Output of reproductive niche model generated for resident sockeye in Alouette Lake. Photo credit: Steven Brownlee

Alouette Lake salmon niche modeling

Output of reproductive niche model generated for resident sockeye in Alouette Lake. Photo credit: Steven Brownlee

Alouette Lake salmon niche modeling

I worked with Dr. Scott Hinch and Allison Hebert in developing a reproductive niche model for a rare ecotype of sockeye salmon (Oncorhynchus nerka) in BC’s Alouette Lake. Alouette Lake was dammed as part of a hydroelectric power project, and this damming event trapped a population of previously-anadromous sockeye salmon in the lake, leading to the development of a new deepwater-spawning ecotype. The goal of the project was to identify the habitat variables that the rare ecotype uses to select spawning habitat in the deep portions of the lake. To that end bathymetry, visual substrate composition transects across the lake and most importantly georeferenced spawning occurrences were collected. In consultation with the two project leads and technical advisors in the MGEM program I built a series of whole-lake substrate composition rasters and proxies for indicator variables like groundwater intrusion, and used them in concert with the suitability modeling software MaxEnt to construct a reproductive niche model for the ecotype.

This new deepwater ecotype has persisted into the 21st century, but new management plans have allowed for the release of juvenile sockeye downstream for the first time, causing the released fish to revert to their ancestral anadromous ecotype. These reverted anadromous sockeye are being transported back into the lake by management authorities, raising the possibility of the newcomers mating with the deepwater ecotype. Using hydroacoustic tracking data of the released anadromous sockeye I have also developed a second niche model for the spawning preferences of the anadromous sockeye and using comparative niche metrics have found that the anadromous sockeye and deepwater sockeye have significantly different reproductive niche envelopes, despite being released into the same ancestral habitat and sharing a very recent point of divergence.

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Steven Brownlee
Student in the Master of Geomatics for Environmental Management program