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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

Steven Chipps


Lake Trout Salvelinus namaycush were originally stocked into Pactola Reservoir, South Dakota in the late 1970s and became a primary management species by the early 2000s. In recent years, evidence for natural reproduction of the Lake Trout population has emerged, along with observations of low body condition and few fish above the minimum harvest size of 610 mm. Illegal introductions of Northern Pike Esox lucius in Pactola Reservoir may further complicate salmonid management, with declining returns to anglers and reduced abundance of Rainbow Trout Oncorhynchus mykiss since 2006. The objectives of this study were to quantify population characteristics of Lake Trout and Northern Pike, quantify annual prey consumption, and evaluate the influence of harvest regulations on Lake Trout using a life-history model. Lake Trout and Northern Pike were sampled from 2012 to 2013. Seasonal diets and bioenergetics analysis were used to quantify consumption by Lake Trout and Northern Pike. A life-history model was used to model effects of potential harvest regulations. The main forage species for Lake Trout were Rainbow Smelt Osmerus mordax and Bluegill Lepomis machrochirus. Juvenile Lake Trout consumed invertebrates, centrarchids, and Rainbow Smelt. Adult Lake Trout consumed primarily Bluegill and Rainbow Smelt. Lake Trout condition was comparable among years (mean Wr=90; SD=11). Annual surveys since 2003 showed relatively constant catch per unit effort of Lake Trout. Based on the Lake Trout yield models, I concluded that current harvest regulations fit existing management goals. The 610 mm minimum size limit will better withstand future increases in fishing effort than more liberalized size and harvest regulations. Northern Pike diets mainly consisted of centrarchids, Rainbow Smelt, and Rainbow Trout. Northern Pike consumption of Rainbow Trout increased with size of Northern Pike. Individual, small Northern Pike consumed 0.0 to 1.2 Rainbow Trout y-1, whereas large Northern Pike (≥600 mm) consumed 10.3 to 23.4 Rainbow Trout y-1. In general, diet overlap between Lake Trout and Northern Pike was low (mean overlap M=0.43; SD=0.24), owing to differences in habitat use. Large Northern Pike are a primary source of post-stocked mortality on Rainbow Trout. Efforts to mitigate predation losses should include the reduction of Northern Pike in Pactola Reservoir and decreasing the vulnerability of stocked Rainbow Trout.

Library of Congress Subject Headings

Lake trout -- South Dakota -- Pactola Reservoir Pike -- South Dakota -- Pactola Reservoir Fish populations -- South Dakota -- Pactola Reservoir Fishery management -- South Dakota -- Pactola Reservoir


Includes bibliographical references



Number of Pages



South Dakota State University



Rights Statement

In Copyright