Intestinal microbial profiles of wild Alaskan rainbow trout () characterized by 16S rRNA amplicon data.

Rainbow trout () is a dominant aquaculture species of the Salmonidae family, native only to the North Pacific. Recently, the gut microbiome has been shown to reflect the health status and responses to environmental changes in farmed fish. In this analysis we investigated the microbiome composition of the intestinal tract in 20 wild-caught rainbow trout specimens sampled in Alaska, USA.

Watershed features shape spatial patterns of fish tissue mercury in a boreal river network.

Freshwater mercury (Hg) contamination is a widespread environmental concern but how proximate sources and downstream transport shape Hg spatial patterns in riverine food webs is poorly understood. We measured total Hg (THg) in slimy sculpin (Cottus cognatus) across the Kuskokwim River, a large boreal river in western Alaska and home to subsistence fishing communities which rely on fish for primary nutrition. We used spatial stream network models (SSNMs) to quantify watershed and instream conditions influencing sculpin THg.

Declines in body size of sockeye salmon associated with increased competition in the ocean.

Declining body sizes have been documented for several species of Pacific salmon; however, whether size declines are caused mainly by ocean warming or other ecological factors, and whether they result primarily from trends in age at maturation or changing growth rates remain poorly understood. We quantified changes in mean body size and contributions from shifting size-at-age and age structure of mature sockeye salmon returning to Bristol Bay, Alaska, over the past 60 years. Mean length declined by 3%, corresponding to a 10% decline in mean body mass, since the early 1960s, though much of this decline occurred since the early 2000s.

Getting ahead of climate change for ecological adaptation and resilience.

Changing the course of Earth's climate is increasingly urgent, but there is also a concurrent need for proactive stewardship of the adaptive capacity of the rapidly changing biosphere. Adaptation ultimately underpins the resilience of Earth's complex systems; species, communities, and ecosystems shift and evolve over time. Yet oncoming changes will seriously challenge current natural resource management and conservation efforts.

Assessing the potential for demographic restoration and assisted evolution to build climate resilience in coral reefs.

Interest is growing in developing conservation strategies to restore and maintain coral reef ecosystems in the face of mounting anthropogenic stressors, particularly climate warming and associated mass bleaching events. One such approach is to propagate coral colonies ex situ and transplant them to degraded reef areas to augment habitat for reef-dependent fauna, prevent colonization from spatial competitors, and enhance coral reproductive output. In addition to such "demographic restoration" efforts, manipulating the thermal tolerance of outplanted colonies through assisted relocation, selective breeding, or genetic engineering is being considered for enhancing rates of evolutionary adaptation to warming.

Glacier retreat creating new Pacific salmon habitat in western North America.

Glacier retreat poses risks and benefits for species of cultural and economic importance. One example is Pacific salmon (Oncorhynchus spp.), supporting subsistence harvests, and commercial and recreational fisheries worth billions of dollars annually.

Evolution and connectivity influence the persistence and recovery of coral reefs under climate change in the Caribbean, Southwest Pacific, and Coral Triangle.

Corals are experiencing unprecedented decline from climate change-induced mass bleaching events. Dispersal not only contributes to coral reef persistence through demographic rescue but can also hinder or facilitate evolutionary adaptation. Locations of reefs that are likely to survive future warming therefore remain largely unknown, particularly within the context of both ecological and evolutionary processes across complex seascapes that differ in temperature range, strength of connectivity, network size, and other characteristics.

Evolution reverses the effect of network structure on metapopulation persistence.

Global environmental change is challenging species with novel conditions, such that demographic and evolutionary trajectories of populations are often shaped by the exchange of organisms and alleles across landscapes. Current ecological theory predicts that random networks with dispersal shortcuts connecting distant sites can promote persistence when there is no capacity for evolution. Here, we show with an eco-evolutionary model that dispersal shortcuts across environmental gradients instead hinder persistence for populations that can evolve because long-distance migrants bring extreme trait values that are often maladaptive, short-circuiting the adaptive response of populations to directional change.

Y-chromosome haplotypes are associated with variation in size and age at maturity in male Chinook salmon.

Variation in size and age at maturity is an important component of life history that is influenced by both environmental and genetic factors. In salmonids, large size confers a direct reproductive advantage through increased fecundity and egg quality in females, while larger males gain a reproductive advantage by monopolizing access to females. In addition, variation in size and age at maturity in males can be associated with different reproductive strategies; younger smaller males may gain reproductive success by sneaking among mating pairs.

Glacier Retreat and Pacific Salmon.

Glaciers have shaped past and present habitats for Pacific salmon (Oncorhynchus spp.) in North America. During the last glacial maximum, approximately 45% of the current North American range of Pacific salmon was covered in ice.

Individual behavior drives ecosystem function and the impacts of harvest.

Current approaches for biodiversity conservation and management focus on sustaining high levels of diversity among species to maintain ecosystem function. We show that the diversity among individuals within a single population drives function at the ecosystem scale. Specifically, nutrient supply from individual fish differs from the population average >80% of the time, and accounting for this individual variation nearly doubles estimates of nutrients supplied to the ecosystem.

Resurgence of an apex marine predator and the decline in prey body size.

In light of recent recoveries of marine mammal populations worldwide and heightened concern about their impacts on marine food webs and global fisheries, it has become increasingly important to understand the potential impacts of large marine mammal predators on prey populations and their life-history traits. In coastal waters of the northeast Pacific Ocean, marine mammals have increased in abundance over the past 40 to 50 y, including fish-eating killer whales that feed primarily on Chinook salmon. Chinook salmon, a species of high cultural and economic value, have exhibited marked declines in average size and age throughout most of their North American range.

Does lipid-correction introduce biases into isotopic mixing models? Implications for diet reconstruction studies.

Carbon isotopes are commonly used in trophic ecology to estimate consumer diet composition. This estimation is complicated by the fact that lipids exhibit a more depleted carbon signature (δC) than other macromolecules, and are often found at different concentrations among individual organisms. Some researchers argue that lipids bias diet reconstructions using stable isotopes and should be accounted for prior to analysis in food web mixing models, whereas others contend that removing lipids may result in erroneous interpretations of the trophic interactions under study.

Effects of warming climate and competition in the ocean for life-histories of Pacific salmon.

The life-histories of exploited fish species, such as Pacific salmon, are vulnerable to a wide variety of anthropogenic stressors including climate change, selective exploitation and competition with hatchery releases for finite foraging resources. However, these stressors may generate unexpected changes in life-histories due to developmental linkages when species complete their migratory life cycle in different habitats. We used multivariate time-series models to quantify changes in the prevalence of different life-history strategies of sockeye salmon from Bristol Bay, Alaska, over the past half-century-specifically, how they partition their lives between freshwater habitats and the ocean.

Shifting habitat mosaics and fish production across river basins.

Watersheds are complex mosaics of habitats whose conditions vary across space and time as landscape features filter overriding climate forcing, yet the extent to which the reliability of ecosystem services depends on these dynamics remains unknown. We quantified how shifting habitat mosaics are expressed across a range of spatial scales within a large, free-flowing river, and how they stabilize the production of Pacific salmon that support valuable fisheries. The strontium isotope records of ear stones (otoliths) show that the relative productivity of locations across the river network, as both natal- and juvenile-rearing habitat, varies widely among years and that this variability is expressed across a broad range of spatial scales, ultimately stabilizing the interannual production of fish at the scale of the entire basin.

Isotopes in teeth and a cryptic population of coastal freshwater seals.

Human activities threaten the biodiversity of aquatic mammals across the globe. Conservation of these species hinges on the ability to delineate movements and foraging behaviors of animals, but gaining such insights is hampered by difficulties in tracing individuals over their lives. We determined isotope ratios in teeth ( Sr/ Sr, C/ C, and O/ O) to examine lifelong movement and resource-use patterns of a unique freshwater population of a wide-ranging pinniped species (harbor seal [Phoca vitulina]) that resides in Iliamna Lake, Alaska (U.

Recruitment variation disrupts the stability of alternative life histories in an exploited salmon population.

Males of many fish species exhibit alternative reproductive tactics, which can influence the maturation schedules, fishery productivity, and resilience to harvest of exploited populations. While alternative mating phenotypes can persist in stable equilibria through frequency-dependent selection, shifts in tactic frequencies have been observed and can have substantial consequences for fisheries. Here, we examine the dynamics of precocious sneaker males called "jacks" in a population of sockeye salmon () from Frazer Lake, Alaska.

The phenology of migration in an unpredictable world.

In Focus: Freshwater, C., Trudel, M., Beacham, T.

Spatial heterogeneity contributes more to portfolio effects than species variability in bottom-associated marine fishes.

Variance of community abundance will be reduced relative to its theoretical maximum whenever population densities fluctuate asynchronously. Fishing communities and mobile predators can switch among fish species and/or fishing locations with asynchronous dynamics, thereby buffering against variable resource densities (termed 'portfolio effects', PEs). However, whether variation among species or locations represent the dominant contributor to PE remains relatively unexplored.

An assessment of assumptions and uncertainty in deuterium-based estimates of terrestrial subsidies to aquatic consumers.

The deuterium ratio ( H/ H) in tissue is often used to estimate terrestrial subsidies to aquatic consumers because of strongly differentiated values between terrestrial and aquatic primary producers. However, quantitative deuterium-based analyses of terrestrial resource assimilation are highly dependent on several poorly defined assumptions. We explored the sensitivity of these estimates to assumptions regarding environmental water contributions to consumer deuterium content (ω) and algal photosynthetic hydrogen discrimination (ε ).

Who Should Pick the Winners of Climate Change?

Many conservation strategies identify a narrow subset of genotypes, species, or geographic locations that are predicted to be favored under different scenarios of future climate change. However, a focus on predicted winners, which might not prove to be correct, risks undervaluing the balance of biological diversity from which climate-change winners could otherwise emerge. Drawing on ecology, evolutionary biology, and portfolio theory, we propose a conservation approach designed to promote adaptation that is less dependent on uncertain predictions about the identity of winners and losers.