Abstract

Agricultural practices and urban development have altered streamflows within the Eastern Broadleaf Province of Minnesota. Stream-flow alteration can produce significant changes in native freshwater communities. Therefore, knowledge of streamflow effects on representative freshwater populations and communities within the province are needed to maintain ecological integrity. Fish community and population dynamics often display predictable responses to flow regimes, which can make fishes model organisms for examining flow-ecology relationships.

In lotic systems, annual variation in streamflow can influence the annual growth and recruitment of fishes. Understanding the growth and recruitment of fish populations is essential for management and conservation efforts. Growth can affect population size structure and sexual maturation, while recruitment can affect the abundance, and genetic diversity of a population.

Recruitment was quantified using studentized residuals from weighted catch-curve regressions as a measure of year-class strength. Relationships between annual streamflow magnitude and variability and the recruitment of the three species of interest were identified according to species-specific traits. I quantified the growth of Smallmouth Bass Micropterus dolomieu, Rock Bass Ambloplites rupestris, and Northern Hogsucker Hypentelium nigricans populations with mixed-effects growth models. Data from streams exhibiting growth-year effects were used to examine relationships between summer-high-flow duration and annual fish growth.

Little evidence was found for either long-term or short-term flow effects on recruitment during the adult spawning or juvenile rearing periods. The recruitment of nest-building and benthic-lithophilous fishes was not significantly related to long-term-spawning-period flow magnitude for the majority (i.e., 10 of 14) of streams, and was not significantly related to short-term-spawning-period flow magnitude at any of the 14 streams. Recruitment of fishes exhibiting cruiser, maneuverer, and benthic-hugger locomotion morphologies was not significantly related to long-term-rearing-period flow variability for the majority (i.e., 12 of 14) of streams, and was not related to short-term-rearing-period flow variability for any of the 14 streams. Growth was attributed to age and individual fish effects for 11 of the 28 fish populations among species. Most populations that exhibited growth-year effects among streams did not show a significant relationship between growth and the duration of summer-high flows (i.e., 4 of 11 populations).

Temperature regimes, as well as the timing, magnitude, and frequency of flows may have contributed to differences in the annual recruitment and growth of fishes among some of the streams in this study. However, minimal growth-year effects observed at the majority of my streams suggest that biotic factors (e.g., fish age, genetic differences) may play a large role in determining the growth rates of fishes within the streams studied.

Advisor

Shannon Fisher

First Committee Member

Douglas Dieterman

Second Committee Member

John Krenz

Date of Degree

2016

Language

english

Document Type

Thesis

Degree

Master of Science (MS)

Department

Biological Sciences

College

Science, Engineering and Technology

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

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