Date of Award:

5-2016

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Committee Chair(s)

Brett Roper

Committee

Brett Roper

Committee

Phaedra Budy

Committee

Karen H. Beard

Abstract

Rivers are often managed without informed knowledge of how sportfish use different areas of the river to reproduce, and rarely take into account the relationship between fish movement and how they are distributed within the river when making management decisions. The population of native Bonneville cutthroat trout (Oncorhynchus clarki utah) within the Logan River is the largest documented population remaining for this imperiled species, and still maintains extremely high numbers of fish in the upper river. Currently, fishing is not allowed in the upper 20 kilometers of the Logan River watershed during spawning, based on the assumption that cutthroat trout migrate to and spawn primarily in this section. I redetected cutthroat trout tagged (2,271) during years 2008-2012 in seven mainstem and tributary reaches of the Logan River during spawning months (April-June) of 2013 using a combination of stationary and mobile techniques. Most cutthroat trout in both mainstem and tributary reaches spawn near to their original tagging site; however, small numbers of trout moved long distances to seek out spawning sites throughout the watershed. Growth, length, and fitness estimates between mobile and non-mobile tagged fish demonstrate that while mobile fish tend to growth faster, be slightly larger, and in some cases be in relatively poorer condition, these differences appear inconsequential and depend on the location within the watershed. A genetic analysis conducted on trout sampled from each study site confirms this is one population (instead of many small populations). Using River Styles® to assess unique types of river reaches, I created a large-scale population estimate of spawning individuals, which found approximately 61% of spawning cutthroat trout are not subject to angling during the spawning season, while 39% could be susceptible to harvest in the lower basin and its tributaries. This indicates that future conservation efforts should promote risk-averse management throughout the watershed, rather than focus heavily on any one section of the river in order to protect this species for public enjoyment for future generations.

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