Seeking of Oyster Traits for Simple Indices to Evaluate Marketability of Cultchless Single Pacific Oyster, Crassostrea gigas
Young-Ghan Cho, Hye-Mi Lee, Jeong-Hwa Kim, Jong-Seop Shin, Kwang-Sik Choi, Jung-Ha Kang, Hee-Do Jeung
Department of Marine Life Science (BK21 FOUR), Jeju National University, 102 Jejudaehakno, Jeju, 63243, Republic of Korea West Sea Fisheries Research Institute, National Institute of Fisheries Science (NIFS), Incheon, 22383, Republic of Korea Tidal Flat
As demand on live and half-shell oysters increases globally, the appearance of the oyster is becoming one of the important determinants of marketability. In terms of oyster shape, cultchless single oysters have advantages over the conventional cultched oyster, as the shape of a single oyster is intermittently managed during the grow-out period, resulting in round individuals that are consistent in shape and size. Although a growing number of oyster producers in Korea culture cultchless single oysters, there is no consensus on ‘good-looking shape’ and high marketability among oyster producers and consumers. In this study, we applied three known oyster grades (total weight, SL:SH, and SL based) to Pacific oyster groups to assess the feasibility of the grading system. In addition, the mean condition index (CI) of the oysters corresponding to each category in the grade was compared to decide traits that could be applied in oysters produced in Korea. A total of 888 collected oysters includes diploid oysters reared by long-line culture (2-yrs, 113.9 ± 18.5 mm in SL), diploid (1-yr, 79.5 ± 11.7 mm), and triploid (3-yrs, 152.7 ± 22.6 mm) oyster reared individually in hexagonal plastic containers. The results revealed that the Canadian SL/SH-based grade was applicable, as the single oyster groups with the upper grades demonstrated significantly higher CI than those in the lower grades. We also found a positive correlation between SH/SL ratio and CI in the single oyster group, indicating that oysters with the teardrop shape tend to show a higher CI. It was also notable that any of the traits were not correlated with CI in the cultched oyster group. Thus in this study, we suggest SL/SH ratio as a single oyster trait that could be utilized in oyster grading system.
  
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