Julien Beaulieu - PhD candidate

Consequences of fisheries-induced changes in fish population demography, food web structure, and aquatic ecosystem function

My research is looking at the consequences of fish population demographic changes induces by fisheries on food web structure and ecosystemic functions, and develops molecular tools allowing cost-effective fish population demography estimates. My thesis is part of a large collaborative project including a whole ecosystem experiment where invasive brook trout (S. fontinalis) populations were size-selectively harvested in head lakes from the Canadian Rockies. We found that applying mass-balance and bioenergetic to environmental DNA (eDNA) allows population size estimates as good as mark-recapture methods, and that environmental RNA outperforms eDNA when using simple modelling approaches. The rest of my project detangles how these detected changes in fish population demography impact food web structure, nutrient cycles and lake metabolism via changes in diet, top-down pressure and nutrient excretion. My thesis will provide an integrated synthesis of the links between different levels of ecological organisation in addition to develop the tools necessary for population demography studies in freshwater.

Cosupervised with Melania Cristescu, Department of Biology, McGill