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The Effects of a Dam on Breeding Habitat and Egg Survival of the Foothill Yellow-legged Frog (Rana boylii) in Northwestern California
Abstract and Figures
Although the debate continues on the relative roles of natural fluctuations and anthropogenic influences in recently observed amphibian population declines (Blaustein 1994; McCoy 1994; Pechman et al. 1991; Pechman and Wilbur 1994; Travis 1994), many species are clearly demonstrating local extinctions and large-scale declines (Blaustein and Wake 1990; Blaustein et al. 1994b; Fellers and Drost 1993; Hayes and Jennings 1986; Jennings 1988). Causes of these declines can be placed in two broad categories: direct habitat degradation (Blaustein et al. 1994b), and more nebu-lous large-scale environmental changes and contamination (e.g., airborne pollutants, acid precipitation, ultraviolet radiation) (Blaustein et al. 1994a; Dunson and Wyman 1992; Fellers and Drost 1993; Hagstrom 1977; Harte and Hoffman 1989). Dams and water diversion projects have been proposed as causes of declines of many native frogs (Hayes and Jennings 1986; Jennings 1988;Moyle 1973), but the effects of these projects have not been quantitatively evaluated. Water diversions also have been implicated in region-wide declines of anadromous fish in the Pa-cific Northwest (Moyle and Williams 1990; Nehlsen et al. 1991) and are documented to adversely affect riverine macroinvertebrates (Petts 1984). Impacts to fish include loss and degradation of habitat because of reservoir filling and downstream changes in river morphology along with detrimental off-season andfluctuatingwaterreleases(BurtandMundie 1986; Petts 1984). A recent petition to list the arroyo southwestern toad (Bufo microscaphus califomicus) as endangered indicated that impound-ments associated with dam construction have caused a 40% loss in the original habitat of this toad. In addition, it was suggested that habitat quality downstream of dams has been severely com-promised by changes hi water temperatures, riparian vegetation, and habitat stability (Federal Register 1993). Our study provides information on both direct and indirect effects of a dam on the foothill yellow-legged frog (Rana boylii) in a northwestern Cali-fornia river system. Rana boylii is generally found in association with stream riffles that have rocky substrates and partly shaded banks (Hayes and Jennings 1988; Moyle 1973; Zweifel 1955). This frog ranges from northern Baja California, Mexico (Loomis 1965) to central Or-egon, west of the Sierra Nevada and Cascade crests. Rana boylii is currently listed as a Species of Special Concern in California (Laudenslayer et al. 1991) and is also a candidate for Federal list-ing (Federal Register 1994). The most notable declines are in southern California and the west slope drainages of the Sierra Nevada and southern Cascade Mountains (Jennings and Hayes 1994; Leonard et al. 1993). Our objectives were: (1) to describe the changes in Rana boylii breeding habitat in a dammed river prior to and some years fol-lowing dam construction, and (2) to document the effects of the timing of water releases from the dam on the reproductive ecol-ogy of this population. Our study took place on the main stem of the Trinity River, in Trinity County, California, USA, and covered the 63 km of river from Lewiston Dam (near Lewiston, California) downstream to the confluence with the North Fork Trinity, near Helena, Califor-nia (elevation 420-550 m). Construction of two dams, an upper (Trinity) and a lower (Lewiston), was completed in 1963. At Hel-ena, this river drains an area of 2968 km 2 . Before dam construc-tion the river had an average yearly (water year, Oct-Sept) dis-charge of 1.2 million acre-feet at Lewiston. During the four years of our study, the yearly discharge ranged from 270,800 to 367,600 acre-feet at Lewiston. The basin surrounding our study reach is 52% public land (USDA Forest Service and USDI Bureau of Land Management) and 48% privately owned. Land use activities within this watershed include logging and associated road building, rec-reation, and widely scattered home construction. Portions of river channel and adjacent areas were mined in the early to mid-1900's. Since 1984, the USDI Fish and Wildlife Service, in coopera-tion with the USDI Bureau of Reclamation (the dam administra-tor), has been conducting a flow evaluation study on the main stem of the Trinity River. Water has been released at varying lev-els above base flow (8.5 m 3 /sec [cms]), each spring in order to facilitate migration of wild and hatchery-raised anadromous fish and to permit evaluation of fish habitat availability and changes as a function of discharge. The timing of these high flow releases has been influenced by many factors, though efforts have been made to mimic historical flow release patterns (Trinity River Res-toration Program 1994). FIG. 1. Riparian habitat composition before (1960) and 26 years after (1989) construction of Trinity and Lewiston Dams on the main stem Trinity River. Estimates were derived from GIS analysis of aerial photo graphs.
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... In unregulated streams, eggs and tadpoles develop through late spring and summer as the stream flow slowly recedes (Kupferberg, 1996;van Hattem et al., 2021). In regulated rivers where dams alter flow regimes, aseasonal flow fluctuations can create high-velocity conditions or rapid stage changes that reduce recruitment by scouring or stranding early life stages (Kupferberg et al., 2012;Lind et al., 1996). Dams also produce flow conditions that can allow non-native predators to flourish (Fuller et al., 2011;Light, 2003). ...
... Time series of egg mass counts were not continuous for some streams, but state-space models that underlie MPVA (see below) allow for the use of incomplete time series by inferring the abundance of egg masses during years without surveys. Egg mass surveys came from a variety of sources, including long-term studies of the ecology of R. boylii (e.g., Kupferberg et al., 2012;Wheeler & Welsh, 2008), monitoring programs for populations affected by dams (e.g., Pacific Gas and Electric Company, 2020;Snover & Adams, 2016), and focused studies on the effects of environmental conditions on breeding (e.g., Gonsolin, 2010;Lind et al., 1996;van Hattem et al., 2021;Wheeler et al., 2015). We treated reaches of the same stream as a single population if they were directly connected without any barrier (e.g., a dam, lake, or reservoir) between the reaches and were surveyed using the same methods by the same research group. ...
... Density dependence was weaker (i.e., higher carrying capacity) in streams with greater seasonality of flow and intermediate rates of change in the spring recession flow. The negative impact of stream regulation on R. boylii populations is supported by field studies documenting lower egg mass density, lower survival rates of egg masses, and reduced growth of larval R. boylii in regulated rivers (Kupferberg et al., 2012;Lind et al., 1996;Wheeler et al., 2015). Aseasonal pulse flows can lead to high mortality for eggs and tadpoles and are one of the primary ways that flow alteration negatively affects populations of R. boylii ...
The decline in amphibian populations is one of the starkest examples of the biodiversity crisis. For stream breeding amphibians, alterations to natural flow regimes by dams, water diversions, and climate change have been implicated in declines and extirpations. Identifying drivers of amphibian declines requires long time series of abundance data because amphibian populations can exhibit high natural variability. Multiple population viability analysis (MPVA) models integrate abundance data and share information from different populations to estimate how environmental factors influence population growth. Flow alteration has been linked to declines and extirpations in the Foothill Yellow‐legged Frog ( Rana boylii ), a stream breeding amphibian native to California and Oregon. To date, no study has jointly analyzed abundance data from populations throughout the range of R. boylii in an MPVA model. We compiled time series of egg mass counts (an index of adult female abundance) from R. boylii populations in 36 focal streams and fit an MPVA model to quantify how streamflow metrics, stream temperature, and surrounding land cover affect population growth. We found population growth was positively related to stream temperature and was higher in the years following a wet year with high total annual streamflow. Density dependence was weakest (i.e., carrying capacity was highest) for streams with high seasonality of streamflow and intermediate rates of change in streamflow during spring. Our results highlight how altered streamflow can further increase the risk of decline for R. boylii populations. Managing stream conditions to better match natural flow and thermal regimes would benefit the conservation of R. boylii populations.
... Additionally, oviposition has been correlated with increasing air temperatures, a proxy for warmer water temperatures that likely facilitate successful reproduction (Wheeler et al. 2018) and presumably correspond with lower summer flows. While tadpoles survive higher flow rates than egg masses (Lind et al. 1996), larval growth and survival may be negatively impacted by flow rates that are exceptionally high or that occur late in the breeding season (Kupferberg et al. 2011). Metamorphosis typically occurs three to four months after hatching, although the timing of metamorphosis is dependent on water temperature and food availability (Ashton et al. 1998). ...
... Late-season releases from the Matthews Dam, however, seem to be buffered at our study site by distance from the dam and incoming tributaries below the dam, as summer peaks were not visible in flow data from the USGS Mad River gauge station near Arcata (USGS NWIS 2017). We found that there were no late season pulses that would impact egg or tadpole survival in any of the three years (Lind et al. 1996;Kupferberg et al. 2012), suggesting Matthews Dam did not negatively impact frog breeding in our study area during these three years. ...
River-breeding foothill yellow-legged frogs (Rana boylii) are endemic to California and Oregon. Across this wide geographic range, many populations have declined due habitat loss, non-native competitors and predators (e.g., American bullfrogs [Lithobates catesbeianus], Centrarchid fish), and disrupted water flow due to dams. Even when flow conditions are not extensively regulated, managers still require basic and region-specific information about the breeding biology of this species to prevent further decline. To document spatiotemporal dynamics of reproductive output during drought and high flow years, we surveyed a 13.5 km reach of the lower Mad River, Humboldt County, CA approximately 70 km downstream of Matthews Dam. We found relatively high densities of egg masses (39 to 59 masses / km). Egg masses were generally laid on small cobbles (mean ±SE diameter = 11 ± 0.24 cm) at depths between 0 and 20 cm, and 95% of egg masses were laid within 6 m of the wetted edge. Egg masses were disproportionately found in the tailouts of fast runs and glides, and found less often than expected in side arms, runs, and riffles than would be expected by chance. Breeding timing appeared to be more related to rapid decreases in stream flow variance than air temperature. Taken with previous information about the species, our results suggest that R. boylii rely on multiple cues to initiate breeding. Our results can be used to help inform breeding timing and habitat use by R. boylii breeding under natural flow regimes in Northern California. Our recommendations for future research include further investigating upland habitat use by post-metamorphic life stages factors that influence breeding site selection.
... This runoff generates predictably timed spring floods in March and April, well ahead of summer monsoon rains. Anurans have early life stages (eggs and tadpoles) that require shallow water depths (Cunningham et al., 2007), and these life stages can be lost if the timing of high-flow events occurs before metamorphosis (Lind Jr. et al., 1996). The role of flooding is important to anurans because populations can be negatively impacted in streams when flows are regulated by dams or diversions (Guzy et al., 2018;Kupferberg et al., 2012). ...
... Because of early recognition of the importance of the FYLF as an indicator species, there has been extensive research around its life history requirements (Kupferberg 1996;Wheeler et al. 2015;Kupferberg et al. 2009;Lind et al. 1996). This research led to the development of the Foothill Yellow-legged Frog Assessment Model, Version 2 (Railsback and Harvey 2015). ...
In this report, we compiled, summarized, analyzed, and modeled water temperature and hydrology data collected from the Trinity River, California to meet six objectives:
1) Construct and populate a comprehensive quality-controlled water temperature dataset for analysis and archive it for future use; 2) Evaluate patterns in the relationship between flow and temperature in space and time before the construction of the TRD, pre-ROD, and post-ROD; 3) Evaluate how ROD flows have affected the thermal regime, temperature compliance, and biological objectives on the Trinity River; 4) Evaluate temperature compliance across multiple years (pre-ROD and post-ROD); 5) Update conceptual models on stream temperature dynamics in the Trinity River; 6) Develop management recommendations to provide water temperatures in the Trinity River that more efficiently meet restoration objectives of the TRRP.
... Here, we report the first observations of the deaths of overwintering tadpoles of two species of Nanorana during check dam maintenance. It is known that check dams have negative impacts on stream channel morphology (Fortugno et al., 2017), water quality, velocity, and substrate fineness (Kang & Kazama, 2012), cause loss of larval microhabitat (Thomas et al., 2019), and influence the breeding ecology of frogs (Lind et al., 1996). However the influence of check dam maintenance has been little documented. ...
We report the deaths of overwintering tadpoles of Nanorana spp. during check dam maintenance events causing localised droughts along the Dhobhighat (Ringali Gad) stream, flowing through the Mussoorie Wildlife Sanctuary, Uttarakhand, India; and discusses the conservation issues and further research required in the scenario.
... Our results are in line with several studies relating to dam construction and significant negative decline in semi-aquatic species (Eskew et al. 2012;Brum et al. 2021;Zwahlen 2022). Due to their high sensitivity to flow regime variations and the possibility of fragmenting habitat, semi-aquatic populations such as H. amphibius face risks of displacement and significant decline (Lind et al. 1996;Liang et al. 2022). It is important to note that some individuals may have moved to suitable locations near the flooded area and survived there (Environmental Resources Management 2007). ...
Landscape changes resulting from human activities have resulted in range restrictions and substantial reductions in population sizes of most animals. The construction of hydroelectric dams has the same effect on species, but the study of their impact on semi-aquatic megafauna species is limited. We examined the response of a Hippopotamus amphibius population to the inundation of their habitat after the construction of a hydroelectric dam in Bui National Park, Ghana. We conducted an abundance and distribution survey of H. amphibius and compared the population size from our results with a pre-dam construction survey to determine changes in the abundance and distribution of the species within the focal area. Furthermore, we conducted a landscape analysis to estimate land cover before and after the dam construction and determined if the changes in land cover were related to the changes in population of H. amphibius. Finally, we conducted selected interviews to understand additional threats to the species perceived by the local population, as indirect effects of the dam construction. Contrary to our original hypothesis on an increase in the abundance of H. amphibius in the medium term (within a decade) through population recovery after the disturbances caused by the construction of the dam, we found lower numbers of H. amphibius after the dam construction, compared to the pre-dam results. The results indicated a reduced abundance from 209 H. amphibius individuals in 2003 to 64 H. amphibius individuals in 2021. Some individuals may have migrated to areas outside the reserve during damming when their habitat was disturbed. The amount of land covered by water increased from 0.41% before damming to 19.01% after damming, which flooded the resting and grazing sites of the H. amphibius. We conclude that the abundance and distribution of H. amphibius significantly and negatively decreased after the construction of the dam at the Bui National Park. We tentatively relate this decrease to the species’ semi aquatic ecology and sensitivity to changes in both the terrestrial and aquatic environment. The activities of human settlement encroachment such as poaching, as well as associated land cover changes, affected the stability of the H. amphibius population. However, as the species can survive in the medium to long term when effective management plans are implemented, we recommend H. amphibius to be given high conservation priorities by enhancing strict laws for habitat protection.
... In the research presented in the next chapter (Chapter 4) I explore the characteristics of waterbodies that Sloane's Froglet occupy in more detail by focussing on the microhabitat that Sloane's Froglet uses within the waterbody. While it may appear at this point that Sloane's Froglet is a generalist, in the next chapter this picture is refined and I propose that while Sloane's Froglets use a variety of waterbodies, calling males in peak breeding season are only using specific parts of them.I chose to focus on the habitat used during the breeding period, as management of breeding habitat is a core requirement for the ongoing survival of a threatened species (e.g.Ferreira & Beja, 2013;Lind, Welsh Jr, & Wilson, 1996;Thomas, Owen-Smith, Drake, & Alexander, 2014). Habitat variables for the waterbodies surveyed in this study were collected in one season only, in the peak calling period, winter and early spring, which is the wettest time of the year in the study region. ...
Sloane’s Froglet, Crinia sloanei, is a threatened and little-known frog with a historical distribution in the Australian states of New South Wales (NSW) and Victoria (Vic). I investigated Sloane’s Froglet distribution and habitat (chapters 2, 3 and 4). As my intention was for the ecological knowledge generated to be applied, I undertook a transdisciplinary case study approach, and used social research methods to explore knowledge exchange between researchers and practitioners, and advocacy (chapters 5 and 6). I discuss the research approach in Chapter 7.
I undertook distribution studies from 2010 to 2013 and established the presence of an important extant population of Sloane’s Froglet in southern NSW and northern Vic, within a highly modified landscape that is quickly becoming more densely settled by humans. I investigated the habitat characteristics of waterbodies occupied by Sloane’s Froglet in winter, its peak breeding period, by comparing the physical and vegetation characteristics of 54 occupied and 40 unoccupied waterbodies. I determined a core calling period for Sloane’s Froglet and detection probabilities for the surveys undertaken. Sloane’s Froglet occupied both constructed and “natural” waterbodies with a variety of features, including differing hydroperiods and surrounding landuse. The waterbodies that Sloane’s Froglet occupied differed from unoccupied waterbodies by containing a greater percent cover of small stem-diameter emergent vegetation; often connecting with adjacent ephemeral shallow overflows; having gently sloping banks; and less bare ground on the banks within two metres of the waterbody. I explored the microhabitat and relative spatial positioning of Sloane’s Froglet within waterbodies by comparing the characteristics of 54 sites around individual male Sloane’s Froglet with 57 randomly selected unoccupied sites. Sloane’s Froglets were found to always call from within the waterbody rather than on the bank, distinguishing them from other sympatric Crinia species. Sloane’s Froglets occurred at sites with less of the site above the water level, and at significantly shallower water depths, than unoccupied sites. Sloane’s Froglets were closer to other Sloane’s Froglets and other calling male frogs at occupied sites, suggesting clustering behaviours. Recommendations for applying this knowledge to benefit Sloane’s Froglet are included in chapters 2 to 4.
I used an autoethnographical approach to describe the advocacy I undertook during the research process and to reflect on knowledge exchange between me as a researcher-advocate, environmental practitioners and the broader community. I further investigated the constraints and enablers of knowledge sharing and utilisation by exploring the insights of 11 environmental practitioners whose work can benefit water-dependent biodiversity. Exploration of the semi-structured interviews suggests that exchange and utilisation of new knowledge is impacted by: how knowledge and knowledge sharing processes are perceived; the media for knowledge communication; continual learning and adaptive management; personal values and the role of advocacy; and, external filters such as political will and institutional processes. The transdisciplinary case study results suggest that my applied research will not be utilised without an advocative approach, preferably with the support of an influential person and validation of an established organisation. In addition, a collaborative research approach or the coproduction of knowledge with practitioners will enable the management application of the ecological research.
In Chapter 7 I present a framework that I call “intentional ecology” based in conservation biology, systems and contemporary feminist theories to support the transdisciplinary and applied research approach. Intentional ecology provides a platform for the use of multiple methodologies and an imperative for action in which knowledge exchange and advocacy are understood as implicit to ecological research with management implications.
Microhyla eos is a recently described species in the family Microhylidae from the Eastern Himalayan biodiversity
hotspot in Arunachal Pradesh, India, for which very little natural history information is known. We here provide a detailed
description of the breeding ecology of the species with information on its amplexus, oviposition site selection, and advertisement
call. The call has an average duration of 692 ms with an average pulse rate of 43 pulses per second. The dominant frequency ranged
from 1.5–2.8 kHz with an average maximum amplitude of 4060.17 kU. We also present comparisons with other microhylids from
South and Southeast Asia.
We present observations on the breeding biology of Polypedates braueri from Mizoram, India. Breeding activity was triggered by the onset of the southwest monsoon and lasted from April–September, reaching peak activity by early July when the ambient air temperature ranged from 15.4–33.4°C, relative humidity was 39.5–98.7%, and 57–647 mm of rain fell. We observed terrestrial oviposition in foam nests of diameter 7–10 cm. The mean female snout-to-vent length (SVL) was 54.5 ± 4.5 mm (n = 11) and mean clutch size was 306 ± 17 (n = 10); a significant positive correlation was observed between female body size and clutch size (r = 0.55). The frequency of male calls ranged from 843.75–1406.25 Hz. A single call is made up of 1–5 notes with varying durations (43–598 ms), depending on the number of notes in the call. Male vocalization is distinct compared to congener.
A symposium was held 8 August 1991, at the annual meeting of the Society for the Study of Amphibians and Reptiles and The Herpetologists' League in University Park, Pennsylvania. The topic, "Amphibian Declines and Habitat Acidification" was selected for its relevance to the topical issues of a precipitous drop in many amphibian populations, and possible causation by acidic atmospheric deposition. As organizers, we felt that a rigorous approach to these issues requires meticulous field documentation of population fluctuations and correlated environmental measures of pollution, along with an experimental ecotoxicological analysis of possible anthropogenic causation. Because of the potential for large-scale environmental change acting synergistically with pollution across landscapes, the experimental elucidation of cause and effect will be extremely difficult. It appears that some amphibian populations fluctuate in an episodic fashion, but there are no long-term data bases adequate to determine whether particular declines are uniequivocally due to acidic deposition from non-point sources, other anthropogenic causes, natural causes, or interactions among them. This series of papers deals with the effects of acidic waters and soils on amphibians in England and North America. It is very clear that acidic habitats of natural and polluted origin exclude certain species and cause sub-lethal and lethal effects. However, no data are at hand which show directly that anthropogenic acidification causes amphibian populations to decline. There is considerable interest in the development of bioindicators of habitat decline. Net loss of body sodium and the embryonic curling defect in amphibians are examples of the best of such direct bioassays in acidified aquatic and terrestrial habitats. There is a strong need for standardization of test conditions so that better comparisons can be made among results from laboratories in different geographic regions. We recommend that a number of sites be chosen for long-term (10 year minimum) study of the relation between amphibian population cycles and anthropogenic change. This research would provide data not only specifically pertinent to the issue of amphibian declines, but would also provide valuable tests of the usefulness of amphibians as general bioindicators of ecosystem decline in response to anthropogenic stress. These issues are complex and are not amenable to quick solutions. A sustained commitment is needed by researchers and funding agencies to provide long-term monitoring and rigorous experimental tests of the causes of any declines in especially sensitive biotic components of ecosystems.
