James E. Whitney

Climate Change Effects on North American Inland Fish Populations and Assemblages

Climate is a critical driver of many fish populations, assemblages, and aquatic communities. However, direct observational studies of climate change impacts on North American inland fishes are rare. In this synthesis, we (1) summarize climate trends that may influence North American inland fish populations and assemblages, (2) compile 31 peer-reviewed studies of documented climate change effects on North American inland fish populations and assemblages, and (3) highlight four case studies representing a variety of observed responses ranging from warmwater systems in the southwestern and southeastern United States to coldwater systems along the Pacific Coast and Canadian Shield. We conclude by identifying key data gaps and research needs to inform adaptive, ecosystem-based approaches to managing North American inland fishes and fisheries in a changing climate.

Physiological Basis of Climate Change Impacts on North American Inland Fishes

Global climate change is altering freshwater ecosystems and affecting fish populations and communities. Underpinning changes in fish distribution and assemblage-level responses to climate change are individual-level physiological constraints. In this review, we synthesize the mechanistic effects of climate change on neuroendocrine, cardiorespiratory, immune, osmoregulatory, and reproductive systems of freshwater and diadromous fishes. Observed climate change effects on physiological systems are varied and numerous, including exceedance of critical thermal tolerances, decreased cardiorespiratory performance, compromised immune function, and altered patterns of individual reproductive investment. However, effects vary widely among and within species because of species, population, and even sex-specific differences in sensitivity and resilience and because of habitat-specific variation in the magnitude of climate-related environmental change. Research on the interactive effects of climate change with other e...

Adapting Inland Fisheries Management to a Changing Climate

Natural resource decision makers are challenged to adapt management to a changing climate while balancing short-term management goals with long-term changes in aquatic systems. Adaptation will require developing resilient ecosystems and resilient management systems. Decision makers already have tools to develop or ensure resilient aquatic systems and fisheries such as managing harvest and riparian zones. Because fisheries management often interacts with multiple stakeholders, adaptation strategies involving fisheries managers and other partners focused on land use, policy, and human systems, coupled with long-term monitoring, are necessary for resilient systems. We show how agencies and organizations are adapting to a changing climate in Minnesota and Ontario lakes and Montana streams. We also present how the Florida Fish and Wildlife Commission created a management structure to develop adaptation strategies. These examples demonstrate how organizations and agencies can cope with climate change effects on...

Identifying Alternate Pathways for Climate Change to Impact Inland Recreational Fishers

Fisheries and human dimensions literature suggests that climate change influences inland recreational fishers in North America through three major pathways. The most widely recognized pathway suggests that climate change impacts habitat and fish populations (e.g., water temperature impacting fish survival) and cascades to impact fishers. Climate change also impacts recreational fishers by influencing environmental conditions that directly affect fishers (e.g., increased temperatures in northern climates resulting in extended open water fishing seasons and increased fishing effort). The final pathway occurs from climate change mitigation and adaptation efforts (e.g., refined energy policies result in higher fuel costs, making distant trips more expensive). To address limitations of past research (e.g., assessing climate change impacts for only one pathway at a time and not accounting for climate variability, extreme weather events, or heterogeneity among fishers), we encourage researchers to refocus their ...

Consecutive wildfires affect stream biota in cold- and warmwater dryland river networks

Climate change and fire suppression have altered fire regimes globally, leading to larger, more frequent, and more severe wildfires. Responses of coldwater stream biota to single wildfires are well studied, but measured responses to consecutive wildfires in warmwater systems that often include mixed assemblages of native and nonnative taxa are lacking. We quantified changes in physical habitat, resource availability, and biomass of cold- and warmwater oligochaetes, insects, crayfish, fishes, and tadpoles following consecutive megafires (covering >100 km2) in the upper Gila River, New Mexico, USA. We were particularly interested in comparing responses of native and nonnative fishes that might have evolved under different disturbance regimes. Changes in habitat and resource availability were related to cumulative fire effects, fire size, and postfire precipitation. The 2nd of 2 consecutive wildfires in the basin was larger and, coupled with moderate postfire discharge, resulted in increased siltation and decreased algal biomass. Several insect taxa responded to these fires with reduced biomass, whereas oligochaete biomass was unaffected. Biomass of 6 of 7 native fish species decreased after the fires, and decreases were associated with site proximity to fire. Nonnative fish decreases after fire were most pronounced for coldwater salmonids, and warmwater nonnative fishes exhibited limited responses. All crayfish and tadpoles collected were nonnative and were unresponsive to fire disturbance. More pronounced responses of native insects and fishes to fires indicate that increasing fire size and frequency threatens the persistence of native fauna and suggests that management activities promoting ecosystem resilience might help ameliorate wildfire effects.

Habitat associations of stream fishes in protected tallgrass prairie streams

Abstract Describing fish habitat associations and their relevance to conservation remains a central challenge in stream fish ecology. Unfortunately, there are limited opportunities to investigate these associations in unaltered systems and identify critical habitats used by native fishes. Investigation of fish habitat associations in tallgrass prairie is especially vital, owing to their widespread destruction. Our study aim was to identify habitat factors associated with the distribution and density of fishes in two protected tallgrass prairie stream watersheds in eastern Kansas: Kings Creek on the Konza Prairie Biological Station (KPBS) and Fox Creek on the Tallgrass Prairie National Preserve (TPNP). We sampled fishes and measured eight habitat variables at three sites on KPBS (2006–2011) and four sites on TPNP (2008–2011). Multiple regression suggested that species richness was positively associated with pool area (partial r  =  0.70) and discharge (partial r  =  0.50) in Fox Creek (df  =  15, Adj. R2  =  0.60, P < 0.001). In Kings Creek, species richness was only associated with pool area (df  =  17, R2  =  0.44, P < 0.001). Redundancy analyses showed common prairie fish species exhibit ontogenetic habitat associations, partitioning adults in deep and juveniles in shallow pools. Strong species area relationships in these minimally altered systems indicates large volume habitats have greater species richness, suggesting water diversions or extractions that reduce habitat are likely to cause declines in native biodiversity.

Introduced Flathead Catfish Consumptive Demand on Native Fishes of the Upper Gila River, New Mexico

AbstractPredation by nonnative fish is often cited as a leading cause of declining native fish populations, but quantifying these negative interactions is difficult. Bioenergetics modeling provides a tool to estimate consumptive demand of nonnative species and to identify those that pose the greatest threats to native biota. We used bioenergetics modeling to estimate the consumptive demand of Flathead Catfish Pylodictis olivaris on native fishes in the upper Gila River, New Mexico, across an elevational gradient. Model results were coupled with measured densities and size structure of Flathead Catfish populations, as well as water temperatures, to predict its predatory threat. Potential consumption was highest at lower elevation sites because of higher water temperatures, but actual consumption was highest at mid-elevation sites because of the prevalence of larger individuals there. Potential annual consumptive demand of Flathead Catfish on native fish across our nine sampling sites ranged from 0.0 to 3.1...

Alternative spawning strategy and temperature for larval emergence of longfin dace (Agosia chrysogaster) in stream mesocosms

Abstract To determine if the strategy of spawning in saucer-like depressions is obligate or facultative for longfin dace (Agosia chrysogaster), we collected adults from four sites in the upper Gila River (southwestern New Mexico), stocked them in separate outdoor stream-mesocosms lined with cobble substrate, and made daily observations for the presence of saucer-nests and hatched larvae. Larvae were observed from three of the four mesocosms and emerged at temperatures ranging from 19.2–24.0°C. The absence of saucer-nests in all mesocosms throughout the study indicates that longfin dace can spawn over cobble substrate and have larvae hatch successfully, suggesting that longfin dace can use an alternate spawning strategy when sand substrate is not available for construction of saucer-nests.

Dietary overlap of invertivorous fishes and macroinvertebrates in the Gila River, New Mexico

Abstract The diets of stoneflies (Perlodidae) and hellgrammites (Corydalidae) from the Gila River, New Mexico, were quantified and compared to diets of three native fishes that also occupy riffle habitats along with stoneflies and hellgrammites: speckled dace (Rhinichthys osculus); longfin dace (Agosia chrysogaster); desert sucker (Catostomus clarkii). The highest overlap occurred among corydalids, desert sucker, and longfin dace, which had diets dominated by amorphous detritus. Speckled dace and perlodids consumed less amorphous detritus, with nymphs of mayflies and larval black flies dominating their respective diets. Our results suggest moderate to high overlap of resources among invertivorous fishes and invertebrates. Although we found high dietary overlap between corydalids and two fishes, it is unclear whether amorphous detritus is a limiting resource that drives competitive interactions.