Date of Award


Publication Type


Degree Name



Earth and Environmental Sciences


Fish migration;Food webs;Isoscapes;Rivers;Spatial Stream Network models;Stable isotopes


Aaron Fisk


Gregory Jacobs



Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.


Great Lakes tributaries are undergoing major ecosystem restoration through dam removal aimed at improving habitat connectivity. Re-establishing connectivity can have consequences for both desirable and undesirable species, especially in watersheds that risk the invasion of non-native species. To predict and evaluate the effects of reconnecting native fish habitats, I used stable isotopes of carbon (δ13C), nitrogen (δ15N), and sulphur (δ34S), spatial stream network (SSN) models and trophic niche measurements to examine the influence of land cover and nutrient concentration on the trophic ecology and distribution of stable isotopes of biofilm, macroinvertebrates, and fishes in the Boardman/Ottaway River (BOR), a tributary to Lake Michigan prior to restoring fishes migratory routes. At the whole river systems scale, spatial autocorrelation was strong for biofilm δ13C and δ15N, habitat heterogeneity was strong for macroinvertebrate δ13C and δ15N, and the mayfly δ34S did not fit a pattern. Streams with high NH4 levels had low trophic redundancy but high trophic diversity indicating consumers differentiate their resources and ecological roles demonstrating a bottom-up control on food webs. At many sites, macroinvertebrate had δ13C values lower than terrestrial or instream carbon sources, suggesting assimilation of methane-oxidizing bacteria occurs in the BOR. My work provides novel understanding of the strength of land cover drivers and nutrient levels on δ13C, δ15N, and δ34S and food web structure at a fine spatial scale and acts as a foundation for future food web monitoring after fishes’ migration is restored in the BOR.