02932nas a2200205   4500008004100000050007700041245007300118210006900191250001100260260005100271300001000322520219500332653001602527653001302543653003902556653001402595653001102609100001602620856009002636       1973                        eng d  aOSU Libraries: Valley LD4330 1973D .L3, Guin Lannan, Digital Open Access00aGenetics of the Pacific Oyster; Biological and Economic Implications0 aGenetics of the Pacific Oyster Biological and Economic Implicati  aPh. D.  aCorvallis, Or.bOregon State University,c1973  a104 p3 a     Variance among individuals within populations are influenced by environmental and genetic factors. Utilizing quantitative genetic theory, environmental and genetic components of variance have been compartmented for a variety of quantitative characters of the Pacific oyster, <u>Crassostrea gigas</u>.       A significant genetic component of variance in a quantitative attribute related to reproductive fitness implies that selection is being effected upon the system. In the present investigation, the variance of larval survival has been subjected to a genetic evaluation. A statistically significant genetic component of variance has been observed. It is concluded that under the conditions observed, genetic selection is inherent in hatchery operations directed toward the management of this species. The genetic  implications of these selective practices are discussed in the text of this thesis. It is suggested that this method for the genetic evaluation of hatchery practices is applicableto other aquatic animals which are propagated in hatcheries.      The genetic and environmental components of variance have been estimated for several other economically significant attributes of <u>C. gigas</u>. In every case, a significant genetic component of vanance was observed. Further compartmenting of the genetic variance into additive and non-additive genetic components revealed that a large non-additive component was present in every case observed. This is interpreted as being a consequence of introducing a wild animal into a selective, quasi-domestic culture  situation. It is considered likely that after several generations of hatchery culture, selection plateaus will be attained and additive genetic variance will increase relative to other variance components.      Based upon these observations, a method for selective breeding of oysters has been proposed. It is suggested that progeny testing is the breeding method best suited for the early stages of selective breeding with oysters and probably for aquaculture in general. Preliminary tests of this method suggest that significant economic gains may be realized through selective breeding of the Pacific oyster.10aaquaculture10agenetics10aPacific oyster = Crassostrea gigas10ashellfish10atheses1 aLannan, Jr.  uhttps://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/q811kn84d