Fish Data
Fish abundance data were obtained from the “Fish electrofishing, gill netting, and fyke netting counts” dataset provided by the National Science Foundation’s National Ecological Observatory Network (NEON 2020). This dataset contains stream fish abundances as well as abiotic data including environmental, geographic, and sampling design factors (e.g., date of sampling, water temperature, dissolved oxygen, latitude) and biotic data (e.g., fish length, fish weight) for 28 aquatic monitoring locations across the United States. Our analysis used samples from 2016–2019 collected twice per year per location, in Fall and Spring across subsequent days for 39 species—36 species in the Fall and 35 species in the Spring.
The abundance dataset contained taxonomic information, but samples varied on the level of identification. We restricted our analyses to species with species-level identification as we were concerned that a higher taxonomic grouping would obscure key biological interactions. We excluded samples from the analysis if environmental conditions were not recorded. Additionally, as sampling locations were established at different times, and not all locations had the same number of sampling observations, we removed sites that had less than seven sampling seasons to improve model convergence. Ultimately, we used nine sites that spanned the United States (Figure 1).
For our trait analysis, we obtained species-specific traits, such as longevity, and large river preference from Fishtraits (Frimpong & Angermeier 2009) and obtained species’ maximum length and maximum weight from the NEON dataset containing the samples used to construct our networks. Fishtraits is an extensive database that contained traits for our species except for Etheostoma lachneri , which we supplemented with those of Etheostoma raneyi , a close relative (Ross 2012). Furthermore, we obtained feeding behaviour information from NatureServe (NatureServe 2020) where fish were classified as belonging to one of the following non-exclusive categories: (i) non-feeder (non-parasitic lamprey species), (ii) herbivore, (iii) insectivore, and (iv) piscivore.