Charles Henry Gilbert was a pioneer ichthyologist and fishery biologist of particular significance to natural history of the western United States. He collected and studied fishes from Central America north to Alaska and described many new species. Later he became an expert on Pacific salmon and was a noted conservationist of the Pacific Northwest. He is considered by many as the intellectual founder of American fisheries biology. He was one of the 22 "pioneer professors" of Stanford University.

Ichthyology is the branch of zoology devoted to the study of fish, including bony fish (Osteichthyes), cartilaginous fish (Chondrichthyes), and jawless fish (Agnatha). According to FishBase, 33,400 species of fish had been described as of October 2016, with approximately 250 new species described each year.