Trial production of settlement-stage larvae of the iwagaki oyster Crassostrea nippona using a 100 kl tank in a semi-outdoor environment
2014
Sasaki, T. (Shimane Prefectural Fisheries Technology Center, Oki, Shimane (Japan). General Coordination Division) | Tokiwa, S.
Production of settlement-stage larvae of iwagaki oyster Crassostrea nippona was performed using a large tank (100 kl) in a semi-outdoor environment. To simplify rearing procedures, routine bottom cleaning and replacement of sea water were not undertaken for the duration of larval production. Two trial productions were performed and larvae were reared on two or three different microalgal diets. In the first trial, 35 million settlement-stage larvae were produced on a diet of Chaetoceros calcitrans (commercial diet), Isochrysis sp. (T-ISO) and Chaetoceros gracilis, given in that order. In the second trial, 122 million settlement-stage larvae were produced on a diet of Isochrysis sp. (T-ISO) and C. gracilis, given in that order. The survival rates of larvae at the settlement stage in both first and second trials were 63.1 % and 79.5%, respectively. These values were higher than those obtained through conventional production methods using small tanks (1 kl). Since the time allocated to daily larval management procedures (e.g. cleaning etc.) was markedly reduced, and the diet used was produced outdoors comparatively easily, the rearing methods employed in this study are considered to be well suited for large-scale production of iwagaki oyster seeds in the early part of the larval seed production season.
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