(b. Christiania [now Oslo], Norway, 18 February 1869; d. Oslo, 7 October 1948)
Hjort was the son of Johan Storm Aubert Hjort, professor of ophthalmology at the University of Oslo, and Johanne Elisabeth Falsen. After completing preclinical medicine at Oslo, he shifted to zoology at Munich under Richard Hertwig and later went to the Zoological Station, Naples, where he worked on budding of the Ascidian genus Botryllus.
He pursued an academic life as lecturer in zoology at Olso until 1900, although his future as a practical fisheries biologist was presaged by his discovery in 1897 of stocks of the deep-sea prawn Pandalus borealis, a species with commercial potential in the Norwegian fjords.
He was founder and first director (1900–1916) of the Norwegian governmental fisheries (Bergen) and as such became highly regarded in fisheries affairs, not alone from the purely scientific and the applied aspects as related to the industry but also with respect to the fishermen’s welfare. During this period Hjort made substantial contributions to marine knowledge with his “Fluctuations in the Great Fisheries of Northern Europe” (Rapport et procès-verbaux, 20 ). He mapped the distribution and frequency of the pelagic eggs of the various cods as delimited by the temperature and salinity characteristics of North Atlantic water masses, aided in these findings by D. Damas; he was also responsible for locating spawning areas and hitherto neglected fishing banks. Small wonder that he was for forty-six years delegate from Norway to the Conseil Permanent International pour l’Exploration de la Mer, a vice-president for the last ten years of his life.
About 1900 the techniques of age determination in fishes by scale analysis were becoming established. With this tool at hand, Hjort, with Einar Lea, was able to delineate the age structure of the Norwegian herring population over several decades and to demonstrate the phenomenon of year-class dominance, that is, the successful survival of the young in nature, in any one year, in such numbers as to dominate the population as juveniles and adults over a succession of seasons. Hjort traced the spectacular 1904 year class of herring from 1907, when it entered the commercial fishery, to age fifteen in 1919; this age group was predominant in the catch over much of this span, particularly so in 1910 (77.3 percent), and even in 1919 it shared dominance with the good year class born in 1913.
Hjort’s consuming interests led him in diverse directions: the sigmoid curve, yeasts, the “optimum catch,” whales, philosophy, and politics and diplomacy. His role in international fishery matters included negotiations with Great Britain about the limits of territorial waters off Norwegian coasts, as well as dealings concerned with abatement of over- fishing of whale stocks in the Antarctic (Hvalradets skrifter, nos. 3, 7, 8, 9, 12, 14, 17, and 18 [1932–1938]).
In the field o marine ecology he is perhaps best known for the classic volume, coauthored with Sir John Murray, The Depths of the Ocean, the result of an expedition on the Norwegian research vessel Michale Sars in the North Atlantic (1910).
His admiration for the English and their culture, as well as the esteem in which he was held in scientific circles abroad, was reflected by his election to the Royal Societies of London and Edinburgh, the Geographical, Zoological, and Linnean Societies of London, as well as the Royal Irish Academy, the Paris Academie des Sciences, and the American Philosophical Society. He was professor of marine biology at Oslo from 1921 until reaching the age of retirement in 1939.
I. Original Works. Among Hjort’s writings are The Depths of the Ocean (London, 1912), written with John Murray; “Fluctuations in the Year Classes of Important Food Fishes,” in Journal du Conseil, 1 , no.1 (1926), 5–38; “Essays on Population,” in Hualradets skrifter, no.7 (1933), pp. 5–152, with 6 plates; The Restrictive Law of Population, Huxley Memorial Lectures, Imperial College of Science and Technology (London, 1934); and The Human Value of Biology (Cambridge, Mass., 1938).
II. Secondary Literature. Obituaries are “Prof. Johan Hjort, a Marine Biologist,” in New York Times (9 Oct. 1948), p. 19; “Prof. Johan Hjort,” in The Times (London) (12 Oct. 1948), p. 7; H. G. Maurice, “Prof. Johan Hjort, For. Mem. R.S.,” in Nature, 162 , no. 4124 (1948), 764–766; K. A. Andersson, “Johan Hjort, 1869–1948,” in Journal du Conseil, 16 , no. 1 (1949), 3–8; A. C. Hardy, :Johan Hjort,” in Proceedings of the Royal Society (obit. notices), 7 (1950), 167; and Johan T. Rudd, “Minnetale over Professor Dr. Johan Hjort,” in Årbok 1949. Norske videnskapsakademi i Oslo (Oslo, 1950), pp.47–69.