Charles Marcus Breder Jr.

Charles Marcus Breder Jr. (June 25, 1897 – October 28, 1983) was an American ichthyologist, aquarium manager and museum curator.

Breder was born in Jersey City, New Jersey and grew up in Newark, New Jersey. He did not attend university but managed to be appointed as a scientific assistant in the U. S. Bureau of Fisheries in 1919, Breder later said that all of his knowledge of biology and ichthyology had been gained at the Newark Public Library. Breder's only university level qualification was an honorary doctorate from the University of Newark.

After two years at the Fisheries Bureau he left for a position as an aquarist at the New York Aquarium, where he remained despite conflict over the aquarium's role in research with its director, Charles Haskins Townsend and while there heparticiupated in field expeditions to Panama, Florida, the Bahamas, Mexico, the Sargasso Sea and the Caribbean. It was during this period that Breder devised a technique for keeping the seawater in the aquarium at the correct pH for marine fish at sites with no access-to fresh seawater, this involved additions of sodium bicarbonate to the water at set periods. Townsend retired in 1937 and Breder was appointed as the aquarium's acting director, being confirmed as the director in 1940. Especially later in his career Breder avoided participating in Scientific Societies, although he did serve as president of the American Society of Ichthyologists and Herpetologists in 1932.