April 13, 2026

Friday Seminar Spotlight: Kelsey presents her Master’s research on Arctic Char behavior!

Last Friday, our department had the pleasure of hearing Kelsey present her Master’s research. Kelsey is a Master’s student from the Department, where she is conducting her Master’s research under the supervision of Stefán.
She delivered a presentation of her project titled: “Effects of prey distribution on resource defense, foraging behavior, and growth in stream-dwelling Arctic Char (Salvelinus alpinus)”. 
This talk was part of her final preparation ahead of her upcoming thesis defense, which will take place very soon. It was a great opportunity to share her work with the department, and receive valuable feedback in a supportive seminar setting. 
For this particular talk, Sabine—another student from the department who organize the Friday Seminar series—kindly brought refreshments for the event, adding a welcoming and friendly touch to the occasion.

​If you are interested in our Friday Seminars, you can find more information and previous talks here: Seminar series

About the study:
Animals exhibit variable competitive strategies in response to the distribution of critical resources, ranging from indirect interactions during resource depletion (i.e., exploitative competition) to direct attacks and monopolization (i.e., interference competition). Spatial distribution of drifting prey provides a unique form of resource heterogeneity that may shape resource defense, foraging, and growth in stream salmonids.
Kelsey conducted a field experiment on Arctic char Salvelinus alpinus in a small Icelandic stream to test different spatial distributions of drifting invertebrate prey. Specifically, ninety-six individually-tagged juvenile Arctic char, placed in twelve stream enclosures for one month, were subjected to upstream flow manipulations that yielded invertebrate drift either evenly distributed (dispersed) or unevenly distributed (clumped) in space. Observers recorded repeated individual estimates of activity, spatial location, aggression, and foraging behavior. Body size was measured to estimate growth rates and predict dominance status.
Fish aggregated more in the clumped prey treatment, where larger, dominant individuals monopolized the concentrated resource patch and excluded subordinate fish. Aggression was more pronounced (attack rate ~60% higher) in the clumped versus the dispersed prey scenario. Furthermore, in the clumped treatment, dominant fish exhibited a sedentary foraging tactic whereas subordinates searched more widely for prey. Mean growth rate did not differ between treatments, but surprisingly, larger fish grew slower in the clumped than in the dispersed treatment.
Overall, the study extends resource defense theory to invertebrate drift, a rapidly renewing food resource, and shows that flow alteration can redistribute this resource, shifting competitive structure and growth patterns in drift-feeding fish.

Congratulations to Kelsey for a clear, engaging, and high-quality presentation. We are all looking forward to her upcoming thesis defense and wish her the very best in the final steps of her Master’s journey!

By M. Delbasty
Study abstract by Kelsey Stansberry