Spatial and environmental effects on Coho Salmon life history trait variation

Area of Science:

• Ecology
• Evolutionary Biology
• Fisheries Science

Background:

• Life history traits in widely distributed species are shaped by trade-offs between reproductive investment and environmental conditions.
• Coho salmon (Oncorhynchus kisutch) exhibit a broad geographic range, experiencing diverse environmental conditions across populations.

Purpose of the Study:

• To examine the effect of environmental variables on female size, egg size, fecundity, and reproductive investment in British Columbia Coho salmon populations.
• To understand how latitude, migration distance, temperature, and hydrologic features influence reproductive patterns.

Main Methods:

• Utilized an information theoretic approach to analyze data from Coho salmon populations across British Columbia.
• Investigated relationships between environmental variables (latitude, migration distance, temperature, river size, headwater source) and reproductive traits.

Main Results:

• Female size increased with latitude and decreased with migration distance.
• Egg size was influenced by intragravel temperature, migration distance, and river location relative to lakes.
• Fecundity varied with latitude, spawning temperature, river size, and river type (below lakes vs. tributary sources).
• Relative gonad size increased with latitude and decreased with migration distance.

Conclusions:

• Latitude, migratory distance, temperature, river size, and headwater source are key factors shaping Coho salmon reproductive investment, particularly egg size.
• The partitioning of gonadal mass indicates a trade-off between egg size and fecundity.
• Local optima for egg size, potentially driven by intragravel temperature, may explain variations in fecundity.