What can be done to reverse the decline of the mountain yellow-legged frog? Given that Rana muscosa and Rana sierrae are being impacted by at least two factors, the answer to this question is more complicated than believed just a few years ago. However, results from recent research indicate that removal of nonnative trout from key locations remains the most important conservation measure.
Current Conservation Efforts
Using the results from extensive amphibian and fish surveys and fish removal experiments (see Threats > Introduced Fish page for details), biologists in Sequoia-Kings Canyon and Yosemite National Parks, and from the California Department of Fish and Game (CDFG) are developing amphibian restoration plans and implementing fish removal projects (using gill nets and electrofishers) designed to conserve particularly important mountain yellow-legged frog populations (e.g., SEKI EA 2001; DFG Big Pine Plan 2005). These projects have already been remarkably successful (e.g., Knapp et al. 2007), increasing the total population size of R. muscosa and R. sierrae by tens of thousands of animals. Based on this success, Sequoia-Kings Canyon National Park is currently planning more extensive fish eradication efforts (SEKI Planning Update 2008). To date, much less conservation attention has been focused on the Transverse Ranges, but the CDFG is removing trout from a short section of stream in southern California in an effort to expand one of the last remaining R. muscosa populations in that area.
In addition to these conservation projects that are targeted at specific mountain yellow-legged frog populations, the CDFG is also beginning to make some important changes to its fish stocking program that are aimed at reducing the impacts of this program to amphibians in general. Under the revised program, stocking would occur only where (1) surveys for amphibians and fish have been completed, (2) stocking serves a valid fishery management purpose (e.g., no stocking of self-sustaining fisheries; Armstrong and Knapp 2004), and (3) sensitive amphibian species do not occur. These guidelines have led to significant reductions in the number of lakes being stocked, but have been only partially implemented. In 2007, environmental groups sued the CDFG over their fish stocking practices. The judge sided with the plaintiffs and required that the CDFG prepare an Environmental Impact Report (EIR) detailing the impacts of the fish stocking program. The draft EIR is expected in late 2008.
But what about impacts caused by chytridiomycosis?
A commonly-voiced concern is that fish removal efforts may amount to nothing over the long-term if the amphibian chytrid fungus (Batrachochytrium dendrobatidis) continues to spread through the range of the mountain yellow-legged frog. Given the extraordinary virulence of B. dendrobatidis, this is a reasonable concern. The overarching goal of mountain yellow-legged frog conservation must be to manage frog populations such that they are as resilient to natural and human-caused stressors as possible. Removing nonnative trout creates larger frog populations that are better connected with those in adjacent habitats (Knapp et al. 2007, Figure 1). These restored populations should be considerably more resilient to a wide variety of impacts, including disease.
Current fish removal projects have targeted a small number of lakes within each of several watersheds. These projects have been very successful, but the targeted watersheds remain dominated by fish populations. Given the importance of B. dendrobatidis in the decline of the mountain yellow-legged frog, it is more important than ever to return some entire watersheds to a fishless condition. Doing so will allow the development of frog populations at sites characterized by a wide variety of elevations, water temperatures, and habitat conditions, and some combination of these environmental conditions may well allow the persistence of frog populations despite B. dendrobatidis outbreaks.
How will frog conservation efforts affect the trout fishery?
Some anglers are understandably concerned that fish removal efforts aimed at restoring mountain yellow-legged frog populations will unduly impact trout fisheries in the Sierra Nevada. Given the ongoing and planned removal of trout populations, these impacts are undeniable but limited in scope. Even with the most ambitious fish removal program, trout fisheries will continue to exist in the majority of the thousands of lakes, streams, and rivers scattered across the Sierra Nevada. With careful planning, impacts to popular fisheries could be avoided and the quality of some fisheries could even be improved (Armstrong and Knapp 2004).
The question remains: Can we, as a society, work together to return some of the thousands of lakes and streams in the Sierra Nevada and Transverse Ranges to their natural fishless condition to preserve a frog that has been on this Earth for millions of years? Or will we hold onto the notion that fishless habitats are "barren", serving little or no purpose to the human visitor? In the answer to that question lies the fate of the mountain yellow-legged frog. I, for one, remain hopeful.