Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Wildlife and Fisheries Science


Inbreeding in rainbow trout (Salmo gairdneri) was evaluated in relation to an altered environment (upper lethal temperature 29 C), at four levels of inbreeding. At each level of inbreeding mean time to death for inbred, female-outbred half-sib, male-outbred half-sib and outbred families were evaluated. In all cases inbreds were less resistant to lethal temperature than were respective outbred families. Analysis of variance 9Snedecor’s F) and multiple range analysis (Tukey’s “w” procedure) provided inference limitations. Inbred fish were 82% less resistant to lethal temperature as comared to the respective outbred family at 50% inbreeding and 19% less resistant at 25% inbreeding. How inbreeding practices influence stocks of rainbow trout are summarized below: A. Domestic stocks of rainbow trout are inbred to an unknown and varying degree. B. Inbreeding has been common in domestic fish stock for over 100 years in the United States. C. Stocking domestic fish in natural waters has destroyed most genetically unique populations probably by genetic “dilution”. D. Millions of hatchery fish have been broadcasted internationally with unknown consequences in regard to the genetic structure of the original wild populations. E. Inbred groups can show increased phenotypic variation when compared to their outbred countergroups for some traits. F. Highly inbred fish may suffer reduced genetic variability lowering tolerance to environmental rates.

Library of Congress Subject Headings

Rainbow trout
Temperature -- Physiological effect
Fishes -- Breeding


Includes bibliographical references (pages 29-34)



Number of Pages



South Dakota State University


No Copyright - Non-Commercial Use Only