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Document Type

Thesis - University Access Only

Award Date

1990

Degree Name

Master of Science (MS)

Department

Wildlife and Fisheries Science

First Advisor

Charles G. Scalet

Keywords

diploid, triploid, rainbow trout, south dakota

Abstract

Triploid fish theoretically may divert energy from sexual development and reproductive behavior into somatic growth. Laboratory studies have indicated that juvenile triploids tend to be smaller, then surpass diploids after sexual maturation. The purpose of this study was to evaluate the lengths, weights, relative weights (Wr), survival, and gonadosomatic indices (GSI) of triploid and diploid rainbow trout Oncorhynchus mykiss in natural systems. In May 1987, a-month old triploid and diploid rainbow trout were stocked in equal proportions into six ponds (1.0 - 2.5 hectares). Drought eliminated rainbow trout populations in three ponds. Juvenile fish were sampled at the time of stocking and in the fall 1987. Adult fish were sampled in the fall 1988 and the springs of 1989 and 1990. Mean total lengths of juvenile triploids were significantly (P≤0.05) greater at the time of stocking in Iverson and Kinsley ponds. In the fall 1987, mean lengths and weights of triploid fish were larger, though not significantly (P>0. 05). Upon reaching adulthood, triploid lengths, weights, and Wr were less than those of diploids. Mean total lengths of triploids were significantly (P≤0.05) less in Iverson Pond in 1988, 1989, and 1990; in Kinsley Pond in 1990; and in Ray Pond in 1989. Mean weights of triploids were significantly (P≤0.05) less in Iverson Pond in 1988 and 1989; in Kinsley Pond in 1990; and in Ray Pond in 1989. Relative weights for triploids were significantly (P≤0.05) less in Iverson Pond in 1988 and in Ray Pond in 1988, 1989, and 1990. The GSI was significantly (P≤0.05) less for triploid females in Iverson Pond during 1989 and 1990, and in Ray Pond in 1989. Triploid fish never significantly (P>0. 05) outperformed diploids in length, weight, or Wr. Although survival did not lend itself to statistical analysis, catches of triploids were always less, suggesting lower survival. A morphometric and meristic evaluation indicated no differences in body shape or form between diploid and triploid fish. These data suggest that the use of triploid rainbow trout as a management option, at least under South Dakota pond conditions, is not justified as a means of obtaining increased growth.

Library of Congress Subject Headings

Rainbow trout -- South Dakota -- Genetics
Rainbow trout -- South Dakota -- Development
Polyploidy
Ponds -- South Dakota

Description

Includes bibliographical references (page 49-56)

Format

application/pdf

Number of Pages

79

Publisher

South Dakota State University

Rights

Copyright © 1990. David C. Simon. All rights reserved.

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