鱼汁 has two senses: (1) the fermented condiment we call fish sauce in English — though mainland Chinese menus more commonly say
鱼露 yúlù for this, and
鱼汁 stays more colloquial; (2) the natural juices released while steaming or braising fish. Xinhua defines it as
鱼汤 (fish-based broth with seasoning).