Graduation Date
Summer 2021
Document Type
Thesis
Program
Master of Science degree with a major in Natural Resources: option Environmental Science and Management
Committee Chair Name
Alison O'Dowd
Committee Chair Affiliation
HSU Faculty or Staff
Second Committee Member Name
Nicholas Som
Second Committee Member Affiliation
HSU Faculty or Staff
Third Committee Member Name
Darren Ward
Third Committee Member Affiliation
HSU Faculty or Staff
Subject Categories
Environmental Science and Management
Abstract
The widespread construction of dams to regulate rivers has dramatically altered aquatic ecosystems, but these impoundments also provide a unique opportunity to support freshwater conservation goals by implementing functional flow regimes designed to mitigate dam-related impacts on fisheries. Drifting invertebrates are an important food source for stream-dwelling juvenile salmonids such that drift feeding can be an energetically profitable foraging strategy, yet the effect of streamflow alterations on invertebrate drift dynamics is largely undetermined. Drift net samples were collected on four days before and four days during the ascending limb (14-42 m3/s) of restoration pulse flows in April 2020 at four sites located along 48 river kilometers of the Trinity River downstream of Lewiston Dam in northern California. Results provide evidence of an inconsistent response by drifting invertebrate biomass concentration (mg/m3) across pulse flows with increases observed during the first pulse, but little effects or potential decreases in subsequent pulses. Drift response varied among sites, where the effect of pulse flows was greater at sites closer to the dam and that underwent longer durations without disturbance in the preceding months. Weighted mean length (mm) of drifting invertebrates was lower at higher flows, a trend that may be temporally driven by differing aquatic or terrestrial taxonomic groups dominating during base or pulse flows. These findings suggest that dam-release restoration flows can temporarily increase prey availability in the drift for juvenile salmonids, but the exploration of alternative restoration flow actions with meaningful long-term benefits to salmonid populations may be a more beneficial solution.
Citation Style
Journal of Environmental Management
Recommended Citation
Williamshen, Jasmine S., "Response of invertebrate drift to dam-release restoration pulse flows from Lewiston Dam on the Trinity River, CA" (2021). Cal Poly Humboldt theses and projects. 505.
https://digitalcommons.humboldt.edu/etd/505