Basin‐wide Native Non‐game Fish Assessment 2011 Annual Report Revised on February 21, 2013 USDA Forest Service, Lake Tahoe Basin Management Unit Written by Christopher Lemmers (Biological Science Technician) and Maura Santora (Aquatic Biologist) Reviewed by Sarah Muskopf (Acting Forest Aquatic Biologist) and Shana Gross (Forest Ecologist) Approved by Holly Eddinger (Biological Program Leader) Original Version: April 19, 2012 Revised Version: February 21, 2013 1 TABLE OF CONTENTS Summary ....................................................................................................................................................... 2 Introduction .................................................................................................................................................. 3 Methods ........................................................................................................................................................ 5 Results ........................................................................................................................................................... 7 Discussion ................................................................................................................................................... 11 Recommendations ...................................................................................................................................... 13 Works Cited ................................................................................................................................................. 14 Appendix ..................................................................................................................................................... 17 Summary The Lake Tahoe Basin Management Unit (LTBMU) is conducting a fish assessment survey on state and federal lands within the basin to determine species presence, distribution, and relative abundance. These baseline conditions will provide information for future watershed and ecosystem level management decisions. To date 26 streams within the Lake Tahoe basin have been surveyed. In 2011, the Lake Tahoe Basin Management Unit aquatics field crew, with help from partner agencies, surveyed the Upper Truckee River (UTR) from the mouth at Lake Tahoe upstream 19.3 kilometers. Over 12,500 fish were sampled, 53 non‐native warm water fish were removed, and an estimated 330 invasive crayfish (Pacifastacus leniusculus) and 1,589 native western pearlshell mussels (Margaritifera falcata) were counted. Of the 12 species found, seven native species were documented: Lahontan redside (Richardsonius egregious), speckled dace (Rhinichthys osculus), Tahoe sucker (Catostomus tahoensis), mountain sucker (Catostomus platyrhynchus), Paiute sculpin (Cottus beldingi), mountain whitefish (Prosopium williamsoni), and Lahontan cutthroat trout (Oncorhynchus clarki henshawi). With the exception of speckled dace and Paiute sculpin, native fish species were a small percentage of fish sampled while non‐native brown and rainbow trout accounted for nearly 25% of the total fish sampled. In general, native species were limited in distribution and relative abundance, with the greatest species diversity found in the lower reaches of the UTR. 2 Introduction Historically, eight fish taxa were known to be native to the Lake Tahoe Basin including: Lahontan redside shiner (Richardsonius egregious), speckled dace (Rhinichthys osculus), Paiute sculpin (Cottus beldingi), Tahoe sucker (Catostomus tahoensis), mountain sucker (Catostomus platyrhynchus), Lahontan tui chub (Gila bicolor pectinifer), mountain whitefish (Prosopium williamsoni), and Lahontan cutthroat trout (Oncorhynchus clarki henshawi) (Miller 1951, Frantz and Cordone 1970, and Vander Zanden et al. 2003). Lake Tahoe’s fishery pre‐1900 was dominated by a single predator, the Lahontan cutthroat trout (LCT). Mountain whitefish and LCT were abundant and provided ample food for the Native Americans living around Lake Tahoe. LCT were extirpated from Lake Tahoe by 1939 (Cordone and Frantz 1968, Moyle 2002), and the population of mountain whitefish now occur in very low numbers (Murphy and Knopp 2000). Several factors have contributed to the decline or extinction of native fish and the degradation of fish habitat in the Lake Tahoe Region. Over‐fishing, logging, mining, dams, water diversions, intense grazing, road building, urban development, and the introduction of non‐native fish and other aquatic organisms are believed to have cumulatively contributed to the change in Lake Tahoe’s fish composition and degradation of fish habitat (SNEP 1996, Murphy and Knopp 2000, Cordone and Frantz 1968, Moyle 2002). In aquatic ecosystems modified by human disturbance, non‐native fish species often become dominant and out‐ compete native fish species (Deacon and Minckley 1974; Shepard et al. 1997; Brandenburg and Gido 1999; Schindler 2000; Knapp et al. 2001). During the last 130 years, numerous non‐native species have been introduced intentionally and unintentionally to the Tahoe Basin, altering its biological assemblage. The first series of introductions included nine species of salmonids thought to be suited to Tahoe’s environment. Only rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), lake trout (Salvelinus namaycush), brook trout (Salvelinus fontinalis), and kokanee salmon (Oncorhynchus nerka) survived and persist in the basin today. Non‐native salmonids, which dominate streams within the Lake Tahoe basin, have adverse effects on the distribution and abundance of native species in Sierra Nevada streams (Moyle and Vondracek 1985; Moyle and Williams 1990). Non‐native warm water fish have also been introduced into Lake Tahoe streams and near shore environment, including: brown bullhead (Ameiurus nebulosus), bluegill (Lepomis macrochirus), largemouth bass (Micropterus salmoides), smallmouth bass (Micropterus dolomieu), black crappie (Pomoxis nigromaculatus), and goldfish (Carassius auratus) (Basinwide Native Non‐ game Fish Assessment 2007‐2010; Kamerath et al. 2008). With the illegal introduction of non‐ native warm water fish and other aquatic species, such as signal crayfish (Pacifastacus leniusculus), the aquatic food web has drastically changed. These changes have been negatively correlated with the percent of native fish present (MacRae and Jackson 2001; Betolli et al. 1992; Vander Zanden et al. 2003; Moyle and Nickols 1973; Findlay et al. 2000). 3 Although several of Lake Tahoe’s tributary streams are still known to contain native fish, information about the historical and current status of native non‐game fish communities in the Lake Tahoe basin was almost non‐existent before this survey. The most recent comprehensive document about fisheries was compiled by the Tahoe Regional Planning Agency (TRPA) and U.S. Forest Service (USFS) in 1971 called “Fisheries of the Lake Tahoe and its Tributary Waters” (TRPA 1971). However, most of the information pertained to sport fisheries, while information pertaining to native non‐game species was presumed in most cases. This lack of current native species status and distribution triggered the initiation of the Basin‐wide Native Non‐game Fish Assessment (referred to as Fish Assessment) in 2007. Most inlet streams on the west and north shore of Lake Tahoe have been surveyed in the Fish Assessment. More recently, surveys have focused on the south shore of Lake Tahoe and in perennial streams where LTBMU projects are being planned. Originally, field crews were trained to record only the fish species found, but in 2011 two other aquatic species were noted when detected: Western pearlshell mussel (Margaritifera falcata) and signal crayfish. Western pearlshell mussel will likely be listed on the next update of the USFS Region 5 Sensitive Species List, which is currently in review. Also, local river restoration activities have started relocating current populations when old channel sections are be dewatered. Signal crayfish are a non‐ native aquatic species which alter the aquatic ecosystem by preying on fish and other native aquatic dependent species. Western pearlshell mussel is a freshwater mussel native to western North America. The mussels are long‐lived species (individuals may live for ~100 years) (Bauer 1992, Hastie et al. 2000a, b). Like most freshwater mussels, Western pearshell mussel has an obligate parasitic larval stage on fishes. After completing larval development, juvenile mussels drop from their fish hosts onto the river bed and become minute (~60‐μm) free‐living bivalves. Many historical populations throughout its range appear to have been severely reduced in size from dense beds to a few isolated individuals in flow refugia at many historical sites (Vannote and Minshall 1982, Hovingh 2004, Strayer et al. 2004, Howard 2008, 2010). In recent years, it was discovered that the Upper Truckee River (UTR) is home to one of the only known populations of Western pearshell mussel in the Lake Tahoe Basin. However, the extent and distribution of this species in the UTR and other streams in the Tahoe Basin is not well documented. Currently, this species is only known to occur in the lower and middle reaches of the UTR. Signal crayfish is a crustacean from the Columbia River, Oregon, and were introduced into Lake Tahoe in 1916 by California Department of Fish and Game (CDFG) officials (Riegel, 1959) and have spread from the lake into its tributaries. While their ecology has been studied in Lake Tahoe and nearby Donner Lake (e.g.