Document Type

Report

Publisher

Utah State University

Publication Date

2022

First Page

1

Last Page

21

Abstract

Summer base flows for rivers are critical for maintaining water quality, healthy fish populations, and a functional aquatic ecosystem. Low summer base flows can increase water temperatures and lower dissolved oxygen levels. These conditions can cause Brown Trout (Salmo trutta) energetic stress and result in lower angler catch. The goal of this study was to determine if low river flows and higher water temperatures influence angler catch rates of Brown Trout on the lower Logan River, Utah and to better understand angler use of the lower river. We performed a creel survey on approximately 6.4 km of the lower Logan River from 1 April to 31 October 2019 to calculate mean monthly angler catch rates. We used continuous collection of stream temperature and flow from a river gage within the survey reach to calculate monthly means. Total Brown Trout caught were 1,481 and total angling effort was 2,147 hours for an overall catch rate of 0.7 fish per hour (fph) for the survey period. The highest angler catch rate (1.2 fph) was in June with the highest mean monthly discharge (16 m3/s) and a mean monthly water temperature of 9.6 °C. The lowest angler catch rate (0.41 fph) occurred in September with a mean monthly discharge of 2.12 m3/s and a mean monthly water temperature of 11.2°C. We found a positive correlation between flow rates and angler catch rates (R2 = 0.37), and a negative correlation between water temperatures and angler catch rates (R2 = 0.42), although neither were statistically significant. Our data suggest that even on a higher-than-average runoff year, angler success is impacted by low summer base flows. Maintaining increased river flow during typical summer low-flow time periods could increase angler catch rates and, ultimately, provide even greater satisfaction with this fishery. We also determined educational signage and outreach could be extremely influential, as anglers knew little about regulations of the fish community in general.

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