Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Wildlife and Fisheries Science

First Advisor

Raymond Simon

Second Advisor

Charles G Scalet


The breeding of farm animals to produce superior organisms has been extensively applied to many parts of the world. Much of the research has been concerned with the manip0ulation of muscle protein and fat in muscle tissue for the purpose of catering to human needs (Kielanowski 1972; Dinkel and Busch 1973; Olson et. al. 1976). Though fishes are able to convert food to quality protein more efficiently than most animals, they have been underutilized as a protein source in the United States. Until recently, genetic manipulation through selection to enhance their quality has not been extensively applied (Smith and Rumsey 1976). Because of the increasing need for quality protein in the world, fish rearing, and subsequent character improvement should become a more important part of world protein production. In order for fish production o be efficient, on basic requirement will be the production of an organism that will perform will in a hatchery condition (Gjedrem 1976). Artificial selection for increased growth, survivability, and disease resistance has been investigated in hatchery and wild strains of salmonids (Donaldson and Mensveta 1961; Aulstad et al. 1972; Gjedrem and Aulstad 1974; Kanis et al. 1976; Kincaid et al. 1976; Refstie et al. 1977). The use of wild strains, however, has been minimal due to their limited accessibility and poor performance in artificial rearing conditions (Reisenbichler and McIntyre et al. 1979). The potential to increase or at least maintain genetic variability in hatchery strains may increase their utilization. Regulating the body composition of fish for a specific purpose will become an increasingly important requirement in fish production (Gjedrem 1976). Little is known about the degree of genetic influence (heritability) on body composition of fishes (Simon 1970), though it has been investigated in lab and farm animals (Dinkel and Busch 1973; Notter et al. 1976; Brown et al. 1977). Reinitz et al. (1979) found body composition differences among various strains of rainbow trout (Salmo gairdneri) and Gjedrem (1976) found differences in fillet quality among rainbow trout. Results from both these studies suggest potential for genetic improvement in this fish. Genetic variation is believed to be 50% greater in fishes than in mammals (Ayala 1976). Gjedrem (1976) found coefficients of variation for economically important quality traits such as meat color and carcass score to average 30% in rainbow trout compared to 5-20% for similar characters in farm animals. Therefore increased genetic variability in addition to greater fecundity allow a greater potential for selective breeding among fishes than domestic livestock. Phenotypic and genotypic correlations are important considerations when trying to alter the frequency of a particular trait in a population, for a change in one trait may have pronounced effect on another (Falconer 1972). In selecting for body composition traits and overall quality improvement, it may also be more convenient and efficient not to select directly on the basis of composition analyses and taste testing but indirectly on the sue of some more readily available statistic such as weight. Reinitz et al. (1979) found a significant (p<.01) association between growth and percent protein on a dry weight basis. This suggests the possibility that direct selection for weight could bring about a measurable change in protein on a dry weight basis. My objectives were to estimate heritabilities and phenotypic variances in rainbow trout for the traits: percent moisture, percent protein on a dry and wet weight basis, percent fat on a dry and wet weight basis, percent ash, standard length, weight, and K (condition factor). Another objective was to estimate phenotypic and genotypic correlations involving these traits. A final objective was to evaluate the potential for genetic alteration through direct and indirect selection of the above traits.

Library of Congress Subject Headings

Rainbow trout
Fishes -- Growth
Fishes -- Genetics
Fishes -- composition


Includes bibliographical references (pages 30-34)



Number of Pages



South Dakota State University