Evaluating a new population of Kumamoto oysters (Crassostrea sikamea) for breeding on the U.S. Pacific Coast

Authors: LANGDON, CHRIS - Oregon State University; DE MELO, CLAUDIO - University Of Santa Catarina; DIVILOV, KONSTANTIN - Oregon State University; SCHOOLFIELD, BLAINE - Oregon State University; MERZ, NOAH - Oregon State University; Thompson, Neil

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2024
Publication Date: 12/27/2024
Citation: Langdon, C., de Melo, C.M., Divilov, K., Schoolfield, B., Merz, N., Thompson, N. 2024. Evaluating a new population of Kumamoto oysters (Crassostrea sikamea) for breeding on the U.S. Pacific Coast. Aquaculture. 598. Article 742031. https://doi.org/10.1016/j.aquaculture.2024.742031.
DOI: https://doi.org/10.1016/j.aquaculture.2024.742031

Interpretive Summary: Kumamoto oyster (Crassostrea sikamea) is a commercially important species for the United States Pacific coast shellfish aquaculture industry. Historically, few sources of Kumamoto oysters have been available, but a new population, sourced from the native range in Japan was imported by the Molluscan Broodstock Program at Oregon State University in 2006. This study describes the importation, propagation and evaluation of the new Kumamoto oyster population and its potential for improvement via genetic selection. The newly sourced population was compared with an existing commercial population from U.S. commercial hatcheries in 2 generations. Using 5 generations of data, multiple traits were evaluated, including survival, growth and shell shape metrics. Heritability estimates varied among generations, but were moderate to high for most traits indicating that genetic selection could influence mean trait values. During generations 2 and 3, the newly sourced population had statistically smaller body sizes, but similar survival compared to the existing commercial population. The fifth generation of the newly sourced population was evaluated at multiple sites, including a sub-tidal coastal site in Oregon and an inter-tidal Puget Sound (Washington) site. Strong site effects were present, but no significant re-ranking of family performance occurred, suggesting no Genotype-by-Environment interaction. This indicates that selection for any single trait is likely to show improvement across multiple waterbodies, which is an important parameter to understand for breeding program efforts. Overall, the importation of the new population was highly successful, and has resulted in the establishment of a more diverse Kumamoto oyster population that is available to commercial hatcheries for spawning and aquaculture production by the U.S. Pacific coast shellfish industry.

Technical Abstract: We describe the introduction, evaluation and integration of Kumamoto oysters (Crassostrea sikamea) collected from the Ariake Sea, Japan in 2006, to create a new Kumamoto breeding population for the US Pacific Coast. The collection and species verification of G0 Kumamoto oysters from the Ariake Sea, Japan were described by Camara et al. (2008). In this study, we describe the addition of progeny of this G0 broodstock to create a new Kumamoto oyster breeding population for the US Pacific Coast. The G1 generation and early life stages of the G2 generation were reared under quarantine conditions with frequent disease testing. Families of G2 spat with no detectable diseases, were released from quarantine and planted at a sub-tidal farm test site in Yaquina Bay, Oregon. Phenotypic characteristics of G2 and G3 cohorts were compared with those of Kumamoto oysters from an established Pacific Coast commercial stock, as well as with outcrosses produced by crossing Japanese and Pacific Coast Kumamoto broodstocks. Yields, survival, individual average weights, individual weights, as well as shell width, shell depth and shell shape index [SSI; shell depth/(width+length)] of these three populations of Kumamoto oysters were not significantly different, except for significantly greater individual weights and shell lengths of Pacific Coast compared with Japanese Kumamoto families. Overall, many of the desirable harvest traits of the Japanese Kumamoto stock, except survival and SSI, showed high heritabilities and positive medium-to-high genetic correlations, suggesting that gains could be achieved via selection. No hybridization with Pacific oyster (Crassostrea gigas) was identified in the broodstock used to create the G4 and G5 generations. Based on these results, the new Japanese broodstock was crossed with an established US Pacific Coast stock to create a new breeding population for the Pacific coast shellfish industry.