Document Type

Thesis - Open Access

Award Date

2022

Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

Steven Chipps

Abstract

Because return to angler is an important outcome of put-and-take fisheries, understanding mortality of stocked Rainbow Trout is fundamental to managing these fisheries. Harvest rates of stocked Rainbow Trout Oncorhynchus mykiss in the Black Hills of South Dakota are believed to be below management objectives. Rainbow Trout not harvested by anglers are assumed to be lost to various sources of mortality, raising concerns about the cost of the Rainbow Trout stocking program relative to the benefit provided to anglers. (Simpson 2008). This study evaluated the factors influencing mortality of Rainbow Trout stocked into Black Hills reservoirs. We assessed the effects of angling, environmental conditions, stress, and diet on mortality of stocked Rainbow Trout. We conducted this study on four small reservoirs (~1-10ha) in the Black Hills between 2018 and 2019. Using creel surveys, we determined harvest rate and expected angling mortality based on angling type. We measured environmental variables to determine how habitat suitability for Trout varied spatially and temporally within and among reservoirs. We assessed stress levels in Rainbow Trout using three common physiological indicators found in blood plasma that included cortisol concentration, glucose, and lactate. We evaluated stomach contents to assess the timing and use of natural prey sources by stocked Rainbow Trout. Using an information theoretic approach, we developed models that best explain how biological and environmental factors influence mortality of stocked Rainbow Trout. Estimated angling-related mortality for Rainbow Trout during the study was relatively high at 78% (15,497) and ranged from 42% to 80% among reservoirs. Harvest by anglers was the greatest source of mortality, with an estimated 56% (11,071) of the 19,900 Rainbow Trout harvested by anglers. Catch-and-release angling was the second largest source of mortality with 22% (4,426) of stocked Rainbow Trout lost to catch-andrelease mortality. Estimated catch-and-release mortality ranged from 11 to 30% among study reservoirs. Both harvest and catch-and-release mortality were reliably predicted by environmental and biological parameters. Based on AIC analysis, our top candidate models explained 80% of the variation in harvest mortality of Rainbow Trout and 85% of the variation in catch-and-release mortality.

Number of Pages

83

Publisher

South Dakota State University

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Rights Statement

In Copyright