Fisheries Society (Deacon et al. 1979). 2 Taxonomy The Owens pupfish was orginally referred to as C. macularius (Kennedy 1916). This taxonomic identification was questioned when sufficient information was collected to indicate that pupfish in the Amargosa and Owens River drainages should be considered taxonomically distinct from those in the Colorado River system (Miller 1943). In 1948, Miller published his findings describing the Owens pupfish, _C. radiosus, as a new species endemic to the Owens Valley. The type locality for the Owens pupfisn is the northwest spring of Fish Slough (Miller 1946), which is currently within the Owens Valley Native Fish Sanctuary. Relationships of C. radiosus, are considered to ue closer to the ancestral form of 4prinodon (cf. macuiarius), which entered the Owens and Deatn Valley areas during the Pliocene, than with C. nevadensis or C. salinus (Miller 1981). Description The Owens pupfish is a small, deep-bodied fish with a laterally compressed shape. Maximum total length for this species is 60 mm (2 3/8 in) but most are typically 30 to 45 mm (11/4 to 1 3/4 in). i4prinodon radiosus closely resembles _C. _macularius _ _ _ _ except that they lack the spine-like projections on the circuli of the scales and the interspaces among the circuli possess prominent reticulations (Miller 1948). The structural scale pattern of C. radiosus is similar to that of C._ nevadensis and _C. _diabolis _ _ _ of the Amargosa River drainage as 3 well as C. salinus and C._ milleri of Death Valley. Cyprinodon radiosus differs from the pupfishes in the Amargosa and Death Valley regions by possessing a very anteriorly positioned dorsal fin (predorsal length averages 53.3% of SL 1 in males and 54.8% in females) a thickened first dorsal fin ray, a higher average number of dorsal (i = 11.1), anal (i =10.4), and pelvic (i = 6.9) fin rays; a much more slender head (averages 21.9% of SL), and a larger caudal peduncle (averages 28.6% of SL in males and 26.2% in females) (Miller 1948). The species is illustrated in Miller (1948:Plate IX), Moyle (1976.257) and Soltz and Naiman (1978:12-13). Owens pupfish, like other species of Cyprinodon, are sexually dichromatic. Adult males possess a blue color overlying an olive color dorsally and slate ventrally (Miller 1948). Lateral bars are deep purplish with some gold color among the posterior bars. Lower parts of the head are silver and blue. The dorsal and anal fins are blue with an orange-amber border. The caudal fin may or may not possess a terminal black band. Miller (1948) characterizes the color of females as deep olive with brown lateral blotches and vertical bars shade toward purplish. The fins are yellowish with pale margins on the dorsal and anal. An ocellus is present on the posterior portion of the dorsal fin in females. Breeding colors of the Owens pupfish are described in detail by Miller and Pister (1971). 1 Standard length (SL) is the distance from the tip of the snout to the end of the vertebral column. 4 Except for color differences, tne Owens puptisn exnibits little sexual dimorphism. However, Miller (1948) noted that males possessed a deeper body, head, and caudal peduncle than females. The caudal peduncle is longer in males and the fins, particularly the anal, are larger. Sexes exhibit little variation in other mensural characters. Ecology Male pupfish are larger than females and are territorial. The spawning season extends from April to October depending on weather conditions. Once the water temperature exceeds 2O°C, spawning begins. Males become territorial and bright blue in color when spawning. Males defend their territory from otner male pupfish as well as all other fish species. Females that enter a male's territory are courted. Eacn female can spawn a total of bi.) to 200 eggs per season, but rarely lays more than one or two eggs at a time (Barlow i961). The eggs are transparent, demersal, and approximately 2 mm in diameter. They hatch in about 7 to 10 days, depending on water temperature. In captivity, pupfish larvae are large enough to feed from the day of hatching on small food items the size of brine shrimp nauplii (Great- and Haycock 1971). In the wild, pupfish fry live along the shorelines where the warm water supports abundant quantities of food. The fish mature in 3 to 4 months, permitting one spawning prior to their first overwintering period. Runoff from winter and spring rains creates extensive shallow areas wnich provide excellent spawning and nursery habitat for the pupfish. 5 During spring, the size of the pupfish population increases dramatically as this habitat enlarges and warms (Brown 1971).