Resource allocation among arctic char in closed arctic lakes:

In closed arctic lakes, we observe a strong cycle in population structure in arctic char (Salvelinus alpinus) while population abundance remains generally stable.  We hypothesized this cycle was driven by strong internal density dependence that could operate via:

1. Food limitation including cannibalism, and/or
2. Size-based niche differentiation. 

We tested these hypotheses using a long time series of population data, as well as diet analyses and isotope-based trophic position and overlap in three different arctic lakes, Alaska.   We observed little evidence of cannibalism; however, other work has shown that cannibalism can be extremely influential even at very low levels (< 5%), yet extremely difficult to detect.  Furthermore, large and small adult char exhibited spatial niche differentiation; large char (> 300 mm) switched to a more littoral foraging pattern, incorporating a large proportion of snails in their diet relative to small (< 300 mm), pelagic adults. A better understanding of the processes regulating these populations will be critical in predicting the effects of climate change and in contributing to synthetic evaluations across arctic ecosystems.