From Japanese-English FreeDict Dictionary ver. 0.1:
牡蠣 /(en)tʃˈaɪniːz(ja)lˈe̞tə (en)tʃˈaɪniːz(ja)lˈe̞tə/, 牡蛎 /(en)tʃˈaɪniːz(ja)lˈe̞tə (en)tʃˈaɪniːz(ja)lˈe̞tə/, 蠣 /(en)tʃˈaɪniːz(ja)lˈe̞tə/, 硴 /(en)tʃˈaɪniːz(ja)lˈe̞tə/, かき /kˈäki/, (牡蠣) (牡蛎) ぼれい /bo̞ɽˈe̞i/, () カキ /kˈäki/ (noun (common) (futsuumeishi))
Note: word usually written using kana aloneoyster, oyster shell