Johan Hjort

Johan Hjort ForMemRS (18 February 1869 – 7 October 1948) was a Norwegian fisheries scientist, marine zoologist, and oceanographer. He was among the most prominent and influential marine zoologists of his time.

Johan Hjort was the first child of Johan S. A. Hjort, a professor of ophthalmology, and Elisabeth Falsen, of the Falsen family. Among his siblings was the engineer Alf Hjort, who became a leader of subwater tunnel constructions in New York City. Johan Hjort had wanted to become a zoologist since his early schooldays, but to please his father he took initial courses in medicine, before following Fridtjof Nansen's advice and his own wish, leaving for the University of Munich to study zoology with Richard Hertwig. He then worked at the Stazione Zoologica in Naples on an embryological problem, which led to his doctorate in Munich at the age of 23 in 1892. He returned to Norway to become curator of the University Zoological Museum, where he developed more modern courses for students, and in 1894 he succeeded G. O. Sars as Research Fellow in Fisheries. After a year at University of Jena he was in 1897 appointed the directorship of the University Biological Station in Drøbak.

Hjort became the director at the Norwegian Institute of Marine Research in Bergen, from 1900 to 1916. His early influences abroad kept him involved in international research work, and he was among the founding fathers of International Council for the Exploration of the Sea (ICES) in 1902. He was the Norwegian delegate at ICES from 1902 to 1938, when he was elected President, a position he held to his death in 1948.

In 1909, Sir John Murray wrote to the Norwegian government that if they would lend the Michael Sars vessel to him for a four-month research cruise, under Hjort's scientific command, then Murray would pay all expenses. After a winter of preparation, this resulted in what was by that time the most ambitious oceanographic research cruise ever. The 1912 Murray and Hjort book The Depths of the Ocean quickly became a classic for marine naturalists and oceanographers.

For several years, Hjort had been interested in the statistical nature and causes of the large fluctuations of fish populations. He was the first to apply actuarial statistical methods to study these phenomena, aided also by measurement techniques that made it possible to estimate the age of sampled fish. Hjort's studies culminated in the 1914 article Fluctuations in the Great Fisheries of Northern Europe, which was a pivotal work in the development of fisheries science.

These studies made him interested in population dynamics more generally, the challenge of understanding the growth of populations of different organisms, ranging from cultures of yeast at one extreme to man, whales and fish at the other. He considered implications of such studies important also for human society, influenced in such views by Malthus, Darwin and others. He was early on concerned with effects of over-fishing, with the declining whale populations in the Antarctic an early warning, and worked on methods for determining the optimum catch that would secure sustainable populations.

Hjort was a versatile individual who could also apply his broadly based theoretical knowledge in strikingly practical ways. In 1924 he invented novel industrial mechanical machinery for extraction of whale oil from blubber. He is also credited with being the "practical inventor of shrimp fishery", on both sides of the Atlantic. The shrimp, in particular the deep-water shrimp Pandalus borealis, were known species, but were considered rare and not worth looking for. Around 1898, Hjort adapted earlier designs of deep-sea trawls on the soft bottoms of the deep Norwegian fjords and soon discovered enormous stocks of Pandalus borealis. This at first did not impress the fishermen. As H. G. Maurice, the 1920–1938 President of ICES, recalls, "Hjort wasted no time in argument. He went prawn fishing, returned to harbour with a spectacular catch and dumped it on the quay. That was enough. With that practical demonstration he laid the foundation of an exceedingly profitable fishery and a flourishing export trade". Many years later, when travelling to Harvard in 1936 to collect an honorary degree, he predicted that the deep-sea shrimp would be found off the New England coast, since the ecological conditions were similar to those of the soft-bottomed Norwegian fjords. Taking time off to pursue his hypotheses, he was given command of the research ship Atlantis, and found vast amounts of shrimp exactly where he predicted they would be; this led to the formation of a shrimp fishery industry on the US side.

During the First World War, Hjort became engaged to some extent in politics and specifically foreign relations with both Germany and Britain. Hjort was asked to take part in negotiations between Norway and England to reach agreement on fish-purchase, and he did so, on the assumption that the agreement would be made public. Norway's foreign minister Nils Claus Ihlen, who was afraid of German reprisals, demanded however that it should be kept secret. In protest, Hjort resigned, both from the negotiations and also as Director of Fisheries, and left Norway for some years. After spending time in Denmark and at the University of Cambridge, he was given a professorship in Oslo from 1921.