More than ten years ago, Tsai's research subject was edible aquatic species. He worked on making fish and shellfish such as Taiwanese abalone grow faster and yield higher-quality flesh, and on giving shrimp better disease resistance. Although his initial development efforts were successful, he did not pursue this research direction further, the main reason being the difficulty of manipulating transgenic fish.
十多年前，蔡懷楨研究的對象是食用水產，致力於讓魚和九孔等貝類長得比較快、肉質佳，讓蝦子有抵抗疾病的能力等，雖然已初步開發成功，但卻沒有進一步推廣、發展，關鍵便在於基因轉殖魚不容易控制。