Fischer was the son of a Munich schoolmaster, also named Johann Baptist, and his wife Cäcilie Haimerl. His younger brother was Sebastian Fischer, who also became a physician and naturalist spending part of his career in Russia and then Egypt. J. B. Fisher was the assistant of the botanist
Carl Ludwig Blume in the former national herbarium of
Brussels. In 1826, he joined an expedition to
Java, then a possession of the
Dutch East Indies, and participated with Blume in writing the description of the species collected. During the Belgian revolution of September 1830, he helped
Philipp Franz von Siebold transferring herbarium specimens from Brussels to Leiden in the Netherlands. Johann Baptist Fischer also devoted himself to the study of mammals, and he published in 1830 his
Synopsis Mammalium. He died at a young age from septic infection. == Taxonomic descriptions ==