Document Type

Thesis - Open Access

Award Date

2016

Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

Steven R. Chipps

Keywords

abundance, predation, rainbow trout, recruitment, survival, wild trout

Abstract

Rainbow Trout Oncorhynchus mykiss are routinely stocked in Black Hills streams and reservoirs to enhance angling opportunities for the public, however in most cases, hatchery-reared Rainbow Trout do not successfully recruit to establish natural populations. One exception is the Deerfield Reservoir system, where it is estimated that up to 25% of the Rainbow Trout population consists of naturally produced, wild Rainbow Trout. While recruitment of wild Rainbow Trout to the Deerfield Reservoir fishery does occur, annual stockings of 12,000 hatchery Rainbow Trout have continued. In recent years, adipose fin clips were used to identify hatchery Rainbow Trout stocked into Deerfield Reservoir, however the personnel and time requirements of fin clipping resulted in the termination of fin clips in May 2014. An elimination or reduction of hatchery stockings may be considered in the future management of the Deerfield Reservoir Rainbow Trout population, however a lack of knowledge regarding factors such as predation, movement and emigration patterns, relative abundance, and apparent survival of wild Rainbow Trout has generated a need for additional research in order to help guide future management decisions. In addition, the termination of fin clipping requires the identification and evaluation of new techniques for the classification of wild and hatchery Rainbow Trout in Deerfield Reservoir. Thus the objectives of our research were to 1) investigate the predation on young Rainbow Trout and the diet composition of fishes in Deerfield Reservoir, 2) quantify the relative abundance, growth, and apparent survival of wild Rainbow Trout in the Deerfield Reservoir system, 3) describe the movement patterns and emigration rates of wild Rainbow Trout from tributary streams into Deerfield Reservoir, and 4) evaluate the use of stable isotope analysis and otolith microchemistry for the classification of wild and hatchery Rainbow Trout origins. Juvenile Rainbow Trout were not found in the diets of Rock Bass Ambloplites rupestris, Yellow Perch Perca flavescens, and adult (>200 mm) Rainbow Trout in Deerfield Reservoir and indicated that the risk of predation upon Rainbow Trout is negligible. The diet composition of all species consisted primarily of aquatic invertebrates and dietary overlap did exist among Rainbow Trout, Yellow Perch, and Rock Bass. While diets were similar among species with regard to aquatic invertebrate prey, the degree of diet overlap with Rainbow Trout was generally low (range 0.2- 0.57). We found that the relative abundance of wild Rainbow Trout in tributary streams was greater in South Fork Castle Creek than in Castle Creek. Rainbow Trout movement and emigration from tributaries into Deerfield Reservoir was monitored in both tributaries using 12 mm passive integrated transponder (PIT) tags which showed that within and among stream movement was minimal throughout our study. We tagged 380 Rainbow Trout and in subsequent sampling events recaptured 81 unique fish using backpack electrofishing. Of these 81 fish only 3 were recaptured outside of the 100 m site in which they were tagged, resulting in 96% fidelity to original tagging site. Out of the total 380 tagged Rainbow Trout, another 73 (19%) unique fish were detected by an instream passive PIT tag reader emigrating from tributary streams into Deerfield Reservoir. We constructed a Von Bertalanffy growth model for wild Rainbow Trout in Deerfield Reservoir based on length frequency analysis and found that growth of fish up to age 4 was relatively slow in comparison to other populations, reaching only 210 mm by age 4. Using the growth parameters from the Von Bertalanffy growth model, we estimated survival of wild Rainbow Trout in the Deerfield Reservoir system to be as low as 3% during the first year of life. However, survival increased with each year of life, with relatively high survival (up to 66%) by age 4. In the absence of fin clips, identifying future trends in the wild Rainbow Trout population in Deerfield Reservoir requires the accurate classification of both wild and hatchery origins. Using stable isotope analysis we found that wild Rainbow Trout can be classified with greater than 75% accuracy using pectoral fin tissue, and greater than 85% accuracy using dorsal muscle tissue. We also used otolith microchemistry to identify the natal tributary stream origins of 9 wild Rainbow Trout collected in Deerfield Reservoir. Our results showed that 56% of wild Rainbow Trout in Deerfield Reservoir were classified to Castle Creek, while 44% were classified to South Fork Castle Creek. These results indicate that Castle Creek likely contributes a slightly greater number of wild Rainbow Trout recruits to the Deerfield Reservoir population than South Fork Castle Creek. Overall our results indicate a healthy, sustainable population of wild Rainbow Trout in Deerfield Reservoir. Our analysis of survival, abundance, and emigration data, as well as low risks of predation suggest that management of Deerfield Reservoir for wild Rainbow Trout in the absence of stocking or at reduced stocking rates is likely sustainable. Managing Deerfield Reservoir primarily for wild Rainbow Trout may be viable, however fisheries managers should consider the impact of reduced stockings on angler catch rates. In addition, a reduction or elimination of hatchery stockings would likely have positive impacts on the wild Rainbow Trout population and monitoring changes in the population dynamics of wild Rainbow Trout would be beneficial to the assessment of any stocking changes.

Library of Congress Subject Headings

Rainbow trout -- South Dakota -- Deerfield Reservoir

Fish populations -- South Dakota -- Deerfield Reservoir

Predation (Biology) -- South Dakota -- Deerfield Reservoir

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

97

Publisher

South Dakota State University

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Rights Statement

In Copyright