Evaluating Watershed Condition: Bottom Up Vs. Top Down Approaches?

Habitat degradation has been identified as one of the major factors affecting the declines of fishes in the Columbia River Basin. The condition of physical habitat and the biotic integrity of stream systems are often directly correlated with substantial alterations to key landscape attributes. As such, numerous approaches to measure watershed condition have been developed. Here, we compare two separate measures of watershed condition: 1) a GIS-based measure of condition, i.e., top down; and 2) a ground based assessment of condition, i.e., bottom up), using field data collected across 1200 sites in the Interior Columbia River Basin under the PIBO Effectiveness Monitoring Project. With our GIS approach, we integrate land management and natural disturbance from watershed upstream of sample reaches into an overall watershed condition score. With our bottom-up approach, we integrate stream temperature data, indices of macroinvertebrate health, and an index of physical habitat condition from reach-level field data into an overall condition score. Our results indicate significant differences in assessments of condition across the two methods, as the GIS approach ranked considerably more watersheds with management activities into a low condition category than found in the bottom-up approach. Conversely, the GIS approach also categorized most watersheds with no or minimal management activities, i.e., reference, as low risk, while the field-based, bottom up approach illustrated a wide range of condition of reference sites due to natural disturbances. Our results suggest GIS-based approaches tended to quantify the ‘risk’ rather than condition within watersheds. The bottom-up approach tended to quantify actual conditions within streams, without consideration of potential risks associated with land management activities. Here, we advocate the most beneficial approach that would be some combination of the two to help guide and prioritize restoration activities to enhance habitat conditions and minimize risk of catastrophic disturbances

Quantifying Temporal Variability in Stream Habitat Data: Implications for Restoration and Monitoring

Quantifying natural and anthropogenic-induced levels of temporal variability is essential for robust trend analyses and for evaluating the effectiveness of restoration activities or changed management actions. Here, we used data collected as part of the Pacfish/Infish Biological Effectiveness Monitoring Project to evaluate the extent of temporal variability in instream habitat collected at the reach scale. We integrated habitat data collected yearly (2001-2009) at 50 sites experiencing a range of management activities into our analyses to better understand the consistency of temporal variability in watersheds with inherently different landscape characteristics and disturbance regimes. We initially decomposed variance estimates to remove site-to-site variability, sampling error, and year effects and use the remaining variance as a measure of site-specific temporal variability. We then relate this temporal variability to landscape, management, and climate attributes at multiple scales to better understand which characteristics result in more or less variability in habitat attributes at specific sites. Our results suggest temporal variability differs significantly across individual sites and attributes within sites, indicating our ability to detect significant changes as a result of management changes and/or restoration efforts are context dependent. The spatial scale of landscape attributes, e.g., stream buffer vs. catchment, related to temporal variability also varied across individual attributes. Our efforts highlight the importance of considering site specific measures of temporal variability as they relate to specific restoration and management goals

Thermal controls of Yellowstone cutthroat trout and invasive fishes under climate change

We combine large observed data sets and dynamically downscaled climate data to explore historic and future (2050-2069) stream temperature changes over the topographically diverse Greater Yellowstone Ecosystem (elevation range=824-4017m). We link future stream temperatures with fish growth models to investigate how changing thermal regimes could influence the future distribution and persistence of native Yellowstone cutthroat trout (YCT) and competing invasive species. We find that stream temperatures during the recent decade (2000-2009) surpass the anomalously warm period of the 1930s. Climate simulations indicate air temperatures will warm by 1 °C to >3 °C over the Greater Yellowstone by mid-21st century, resulting in concomitant increases in 2050-2069 peak stream temperatures and protracted periods of warming from May to September (MJJAS). Projected changes in thermal regimes during the MJJAS growing season modify the trajectories of daily growth rates at all elevations with pronounced growth during early and late summer. For high-elevation populations, we find considerable increases in fish body mass attributable both to warming of cold-water temperatures and to extended growing seasons. During peak July to August warming, mid-21st century temperatures will cause periods of increased thermal stress, rendering some low-elevation streams less suitable for YCT. The majority (80%) of sites currently inhabited by YCT, however, display minimal loss (<10%) or positive changes in total body mass by midcentury; we attribute this response to the fact that many low-elevation populations of YCT have already been extirpated by historical changes in land use and invasions of non-native species. Our results further suggest that benefits to YCT populations due to warmer stream temperatures at currently cold sites could be offset by the interspecific effects of corresponding growth of sympatric, non-native species, underscoring the importance of developing climate adaptation strategies that reduce limiting factors such as non-native species and habitat degradation.Keywords: trout, climate change, growth, non-natives, Greater Yellowston

Population Density Estimates and Growth Rates of Eleutherodactylus coqui in Hawaii

The Puerto Rican terrestrial frog (Eleutherodactylus coqui) has received considerable attention in Hawaii because of its rapid spread, loud mating calls, and its potential threat to native species. Thus far, its invasion potential on the Island of Hawaii remains poorly understood. Critical components for determining this potential are robust estimates of abundance and vital rates across habitat types. To address this lack of information, we used mark-recapture methods to estimate E. coqui survival and abundance, determine growth rates of adult male and female frogs, and relate densities to elevation, snout–vent length (SVL), habitat structure, and invertebrate abundance. Mean adult E. coqui density across eight sites was 62 ± 12 adults/100 m2 and ranged from 6-138 adults/100 m2. Our three-year mean adult density estimates were three times greater at three of our study sites (100 adults/100 m2) than the highest long-term estimates from Puerto Rico (33 adults/100 m2). Mean individual growth rates were 0.0078 mm/day (± 0.007 SD, N = 87) for males and 0.0097 mm/day (± 0.009 SD, N = 11) for females. Frogs of similar size were found to be growing slower in Hawaii than Puerto Rico. We found no relationship between elevation and E. coqui density or elevation and SVL or between invertebrate abundance and E. coqui density. However, there was a positive relationship between understory structure and E. coqui density. This relationship suggests that removing understory structure could reduce E. coqui densities, although other potential implications of this management treatment should be considered

Quantitative Assessment of the Limiting Factors Affecting Salmonid Populations

Native salmonids have declined throughout their range in response to habitat loss and fragmentation in combination with other factors. Quantification of the links between habitat needs and demographic parameters are necessary to prevent further loss of these species and guide restoration efforts. However, in order to direct recovery efforts, we need research techniques that can account for multiple life-history strategies, accurately assess populations across landscapes, and understand the specific age/stage class that is potentially limiting population growth rates. To address these concerns, we are conducting a multiple system, mark/recapture project in conjunction with habitat surveys to understand the limiting factors affecting bull trout populations in northeastern Oregon. Our sampling design in combination with current technology allow for effective sampling across different life-history strategies and across spatial differences within each watershed, and ultimately will allow for direct comparisons of potential bottlenecks between populations. Our results suggest that the current monitoring techniques may not be appropriate for effectively monitoring the population trends of different bull trout life-history forms. Furthermore, these results indicate that monitoring techniques of declining salmonid populations need to be validated with respect to current management objectives

A Hierarchical Examination of Bull Trout Habitat Relationships in Northeast Oregon

Bull trout have declined throughout their range in response to habitat loss and fragmentation in combination with other factors. Quantification of the links between habitat needs and bull trout abundance is necessary for preventing further losses of this species and ultimately to guide restoration efforts. We are conducting a multi-system, multi-scale effort to examine the habitat use and preference of bull trout in northeast Oregon. We measured bull trout habitat use and availability independently with snorkeling and traditional habitat measurement techniques at micro and reach scales in the South Fork Walla Walla River (SFWWR). At the reach scale, bull trout density was best explained by large woody debris and the presence of O. mykiss spp., while sinuosity and percent pools appeared to be unimportant. At the microhabitat scale, bull trout strongly selected deeper water, slower bottom velocities, and cover including boulders and LWD. In contrast to other studies, bull trout in the SFWW showed no preference in substrate size, suggesting that substrate is not limiting factor and may have little influence in the SFWWR. These results highlight the need for a predictive model, which can be spatially validated across the Columbia River Basin and subsequently used to guide recovery efforts

Detecting changes in abundance of endangered species: understanding the accuracy, precision, and costs

Using empirical field data for bull trout (Salvelinus confluentus), we evaluated the trade-off between power and sampling effort–cost using Monte Carlo simulations of commonly collected mark–recapture–resight and count data, and we estimated the power to detect changes in abundance across different time intervals. We also evaluated the effects of monitoring different components of a population and stratification methods on the precision of each method. Our results illustrate substantial variability in the relative precision, cost, and information gained from each approach. While grouping estimates by age or stage class substantially increased the precision of estimates, spatial stratification of sampling units resulted in limited increases in precision. Although mark–resight methods allowed for estimates of abundance versus indices of abundance, our results suggest snorkel surveys may be a more affordable monitoring approach across large spatial scales. Detecting a 25% decline in abundance after 5 years was not possible, regardless of technique (power = 0.80), without high sampling effort (48% of study site). Detecting a 25% decline was possible after 15 years, but still required high sampling efforts. Our results suggest detecting moderate changes in abundance of freshwater salmonids requires considerable resource and temporal commitments and highlight the difficulties of using abundance measures for monitoring bull trout populations

Annual Variation of Spawning Cutthroat Trout in a Small Western USA Stream: A Case Study with Implications for the Conservation of Potamodromous Trout Life History Diversity

Little is known about the variability in the spatial and temporal distribution of spawning potamodromous trout despite decades of research directed at salmonid spawning ecology and the increased awareness that conserving life history diversity should be a focus of management. We monitored a population of fluvial–resident Bonneville Cutthroat Trout Oncorhynchus clarkii utah in a tributary to the Logan River, Utah, from 2006 to 2012 to gain insight into the distribution and timing of spawning and what factors may influence these spawning activities. We monitored Bonneville Cutthroat Trout using redd surveys with multiple observers and georeferenced redd locations. We documented an extended spawning period that lasted from late April to mid-July.