Schmidt, Ernst Johannes
SCHMIDT, ERNST JOHANNES
(b. Copenhagen, Denmark, 2 January 1877; d. Copenhagen, 21 February 1933)
Schmidt was the son of Ernst Schmidt, an estate inspector, and Camilla Ellen Sophie Johanne Kjeldahl. His father died when he was seven. Schmidt eventually entered the University of Copenhagen to study botany and in 1898 received the M.Sc. and in 1903 the Ph.D. for a paper on the prop roots of the mangrove. From 1899 to 1909 he was attached to the Botanical Institute of the university, and from 1910 he served as director of the Carlsberg Physiological Laboratory in Copenhagen. Schmidt published numerous botanical papers, particularly on tropical faunas and marine plants; and with F. Weis he wrote a textbook on bacteria.
From 1899 Schmidt was a member of the Danish Commission for the Investigation of the Sea. He went on several marine biological expeditions in the North Atlantic, and his fame rests chiefly on his research there. Schmidt’s interest soon turned to the larval development of fishes, and his first paper on this subject was published in 1904. In the same year he investigated eel larvae and was led into the study of the breeding of eels.
At that time the life cycle of eels was a complete mystery. The larvae until only recently had been described as a separate species; and the breeding grounds were unknown. From his research in the North Atlantic and in the Mediterranean (1908–1910). Schmidt hypothesized that the European eel has a common breeding ground in the Atlantic and that it belongs to a single population. To prove this theory. Schmidt led an expedition to the North Atlantic from 1920 to 1922. By tracing the area where the youngest larvae were found, he eventually located the breeding grounds in the Sargasso Sea. He was able to show that adult eels from all of western Europe and the Mediterranean migrate to this place and die after spawning. The larvae then migrate to their parents’ adult habitats. (He showed also that American eels have a similar pattern and a nearby breeding ground.) This peculiar pattern had profound implications not only in biology but also in the discussion of continental drift.
To extend his theory to all eels, Schmidt received a grant from the Carlsberg Foundation to lead an expedition around the world (1928–1930). During this time, he collected material on other species of fishes as well, especially material on other species of fishes as well, especially deepwater fishes.
Schmidt also studied the eel-like Zoarces viviparus. He showed that this species breeds locally and identified differences between the various populations. Later the extended these observations to other species and made a number of important studies of environmental effects on the size and shape of many populations. Schmidt’s biometric findings contributed to the concept of the interbreeding populations as a fundamental unit. Since most of this research was done on economically important species of fishes, his work was also of great value to fisheries.
Schmidt’s research was highly appreciated during his lifetime, and he received many academic and public honors. He also took an active role in several international organizations concerned with the sea, especially the International Permanent Council for the Study of the Sea, which had its seat in Copenhagen.
In 1903 Schmidt married Ingeborg Kühle, daughter of the director of the Old Carlsberg Breweries. Their home was both a social and scientific center.
I. Original Works. A complete list of Schmidt’s scientific publications is in Regan (see below). His major works are Bakterierne. Naturhistorisk Grundlag for det buktereologiske Studium (Copenhagen, 1899–1901), written with F. Weis, German ed., M. Porsild, trans. (Jena, 1902); “Danish Researches in the Atlantic and Mediterranean on the Life-History of the Fresh-Water Eel (Anguilla vulgaris),” in Internationale Revue der gesamten Hydrobiologie u Hydrographie, 5 (1912), 317–342; and “The Breeding Places of the Eel,” in Philosophical Transactions of the Royal Society, 205 (1922), 179–208.
II. Secondary Literature. The best biography is C. Tate Regan, “Johannes Schmidt,” in Journal du Conseil, 8 (1933), 145–160, with complete bibliography.