Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2002
Publication Date: N/A
Interpretive Summary: The goal of this research was to examine five distinct strains of rainbow trout for differences in growth at two distinct feed levels, immune response to viral immunization, and relative genetic makeup. The results of this study illustrate differences in rainbow trout growth performance associated with feeding level. Feeding to apparent satiation allows the growth potential of the fish to be realized, regardless if appetite contributes to growth potential in a trout strain. Feeding to a fixed level allows potential differences in trout strain performance associated with metabolic efficiency to be determined. In this study, both appetite and metabolic efficiency appeared to contribute to differences among rainbow trout strains in growth performance indices. These differences were found to correlate with level of genetic diversity seen within a strain, such that increased levels of genetic diversity let to a decrease in positive growth attributes. A wide range in the immune response was seen in different strains, and this did not appear to correlate with genetic diversity. This information is important to commercial aquaculture operators and wildlife resource managers because of the impact it has on their choice of fish stocks to be raised in their facilities.
Technical Abstract: The domestication of rainbow trout, Oncorhynchus mykiss, has led to the development of distinguishable isolated populations. In this study five different strains of rainbow trout, two from Idaho, two from Washington and one from Oregon, U.S.A. were examined for variability in growth, immunological response, and genetic diversity. Growth rates for these different strains were monitored and compared for 28 weeks with the animals fed at two rates. Feed conversion ratios (FCR) and specific growth rates (SGR) for the entire period were calculated for each of the strains. The different strains were also evaluated immunologically with infectious hematopoietic necrosis virus (IHNV) and their post- immunization antibody neutralization titers were monitored for a period of 12 weeks. Genetic variability between the strains was examined by extracting DNA from fin clips from a representational sample of the population of each strain. A total of 9 microsatellites with an average of ~10 alleles were evaluated for each strain. The results indicated that the fastest growing strains grew to a set weight of 350 grams more rapidly regardless of whether they were being fed at a fixed level or fed to satiation. These faster growing strains also exhibited a lower FCR and a higher SGR values. The IHNV neutralization titers for the strains varied considerably with one high humoral response group and one low humoral response group. The remaining three strains clustered approximately midway between the other two. Genetically, the strains exhibited a pattern of wide divergence, with only 9 common alleles out of 89 total different alleles between the 5 strains. As expected, commercial aquaculture strains reared locally were closely related.