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The Sierra Nevada yellow‐legged frog (Rana sierrae) was once an abundant and widely distributed amphibian in California's alpine ranges. Rana sierrae is adapted to high‐elevation, fishless habitats. Its adaptions are reflected in a unique life cycle that involves a flexible, extended juvenile phase due to the short growing season typical of its alpine habitat. However, today this species is critically endangered, and most populations have been extirpated from their native range. Here, we present an 18‐yr‐long demographic study of a R. sierrae population in 15 lakes at Dusy Basin in Kings Canyon National Park. We focused on the period leading up to the arrival of the pathogenic chytrid fungus, Batrachochytrium dendrobatidis (Bd), and the subsequent local extinction of R. sierrae. We used N‐mixture abundance modeling, which accounts for detection probabilities, to quantify factors affecting frog abundance at different life stages. The abundance of subadult and adult frogs was negatively associated with the presence of introduced trout (Oncorhynchus mykiss and O. aquabonita). Frog abundance in all life stages was positively associated with lake surface area. The propensity of lakes drying correlated negatively with abundance of eggs, subadults, and adults in the following year. Moreover, drought years, characterized by longer summers and less winter snowpack, led to higher rates of lakes drying. Finally, our results suggest that the frequency of such droughts in the region has increased since 1937. Increased frequency or severity of droughts is expected to decrease the value of shallow lakes for Sierra Nevada yellow‐legged frogs because these habitats are prone to drying. We discuss our results in terms of future restoration strategies, including reintroduction and probiotic treatment, in this changed and changing ecosystem.

Pacific trout Oncorhynchus spp. in western North America are strongly valued in ecological, socioeconomic, and cultural views, and have been the subject of substantial research and conservation efforts. Despite this, the understanding of their evolutionary histories, overall diversity, and challenges to their conservation is incomplete. We review the state of knowledge on these important issues, focusing on Pacific trout in the genus Oncorhynchus. Although most research on salmonid fishes emphasizes Pacific salmon, we focus on Pacific trout because they share a common evolutionary history, and many taxa in western North America have not been formally described, particularly in the southern extent of their ranges. Research in recent decades has led to the revision of many hypotheses concerning the origin and diversification of Pacific trout throughout their range. Although there has been significant success at addressing past threats to Pacific trout, contemporary and future threats represented by nonnativ...

From 1997 to 2006, we used mark-recapture models to estimate the site fidelity of 1250 Sierra Nevada yellow- legged frogs (Rana sierrae) in Kings Canyon National Park, California, USA, during their three main activity periods of overwintering, breeding, and feeding. To quantify site fidelity, the tendency to return to and reuse previously occupied habitats, we used multistrata models (with water bodies as the strata) and potential function analyses. The probability of returning to previously used water bodies during all activity periods was typically greater than 80% and always greater than the probability of moving to other water bodies. Site fidelity models (with lake-specific movement transitions) were favored over those models that held movement transitions equal between lakes. Potential function analyses demonstrated that frogs were most strongly attracted to their original capture lakes rather than moving to the nearest available breeding or overwintering lake. Under current disturbances in high-elevation Sierra Nevada lakes (exotic trout, climate change), site fidelity is problematic because frogs return to lakes subject to drying or those with fish rather than dispersing to other lakes. Future recovery of declining species will need to focus efforts towards restoring habitats when animals maintain strong site fidelity even when their habitats deteriorate. Resume´ : De 1997 a 2006, des modeles de marquage-recapture nous ont servi a estimer la fideliteau site de 1 250 gre- nouilles a pattes jaunes de la Sierra Nevada (Rana sierrae) dans le parc national de King's Canyon, Californie, E ´ .-U., du- rant leur trois principales periodes d'activite ´, soit l'hivernage, la reproduction et l'alimentation. Afin de quantifier la fideliteau site, c'est-a `-dire la tendance a retourner dans des habitats utilises anterieurement et ales exploiter de nouveau, nous utilisons des modeles astrates multiples (les plans d'eau representant les strates) et des analyses fonctionnelles poten- tielles. La probabilitede retourner dans un plan d'eau dejautiliseest, dans l'ensemble des periodes d'activite ´ ,g enerale- ment de plus de 80 % et toujours plus elevee que la probabilitede se deplacer vers un autre plan d'eau. Nous preferons les modeles de fideliteau site avec des transitions de deplacement specifiques achaque lac aux modeles qui presupposent que les transitions de deplacement sont egales pour tous les lacs. Les analyses fonctionnelles potentielles montrent que les gre- nouilles sont beaucoup plus fortement attirees vers le lac de leur premiere capture que portees ase deplacer vers le lac le plus proche de reproduction ou d'hivernage. Dans les conditions actuelles de perturbations dans les lacs de haute altitude de la Sierra Nevada (truites exotiques, changement climatique), la fideliteau site pose des problemes parce que les gre- nouilles peuvent retourner ades lacs sujets a la dessiccation ou des lacs contenant des poissons, plutot que se disperser vers d'autres lacs. La recuperation future des especes en declin devra concentrer ses efforts sur la restauration des habitats lorsque les animaux conservent une forte fideliteau site meme quand leurs habitats se deteriorent. (Traduit par la Redaction)

We used skeletochronology to determine the ages of 149 (74 females, 44 males, and 31 juveniles) Mountain Yellow-legged Frogs (Rana muscosa) from 13 locations (elevation 1509–3501 m) throughout their current range in the Sierra Nevada mountains of California. Lines of arrested growth (LAGs) from excised toe bones were distinct in these high elevation frogs, and each LAG was assumed to represent one year of age. Females ranged in age from 0–10 years (mean = 4.1 years) and males from 0–8 years (mean = 4.0 years). The skeletochronological age was that of the post-metamorphic frog and did not include the tadpole stage. Mountain Yellow-legged Frogs spend 3–4 years as tadpoles, but no age markers are found in their cartilaginous skeletons; thus, their total age, if both tadpole and post-metamorphic stages were included, would range up to 14 years. Females were significantly longer (snout–vent length: SVL) than males and had greater mean mass, but there was no difference in the mean ages. Juvenile fr...

To determine the response of Mountain Yellow-Legged Frogs to short distance translocations, I placed transmitters on 20 adult frogs and moved them short distances from 144-630 m and monitored their responses for up to 30 days. Of the 20 translocated frogs, seven frogs returned to their original capture site, four frogs moved in the direction of their capture site but had not returned by the end of the study, and nine frogs did not return and were found at the translocation site. Apparently, displacing frogs was stressful, and translocated frogs lost body mass during the study period. Eighteen translocated frogs that were weighed at the beginning and end of the study lost body mass (mean loss was1.2 g) compared to a group of 18 randomly selected PIT tagged frogs also weighed during the same tracking period (mean gain in body mass 5 2.5 g) at our Kings Canyon study site. Translocation of adult Rana muscosa as a conservation tool may not be effective because some would simply attempt to return to their original capture site, and their homing may be stressful to an already declining frog population.

Human-caused fragmentation of habitats is threatening an increasing number of animal and plant species, making an understanding of the factors influencing patch occupancy ever more important. The overall goal of the current study was to develop probabilistic models of patch occupancy for the mountain yellow-legged frog (Rana mus- cosa). This once-common species has declined dramatically, at least in part as a result of habitat fragmentation resulting from the introduction of predatory fish. We first describe a model of frog patch occupancy developed using semiparametric logistic regression that is based on habitat characteristics, fish presence/absence, and a spatial location term (the latter to account for spatial autocorrelation in the data). This model had several limitations in- cluding being constrained in its use to only the study area. We therefore developed a more general model that incorporated spatial autocorrelation through the use of an autocovariate term that describes the degree of isolation from neighboring frog populations (autologistic model). After accounting for spatial autocorrelation in patch occupancy, both models in- dicated that the probability of frog presence was strongly influenced by lake depth, elevation, fish presence/absence, substrate characteristics, and the degree of lake isolation. Based on cross-validation procedures, both models provided good fits to the data, but the autologistic model was more useful in predicting patch occupancy by frogs. We conclude by describing a possible application of this model in assessing the likelihood of persistence by frog

Rising temperatures due to climate change are pushing the thermal limits of many species, but how climate warming interacts with other anthropogenic disturbances such as land use remains poorly understood. To understand the interactive effects of climate warming and livestock grazing on water temperature in three high elevation meadow streams in the Golden Trout Wilderness, California, we measured riparian vegetation and monitored water temperature in three meadow streams between 2008 and 2013, including two “resting” meadows and one meadow that is partially grazed. All three meadows have been subject to grazing by cattle and sheep since the 1800s and their streams are home to the imperiled California golden trout (Oncorhynchus mykiss aguabonita). In 1991, a livestock exclosure was constructed in one of the meadows (Mulkey), leaving a portion of stream ungrazed to minimize the negative effects of cattle. In 2001, cattle were removed completely from two other meadows (Big Whitney and Ramshaw), which have been in a “resting” state since that time. Inside the livestock exclosure in Mulkey, we found that riverbank vegetation was both larger and denser than outside the exclosure where cattle were present, resulting in more shaded waters and cooler maximal temperatures inside the exclosure. In addition, between meadows comparisons showed that water temperatures were cooler in the ungrazed meadows compared to the grazed area in the partially grazed meadow. Finally, we found that predicted temperatures under different global warming scenarios were likely to be higher in presence of livestock grazing. Our results highlight that land use can interact with climate change to worsen the local thermal conditions for taxa on the edge and that protecting riparian vegetation is likely to increase the resiliency of these ecosystems to climate change.

Mountain yellow-legged frogs (Rana muscosa) at high elevations of the Sierra Nevada must obtain enough food during summer to survive 7-9 winter months when their aquatic habitats are frozen and food is presumably unavailable. Adults of R. muscosa prey on a variety of organisms, including aquatic and terrestrial invertebrates and anuran larvae. To determine if anuran larvae influence the condition, distribution, and survival of adults of R. muscosa, we assessed body con- dition (variation from the expected mass for given length) and distribution of R. muscosa in relation to abundance and distribution of larval Hyla regilla, Bufo canorus, and Bufo boreas. Using three years of mark-recapture data, we found that abundance of larval H. regilla in a water body was positively correlated with the condition of R. muscosa. Moreover, R. muscosa had higher relative mass (W r) values in areas with other anuran larvae than in areas with no other amphibian species. High Wr values significantly increased the probability of recapturing frogs in following years. Using surveys of over 1700 lakes and ponds in the John Muir Wilderness and Kings Canyon National Park, we also found that the presence of larval H. regilla or Bufo in a water body was a significant indicator of the presence of adults of R. muscosa after accounting for significant habitat and isolation variables. These findings taken together suggest that some adults of R. muscosa actively seek out water bodies with other anuran species during the critical summer months and that the anuran larvae provide a nutritious food source that increases the body condition and, therefore, survival of the frogs.

We used analyses based on surveys of > 1700 water bodies in a 100,000-ha area in the John Muir Wilderness (JMW) and Kings Canyon National Park (KCNP) to determine the influence of nonnative trout on the distribution and abundance of Hyla regilla in the High Sierra Nevada. At the landscape scale (JMW compared to KCNP), a negative relationship between trout and frogs in lakes was evident. In the JMW study area where trout are more abundant, only 7.2% of all water bodies contained H. regilla versus 26.6% in the KCNP study area. Also, the percentage of the total water body surface area containing H. regilla was 19.4 times higher in the KCNP study area than in the JMW study area. Hyla regilla were most abundant in portions of KCNP where the probability of finding lakes with trout is lowest and least abundant in the northern part of the JMW where the probability of finding lakes with trout is highest. At the water body scale, after accounting for the effects of all significant habitat and isolation var...

Movement ecology and seasonal distribution of mountain yellow-legged frogs (Rana muscosa) in Dusy Basin (3470 m), Kings Canyon National Park, California, were characterized using passive integrated transponder (PIT) surveys and visual encounter surveys. We individually PIT-tagged 500 frogs during the summers of 1997 and 1998 and monitored these individuals during seven recapture surveys in 1997 and 15 recapture surveys in 1998 from the time they emerged from overwintering in July until the lakes froze for the winter in October. Probability of movement between lakes was associated with abundance of Hyla regilla larvae in the different lakes of origin, activity of the frogs (overwintering, breeding, feeding), and time of year. Overland movements exceeding 66 m were observed in 17% of the tagged frogs. Movement between lakes 1 km apart was detected. Site fidelity from 1997 to 1998 was high, and 97% of the tagged frogs recaptured in October of both years were found in the same overwintering lakes. Frogs were more narrowly distributed in spring and fall than in summer. Summer frog densities (number per meter of shoreline) were positively related to water temperature, air temperature, maximum lake depth, and presence of H. regilla larvae and negatively related to presence of trout. Mountain yellow-legged frogs use a range of aquatic sites throughout their activity period, and basins with a variety of deep lakes and shallow ponds may be the most appropriate reserves for this declining species.

One of the most puzzling aspects of the worldwide decline of amphibians is their disappearance from within protected areas. Because these areas are ostensib ly undisturbed, habitat alterations are generally perceived as unlikely causes. The introduction of non-native fishes into protected areas,however, is a common practice throughout the world and may exert an important influence on amphibian distributions. We quantified the role of introduced fishes (several species of trout) in the decline of the mountain yello w-legged-frog (Rana muscosa) in California's Sier ra Nevada through surveys of >1700 sites in two adjacent and historically fishless protected areas that dif fered primarily in the distribution of introduced fish. Negat ive effects of fishes on the distri bution of frogs we re evident at three spatial scales. At the l a n d s c ape scale, c o m p a risons between The two protected areas indicated that fish distri bution was stro n g ly n egat ive ly corre l at e d with the distribution of frogs. At the watershed scale, the percentage of total water-body surface area occupied by fishes was a highly significant predictor of the percenta ge of total water-body surface area occupied by fr ogs. At the scale (if individual water bodies, frogs were three times more likely to be found and six times more abundant in fishless than in fish-containing water bodies, after habitat effects were accounted for. The strong effect of introduced fishes on mountain yello w-legged frogs appears to result from the unique life history of this amphibian whic h frequently restricts larvae to deeper water bodies, the same habitats into which fishes have most frequently been introduced. Because fish populations in at least some Sierra Ne vada lakes can be remo ved with minimal effort, our results suggest that the decline of the mountain yellow-legged frog might be relatively easy to reverse.

Nearly all mountain lakes in the western United States were historically fishless, but most now contain introduced trout populations. As a result of the impacts of these introductions on ecosystem structure and func tion, there is increasing interest in restoring some lakes to a fishless condition. To date, however, the only effective method of fish eradication is the application of rotenone, a pesticide that is also toxic to nontar get native species. The objective of this study was to assess the effectiveness of intensi ve gill netting in eradicating the trout population from a small subalpine lake in the Sierra Ne vada, California. We remo ved the resident trout population and a second trout population acci dentally stocked into the study lake within 18 and 15 gill net sets, respectively. Adult trout were highly vulnerable to gill nets, but younger fish were not readily captured until they reached approximately 110 mm. To determine the utility of gill netting as a fish eradication technique in other Sierra Nevada lakes, we used morphometry data from 330 Sier ra Nevada lakes to determine what proportion had characteristics similar to the study lake (i.e., small, isolated lakes with little s p awning hab i t at). We estimated that gill netting would be a viable eradication method in 15-20% of the high mountain lakes in the Sierra Nevada. We conclude that although gill netting is likely to be more expensi ve and time consuming than rotenone application, it is a viable alternati ve under some conditions and should

Habitat use by rainbow trout Oncorhynchus mykiss is described for a southern California stream where the summer water temperatures typically exceed the lethal limits for trout (>25°C). During August 1994, water temperature, dissolved oxygen (DO), and trout distribution were monitored in two adjacent pools in Sespe Creek, Ventura County, where summer water temperature reached 28.9° C. Water temperature was an important factor in trout distribution in the two pools. During 1–11 August 1994, water temperatures in pool 1 ranged from 21.5°C at the bottom (4.1 m) to 28.9° C at the surface. After 5 August, trout were no longer found in this pool, suggesting that trout had moved out of the high temperature water or died. In the adjacent, shallower (1.5m) pool 2, surface water temperatures were as high as 27.9° C, but temperatures on the bottom remained cooler (17.5–21° C) than pool 1, presumably due to groundwater seeps. Consistent aggregations of trout were observed in pool 2 throughout the study period. During the day when water temperature was highest, most trout were found in a region of the pool with the lowest water temperature (mean=18.3° C). Conversely, regions with the highest water temperatures had the fewest trout during the day. The seeps may have introduced water with low dissolved oxygen into pool 2, as the DO in many locations on the bottom ranged from

Impacts of livestock grazing on California golden trout Oncorhynchus mvkiss aguabonita and their habitat were studied inside and outside of livestock exclosures in the Golden Trout Wilderness, California. In two consecutive years, the majority of stream physical characteristics showed large differences between grazed and ungrazed areas, and the directions of these differences were consistent with the recovery of exclosed streams and riparian areas from impacts caused by livestock grazing. Ungrazed areas consistently had greater canopy shading, stream depths, and bank-full heights and smaller stream widths than grazed areas. California golden trout were very abundant in the study sites; their densities and biomasses were among the highest ever recorded for stream-dwelling trout in the western United States. California golden trout density and biomass per unit area were significantly higher in ungrazed than in grazed areas in three of four comparisons. Differences between grazed and ungrazed areas ...

I used radio transmitters to determine habitat selection and movement patterns of California golden trout Oncorhynchus mykiss aguabonita in two areas defined by their different levels of habitat recovery in the Golden Trout Wilderness, California. Study areas were differentiated by the amount of streamside vegetation (low or high coverage of beaked sedge Carex rostrata). Lower amounts of streamside vegetation were typically associated with other signs of degradation caused by cattle, including widened streams, collapsed banks, and reduced bank undercutting. Twenty-nine California golden trout were monitored from 6 July to 14 July 1994 over 192 diel-tracking hours at six study sections in low- and high-sedge areas in Mulkey Meadow. In both low- and high-sedge areas, California golden trout were observed using nine habitat features (undercut bank, willows, collapsed bank, open channel, aquatic vegetation, sedge, boulder, grass, and detrital mats), but they more often selected undercut banks, aquati...

I used radio transmitters to determine the diel habitat use and movement patterns of California golden trout Oncorhynchus mykiss aquabonita inside and outside cattle exclosures on the South Fork Kern River, Golden Trout Wilderness, California. Twenty-three golden trout were monitored from September 10 to 19, 1993, during 216 diel-tracking hours at four study sites in upper and lower Ramshaw Meadow. No differences in distances moved or home ranges were detected between golden trout inside and outside exclosures. Mean home ranges were 18.5–54.0 m inside the two exclosure sites and 36.0–68.7 m outside the two exclosures. Most golden trout were found within 5 m of their previously recorded location at both upper (93.5% of 521 observations) and lower (92% of 394 observations) Ramshaw Meadow sites. Movement of individual fish varied: five fish moved less than 5 m throughout the 10-d study period, whereas 12 fish moved 100–608 m. Golden trout were active both day and night, and I observed them feeding t...

We documented temperature stratification in a deep bedrock pool in the North Fork of the American River, described the diel movement of rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta, and determined whether these trout used cooler portions of the pool. From July 30 to October 10, 1992, the main study pool and an adjacent pool were stratified (temperature differences between surface and bottom were as great as 4.5°C) on all but two days. Six rainbow and one brown trout equipped with temperature-sensitive radio transmitters used water with temperatures ranging from 12 to 19.3°C. During the late afternoon, when the widest range of water temperature was available, trout were found in temperatures up to 19.3°C even though cooler (14.5°C) water was available. Radio tracking indicated that fish were significantly more active and had significantly larger home ranges at night; fish were least active during the day. Because we found no evidence of subsurface seepage into the pool and water ...

We compared assemblages of demersal rockfishes (Scorpaenidae) associated with two areas of the continental slope off northern Vancouver Island, British Columbia, Canada. Twenty and 21 sets of sunken gill nets were completed on trawlable and untrawlable areas, respectively. The species assemblages on the two areas were markedly different, as demonstrated by their diversity, evenness, and percent similarity and by cluster analysis. On the trawlable area, the catch was numerically dominated by Pacific ocean perch Sebastes alutus (37.6%), splitnose rockfish S. diploproa (23.5%), greenstriped rockfish S. elongatus (12.7%), and bocaccio S. paucispinis (7.3%). This contrasted with the untrawlable area, where the catch was numerically dominated by sharpchin rockfish S. zacentrus (70.8%), and redbanded rockfish S. babcocki made up half (14.5%) the remaining catch. We found no evidence to support the claim by some fishermen that exploited rockfishes on trawlable areas, especially Pacific ocean perch, are m...

Ultrasonic telemetry was used to investigate the home ranges and homing routes of 11 copper, Sebastes caurinus, and quillback, Sebastes maliger, rockfishes. Home ranges of four copper and quillback rockfishes were monitored to determine if movement occurred during the day, night, or strong current (7.4 km/h). As expected from previous conventional tagging work, home ranges were small (most 2) on high relief reefs and considerably larger (within 4000 m2) on low relief reefs. No off-reef movement by copper and quillback rockfishes was detected on either reef type. To determine homing routes, the daily positions of seven copper and quillback rockfishes were monitored as they proceeded back to their home sites after experimental 500-m displacements from a high relief rocky reef to a low relief rocky reef. Six of the seven displaced copper and quillback rockfishes took from 8 to 25 days to return home; one quillback rockfish was followed for 16 days and lost, it was last located approximately halfway back to the original home site. Once displaced rockfish returned to their original capture site, no subsequent movement was detected, suggesting home site recognition. Homing seemed to consist of three phases: (i) initial movements along a bimodal northwest-southeast axis that are possibly associated with directional preferences in exploratory migrations, (ii) movement (westerly) towards the home reef, and (iii) the final location of the home site. Homing and exploratory migrations may be characteristic behaviors in the speciose rockfish group; the evolutionary advantage ensures rockfishes locate and utilize high quality habitats.

A study was designed to test whether habitat association affects the movement patterns and habitat preferences of copper, quillback, and brown rockfishes. Resighting of tagged rockfishes (512 tagged rockfishes and 726 resightings) from July 1986 through June 1988 indicated that home ranges, movements from reefs, and tendency to return from experimental displacement (up to 8.0 km) were significantly different on the three habitat types compared. On high relief rocky reefs, rockfishes maintained small home ranges (most within 30 m2) and displayed strong reef fidelity that was not affected by season; no off-reef movement was detected and rockfishes generally returned from displacements. On artificial reefs, rockfishes also maintained small home ranges (most within 30 m2), however, there were pronounced seasonal habitat preferences. In the summer, artificial reefs become less suitable; considerable off-reef movement occurred and rockfish did not return from displacements. In contrast, during fall and winter, rockfishes remained on artificial reefs and returned from displacements. On low relief rocky reefs, rockfishes maintained considerably larger home ranges (most within 400 m2 and some up to 1500 m2) and habitat use was strongly affected by season; rockfishes only inhabited low relief reefs in the summer and only returned from displacements in the summer coincident when peak algal cover. In addition, there was substantial movement between artificial reefs and adjacent low relief reefs; many rockfishes leave artificial reefs in the summer, move to low relief reefs, and return to artificial reefs in the fall when kelp disappears on low relief reefs. Through habitat assessment, movement in response to habitat quality, and ability to home, these rockfish maintain a flexible behavior for optimal habitat use.

The dramatic amphibian population declines reported worldwide likely have important effects on their predators. In the Sierra Nevada, where amphibian declines are well documented and some are closely tied to the introduction of nonnative trout, the mountain garter snake, Thamnophis elegans elegans, preys predominately on amphibians. We surveyed 2103 high-elevation lakes in the Sierra Nevada, quantified the distributional relationship between the mountain garter snake and anuran amphibians (Pseudacris regilla, Rana muscosa, and Bufo spp.) and used this information to evaluate the possibility that amphibian declines lead to declines of garter snakes. We observed a strong association between amphibian presence and garter snake presence. The probability of finding snakes in lakes with amphibians was 30 times greater than in lakes without amphibians. Lakes with snakes had higher numbers of amphibians within 1 km (mean = 4018.8) than did lakes without snakes (mean = 642.1). On a landscape scale, in Kin...

This paper reports on the response by amphibians, benthic macroinverte- brates, and zooplankton in naturally fishless alpine lakes to fish introductions and subsequent fish disappearance. We assessed resistance (the degree to which a system is altered when the environment changes) by comparing faunal distribution and abundance in lakes that have never been stocked with fish vs. the distribution and abundance in lakes that have been stocked and still contain fish. We assessed resilience (the degree and rate of a system's return to its previous configuration once the perturbation is removed) by comparing faunal distribution and abundance in lakes that were stocked at one time but have since reverted to a fishless condition (stocked-now-fishless lakes) vs. the distribution and abundance in lakes that have never been stocked. We quantified recovery rates and trajectories by com- paring faunal assemblages of stocked-now-fishless lakes that had been fishless for 5-10, 11-20, and .20 yr. Faunal assemblages in the study lakes had low resistance to fish introductions, but in general showed high resilience. The mountain yellow-legged frog (Rana muscosa), con- spicuous benthic macroinvertebrates, and large crustacean zooplankton (.1 mm) were dramatically reduced in distribution and abundance by fish introductions but generally recovered to predisturbance levels after fish disappearance. Inconspicuous benthic inver- tebrate taxa, small crustacean zooplankton (,1 mm), and rotiferan zooplankton (,0.2 mm) were either unaffected by fish or increased in the presence of fish. For both the benthic macroinvertebrate community and the zooplankton community as a whole, fish disappear- ance was followed by a steady change away from the configuration characteristic of fish- containing lakes and toward that of lakes that had never been stocked. Both communities remained markedly different from those in never-stocked lakes 5-10 yr after fish disap- pearance and converged on the configuration of never-stocked lakes only 11-20 yr after fish disappearance. Recovery was likely facilitated by the winged adult stages of many benthic macroin- vertebrates, resting eggs of zooplankton, and nearby source populations of frogs. However, many frog populations have disappeared since the time that lakes in this study reverted to a fishless condition, and the viability of zooplankton egg banks should decline in fish- containing lakes over time. As a result, faunal resilience may be lower in lakes that revert to a fishless condition today than is suggested by the results of our study. These findings have important implications for the restoration of alpine lake ecosystems.