This restaurant is famous for its fresh seafood, especially various types of shellfish.

shellfish 是复合名词，由 shell（壳）和 fish（鱼）组成。shell 指"外壳、硬壳"，fish 指"鱼类"。shellfish 字面意思是"带壳的鱼"，实际指"贝类海鲜"，包括牡蛎、蛤蜊、扇贝等带壳的海洋生物。