Degree
Doctor of Philosophy (PhD)
Department
Oceanography and Coastal Sciences
Document Type
Dissertation
Abstract
In this work I investigate several facets of stream fish ecology at large spatial scales. In this dissertation, I use a dataset of over a million stream fish observations across the continental United States to explore patterns of abundance for broadly distributed stream fish, how regional base flow influences local scale flow-ecology relationships, and how connectivity influences stream fish diversity in coastal river drainages. I test the abundant-center hypothesis (ACH), which posits that species are most abundant at the center of their range, and abundance monotonically declines from the center to edge of the range, and propose an alternative macroscale pattern of abundance, multi-core distributions, that apply to dispersal limited taxa such as stream fish. I then test if range and body size are related to the number of abundant cores, a geographic area of elevated abundance. I investigate if regional base flow modulates local flow-ecology relationships through cross-scale interactions. Base flow is an important, but understudied, part of flow regimes regarding stream fish diversity. Last, I use a measure of network connectivity to test if streams with greater degrees of connectivity are positively associated with taxonomic diversity, functional diversity, and functional redundancy. Connectivity is inherently important to stream fish life histories, but evidence potentially linking river network structure to patterns of diversity is sparse. The results of the ACH test suggested very little support for the ACH. Of studied species, 43 species exhibited multi-core distributions and 21 exhibited single-core distributions. Furthermore, range size was positively correlated to the number of abundant cores in species ranges. I built Bayesian hierarchical models that revealed regional base flow variability at the ecoregion-III scale had a positive effect on local flow-ecology relationships. Greater variability of base flow in an ecoregion indicates a greater variety in flow regimes that select for different stream fish communities yielding greater taxonomic and functional diversity. The regional effect of base flow highlights how regional scale processes can influence local scale relationships through cross-scale interactions. Last, I demonstrate that greater degrees of connectivity are positively associated with function diversity and redundancy in certain hydrologic stream classes.
Date
7-14-2025
Recommended Citation
Zink, Matthew L., "Stream Fish Ecology at the Macroscale: Abundance, Base Flow, and Connectivity" (2025). LSU Doctoral Dissertations. 6863.
https://repository.lsu.edu/gradschool_dissertations/6863
Committee Chair
Midway, Stephen R.
DOI
10.31390/gradschool_dissertations.6863