Earlier migration timing, decreasing phenotypic variation, and biocomplexity in multiple salmonid species

Area of Science:

• Ecology
• Climate Change Biology
• Evolutionary Biology

Background:

• Phenological shifts driven by climate change can alter population dynamics and ecological interactions.
• Long-term demographic data are crucial for understanding these climate-driven phenomena.
• Salmonid populations face challenges due to changing environmental conditions.

Purpose of the Study:

• To investigate the consistency of phenological patterns and their drivers across salmonid species and life histories.
• To determine if phenological shifts are linked to changes in phenotypic variation.
• To assess how phenological changes affect the availability of salmon as a resource subsidy.

Main Methods:

• Utilized a multi-decade census of five salmonid species (14 life histories) in an Alaskan stream.
• Analyzed temporal trends in migration timing and intra-annual phenotypic variation.
• Examined the influence of freshwater temperature on migration patterns.

Main Results:

• Freshwater temperature significantly influences salmonid migration timing, with events occurring earlier (1.7 days/decade) and over shorter durations (1.5 days/decade).
• Phenological shifts were not correlated with changes in intra-annual phenotypic variation, indicating independent responses.
• Despite stable adult populations, the temporal availability of salmon as a freshwater resource has decreased by nearly 30 days since 1971.

Conclusions:

• Climate change is driving significant phenological shifts in salmonid migration timing.
• These shifts, while not directly impacting adult population stability, reduce resource availability for other species.
• Understanding these complex ecological responses is vital for predicting future ecosystem dynamics.