Source Themes

Kings of the North Bridging Disciplines to Understand the Effects of Changing Climate on Chinook Salmon in the Arctic–Yukon–Kuskokwim Region

Understanding how species are responding to environmental change is a central challenge for stewards and managers of fish and wildlife who seek to maintain harvest opportunities for communities and Indigenous peoples. This is a particularly daunting but increasingly important task in remote, high-latitude regions where environmental conditions are changing rapidly and data collection is logistically difficult. The Arctic–Yukon– Kuskokwim (AYK) region encompasses the northern extent of the Chinook Salmon Oncorhynchus tshawytscha range where populations are experiencing rapid rates of environmental change across both freshwater and marine habitats due to global climate change. Climate–salmon interactions in the AYK region are a particularly pressing issue as many local communities have a deep reliance on a subsistence way of life. Here, we synthesize perspectives shared at a recent workshop on Chinook Salmon declines in the AYK region. The objectives were to discuss current understandings of climate–Chinook Salmon interactions, develop a set of outstanding questions, review available data and its limitations in addressing these questions, and describe the perspectives expressed by participants in this workshop from diverse backgrounds. We conclude by suggesting pathways forward to integrate different types of information and build relationships among communities, academic partners, and fishery management agencies.

Delayed trophic response of a marine predator to ocean condition and prey availability during the past century

Understanding the response of predators to ecological change at multiple temporal scales can elucidate critical predator–prey dynamics that would otherwise go unrecognized. We performed compound-specific nitrogen stable isotope analysis of amino acids on 153 harbor seal museum skull specimens to determine how trophic position of this marine predator has responded to ecosystem change over the past century. The relationships between harbor seal trophic position, ocean condition, and prey abundance, were analyzed using hierarchical modeling of a multi-amino-acid framework and applying 1, 2, and 3 years temporal lags. We identified delayed responses of harbor seal trophic position to both physical ocean conditions (upwelling, sea surface temperature, freshwater discharge) and prey availability (Pacific hake, Pacific herring, and Chinook salmon). However, the magnitude and direction of the trophic position response to ecological changes depended on the temporal delay. For example, harbor seal trophic position was negatively associated with summer upwelling but had a 1-year delayed response to summer sea surface temperature, indicating that some predator responses to ecosystem change are not immediately observable. These results highlight the importance of considering dynamic responses of predators to their environment as multiple ecological factors are often changing simultaneously and can take years to propagate up the food web.

Recent divergent changes in Alaskan pinniped trophic position detected using compound-specific stable isotope analysis

We evaluated how trophic position of harbor seals and Steller sea lions has changed from the 1950s-2010s regional, decadal scales using a Bayesian hierarchical analysis using stable isotope data derived from historic harbor seal bone specimens.

Stable isotope signatures in historic harbor seal bone link food web‐assimilated carbon and nitrogen resources to a century of environmental change

We evaluated how ocean conditions influence the assimilation of nitrogen and carbon into coastal marine food webs y analyzing a century of newly acquired molecular isotope data derived from historic harbor seal bone specimens.

Riparian soil nitrogen cycling and isotopic enrichment in response to a long‐term salmon carcass manipulation experiment

We measured the contribution of Pacific salmon to nitrogen transformations and concentrations to riparian boreal soils.

How commercial fishing effort is managed

We assessed approaches that managers use to sustain stocks on ecological, economic, and community-level outcomes.

A novel method for modeling age and length selectivity of sockeye salmon as applied to the Bristol Bay Port Moller test fishery

We developed a method for assessing length and residual program selectivity for Port Moller test fishery.