Thesis
Carrying capacity: a concept for guiding Brook Trout stocking on Owhi Lake, WA
Washington State University
Master of Science (MS), Washington State University
05/2016
Handle:
https://hdl.handle.net/2376/104401
Abstract
Fisheries managers are often tasked with balancing stocking rates with population dynamics—determining local fish population size relative to habitat and resource availability. Similar to other systems, Owhi Lake has experienced inconsistent stocking regimes without evaluating their effectiveness. In order to evaluate stocking effectiveness, we estimated a seasonal baseline carrying capacity for Brook Trout (Salvelinus fontinalis) in Owhi Lake, WA. Owhi Lake provides an excellent test case for carrying capacity as Brook Trout is the only harbored fish species. Previous studies have quantified their prey consumption, including crayfish, macroinvertebrates, and zooplankton. We used bioenergetics modeling to identify Trout energy requirements and monitored dissolved oxygen and temperature variations using water profiles to quantify available habitat. To quantify prey availability, crayfish were collected using minnow traps and SCUBA surveys. Zooplankton densities were quantified using profile collections; littoral invertebrates were quantified using D-frame kick nets. We measured total available energy using prey densities and caloric values to evaluate short-term carrying capacity of the lake, and results were coupled with fish condition indices to compare with measured surpluses/deficits. We found multiple seasonal prey biomass deficits, especially water boatman and scud, by comparing prey availability to Brook Trout consumption. We also found that fish younger than age-4 had better condition than fish older than age-4, suggesting that density-dependent factors are contributing to an overall decrease in older Brook Trout condition. Since we identified seasonal prey deficits, it is likely that prey availability may be a factor impairing older Brook Trout condition.
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Details
- Title
- Carrying capacity
- Creators
- Timothy Nathanial Taylor
- Contributors
- Barry C. Moore (Chair)Gary H Thorgaard (Committee Member) - Washington State University, Biological Sciences, School ofStephen L Katz (Committee Member) - Washington State University, Environment, School of the (CAS)
- Awarding Institution
- Washington State University
- Academic Unit
- Agricultural, Human, and Natural Resource Sciences, College of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Number of pages
- 113
- Identifiers
- 99900525121701842
- Language
- English
- Resource Type
- Thesis