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Tourism and recreation in protected areas may compromise conservation values if their forms and volumes exceed the area’s tolerance. Disturbance-sensitive species such as wild and semi-domestic reindeer (Rangifer tarandus tarandus) in most mountain areas in Fennoscandia are particularly vulnerable to humans, but disturbance research seldom includes data on the human component of this co-existence. By estimating the visitor volume in space and time and visitor characteristics in the largest national park and wild reindeer range in Norway we analyzed reindeer trail crossing propensity and examined the spatial overlap between humans and GPS-collared female reindeer (n¼98) during summer. The data showed that female reindeer herds used areas with overall less human traffic and recreational infrastructure. Reindeer herds started avoiding crossing hiking trails used by more than 10–15 persons per day and avoided crossing trails when visitor volumes exceeded 30–50 persons per day. During the hunting season, the herds were largely dispersed and crossed over trails independent of visitor volume, indicating a collective flight response to hunters. We discuss how including data on human use can further our understanding of ecological effects in disturbance research and how it can improve management interventions for better co-existence between humans and reindeer.

Disturbance of wild reindeer from human activity is a key challenge for wildlife management. We reviewed recent literature on reindeer disturbance in Northern Europe and discuss a major lacuna in this field of research, namely knowledge about the complexity of human behaviour, which is the major agent of disturbance. Past studies have rarely included detailed data on human activities, but instead treated fixed infrastructure as valid proxies for human presence. However, ignoring the dynamic and flexible nature of human agency as a driver of disturbance may bias our interpretation of the observed responses. We argue that incorporating information about the spatiotemporal patterns of human use of infrastructure and the characteristics of the users may greatly improve our knowledge of the potential impacts on wild and semi-domestic reindeer populations and contribute to improved management of their ranges. Human disturbance; population effects; reindeer behaviour; protected areas; management

Interactions among predators can have important consequences for lower trophic levels. Here, we use individual tag data on juvenile salmonids to quantify how their geographic, taxonomic, and life-history representation in the diets of great blue herons (Ardea herodias) changed after a pair of bald eagles (Haliaeetus leucocephalus) usurped the colony's nesting site, forcing the colony to relocate. Heron diet composition changed significantly despite the short relocation distance (4.1 km). This was driven by a shift in space use, as herons to a greater extent began consuming fish from a river basin farther away from the bald eagle nest. As a consequence the species composition in heron diets changed significantly, with the largest increase in coho (Oncorhynchus kisutch) and largest decrease in Chinook salmon (O. tshawytscha). The representation of Chinook life-history types in the diets also shifted. Fall Chinook was the numerically dominant life-history type in the diets but decreased relative to ...

A paradox in managing threatened and endangered species is the increased need for documenting population status, which in many instances requires capturing and handling individuals. Electrofishing is a widely used method for sampling fish in small streams, but the potential for detrimental effects call for its careful use. Methods that reduce exposure for individual fish, yet still provide useful abundance estimates, are therefore desirable. Using data from a juvenile steelhead (Oncorhynchus mykiss) monitoring program in Idaho, we quantified variation and bias in capture probability from three-pass depletion electrofishing, and evaluated a method for indexing abundance based on single-pass electrofishing. Capture probability varied primarily at the level of sampling visits, with little spatial variation (i.e. at the level of the study sites). Water temperature, channel depth and, to a lesser degree, discharge best described the variation in capture probability between sampling events. We found no effect of previous capture and handling on individual capture probability, and the capture probability did not differ between subyearling and overyearling fish. Finally, a simple mixed-effects model with study site as a random effect, which related first-pass catch to the associated multiple-pass removal estimate, explained 91% of the variation in our data. The main limitation of the approach is that it does not provide error propagation and confidence intervals to the abundance estimates. However, the approach can be useful where multiple depletion electrofishing data exist, and when a single point estimate is sufficient to monitor major population trends in small streams.

In territorial stream salmonids, asymmetric competition can perpetuate individual size differences over time, but the extent to which this is manifested can be environmentally mediated. Here we study the variation in juvenile steelhead (Oncorhynchus mykiss) growth rates to identify the conditions (population density and water temperature) under which an individual’s size relative to its conspecifics conferred an advantage. Among steelhead rearing in the same stream section we found that relatively larger individuals on average grew faster than smaller conspecifics. However, comparing across stream sections there was a negative interaction between relative size and water temperature. The effect of an individual’s relative size on its growth rate decreased as temperatures were increasing, indicating that the advantages of being large diminished during periods of high temperatures or in locations with relatively higher temperatures. Compared to temperature, the effects of population density on the growth rate were less substantial. The results suggest that larger individuals on average acquire more resources than smaller individuals, and demonstrate that water temperature exerts an important, modulating control over growth performance in heterogeneous environments.

Recent declines of anadromous salmonids in the Pacific Northwest have prompted a need to understand the factors limiting populations across habitats and life stages. In the weeks following emergence from the spawning gravel, juvenile salmonids have limited swimming capacity and can be particularly vulnerable to predation by piscivores, such as sculpins (Cottus sp.) which are widespread in Pacific Northwest streams. The objective of this study was to investigate the extent to which sculpin prey on newly emerged steelhead (Oncorhynchus mykiss) in a threatened population in Idaho. Three species of sculpin were present in the watershed, including Paiute (C. beldingii), mottled (C. bairdii), and torrent (C. rhotheus) sculpin. Gut content analyses of 360 sculpin showed that invertebrates were the dominant food source (> 85% of all sculpin preyed mainly on invertebrates), and piscivory was rare (< 2%). None of the samples contained steelhead alevins. We conclude that there was no indication of predation...

Forested lands serve multiple needs, and the priorities that go into balancing the competing demands can vary over time. In addition to being the source of timber and other natural resources, forested lands provide a number of other services such as biodiversity conservation and opportunities for outdoor recreation. While allocations that enhance conservation and recreation can involve expenses and lost revenue, mechanisms exist to provide landowners with incentives to make such contributions. Here, we review the literature and present a conceptual framework that can help landowners envision possible contributions towards bolstering outdoor recreation opportunities on their lands. The framework classifies forests within a simple conceptual space defined by two axes: (1) the spectrum of intensity of recreational use, and (2) the level of economic contribution required by landowners to meet recreational demands of visitors to their lands. The resulting matrix consists of four broad categories that can be used in forest management zoning as seen from an outdoor recreation perspective: general and special considerations for recreational opportunities and biodiversity, wilderness and nature reserves, and service areas. These categories have different tolerances for active silviculture and require shifting harvest practices spatially within the forest property. While timber revenues may decrease with shifting allocations, other sources of revenue may open up. With an increasingly urban population and rising demands for natural resources, it is prudent for landowners and land use planners to consider zoning their properties to better handle potential conflicts. The framework presented here provides a simple, structured approach to visualize future challenges and opportunities.

Self-thinning patterns are frequently used to describe density dependence in populations on timescales shorter than the organism's life span and have been used to infer carrying capacity of the environment. Among mobile animals, this concept has been used to document density dependence in stream salmonids, which compete over access to food and space. The carrying capacity, growth conditions, and initial cohort sizes often vary between streams and stream sections, which would influence the onset and strength of the density dependence. Despite much effort in describing habitat relationships in stream fishes, few studies have explicitly tested how the physical environment affects the slope of the thinning curves. Here, we investigate the prevalence and strength of self-thinning in juvenile stages of a steelhead (Oncorhynchus mykiss) population in Idaho, USA. Further, we investigate the roles of local physical habitat and metabolic constraints in explaining the variation in thinning curves among study sites in the watershed. Only yearling steelhead exhibited an overall significant thinning trend, but the slope of the mass–density relationship (−0.53) was shallower than predicted by theory and reported from empirical studies. There was no detectable relationship in subyearling steelhead. Certain abiotic factors explained a relatively large portion of the variation in the strength of the self-thinning among the study reaches. For subyearling steelhead, the slopes were negatively associated with the average water depth and flow velocity in the study sites, whereas slopes in yearlings were steeper in sites that incurred a higher metabolic cost. Our results show that the prevalence and strength of density dependence in natural fish populations can vary across heterogeneous watersheds and can be more pronounced during certain stages of a species' life history, and that environmental factors can mediate the extent to which density dependence is manifested in predictable ways.

Physical habitat characteristics can affect the abundance and distribution of organisms, and are frequently used to predict the standing crop of stream fish for purposes of understanding their ecology and better direct management. However, the spatial scale of the investigation and the resolution of the data can affect the outcome of such analyses. In this study we coupled watershed-level characteristics with instream habitat variables to model the density of two age-classes of juvenile steelhead Oncorhynchus mykiss in a watershed in the Clearwater River basin, Idaho. Density varied considerably across time and space. Variance partitioning showed that 41–50% of the variances in density were due to unexplained differences between sampling occasions (residual variance), and the rest resulted from variation at the site and site-and-year levels, depending on the age-class. Instream habitat variables better explained the variation in density than did models that included watershed-level characteristics...

Across taxa, it is generally accepted that there are fitness advantages to rapid growth early in life. For stream-dwelling salmonids, however, high temperatures and associated energetic costs during the summer growing season might offset or even prevent the competitive advantage of large body size. Our overall objective was to understand the relative importance of factors that can cause variation in growth rates in an age-0 cohort of wild steelhead (Oncorhynchus mykiss) in Idaho, USA, where temperatures approach, and temporarily exceed, their tolerance level. For individually tagged fish inhabiting the same stream reach, we found that growth rates were negatively related to fish mass (slopes of the two best approximating models were both −0.024). Comparing growth rates from 16 different stream reaches throughout the watershed, we found that temperature-induced metabolic cost was the single best approximating model (AIC wi = 1.0) of the variation in individual growth rates. The bioenergetic model showed that mass-specific metabolic costs decreased with mass, but the absolute energetic demands increased over the same size range. Because temperature had a multiplicative effect on metabolic cost, our results suggest that the effect of food limitation increased with fish size. We conclude that high water temperatures pose energetic bottlenecks and can be a potentially strong mechanism limiting growth in juvenile salmonids in summer, particularly as streams in the region experience warming trends.

In organisms with flexible and indeterminate growth, demographic density dependence can affect both individual fitness and population dynamics. Recent work in stream salmonids suggests that individual growth rates can be depressed even at low population densities, which warrants examination of populations previously assumed to be below carrying capacity. We investigated the effects of population density on individual growth rates in a threatened population of steelhead (Oncorhynchus mykiss) in a tributary to the Clearwater River in Idaho, USA. We followed a mark-recapture design where we visited 16 study sites on average five times per year from 2010 to 2012. The 95% confidence interval for average growth rates (% change in body mass per day) for subyearlings were [0.82, 1.0]) and [0.16, 0.30] for yearling steelhead. Variance decomposition showed that the variation in growth rates could be attributed equally to individual- and visit-level factors in subyearlings, whereas almost two-thirds of the variance in yearling growth rates could be attributed to individual-level factors. Growth rates in the subyearling age class were negatively related to the densities of yearling steelhead, but not vice versa. Yearling growth rates showed no evidence of density dependence. Finally, density in interaction with water temperature did not affect growth rates of either age class. Our results demonstrate that density dependence can pose constraints on individual growth rates at low population densities (