Food for Thought The graceful sigmoid: Johan Hjort's contribution to the theory of rational fishing

Johan Hjort is widely known and honoured for his immense contributions to oceanography and fisheries ecology. He is less well known for his seminal role in promoting the application of science to whaling and the conservation of the great whales. I hope to correct the balance. The first formal international agreement on the conduct of whaling, including a number of regulations intended to limit or control commercial whaling, was negotiated in 1931 under the auspices of the League of Nations in accordance with an initiative launched in 1926 by the International Council for the Exploration of the Sea (ICES). The first important move in August 1929 under the ICES initiative was the appointment of an International Statistics Committee (ISC) chaired by Gunnar Jahn, Director of the Norwegian Statistical Bureau, with Sigurd Risting, Secretary of the Association of Whaling Companies (AWC), and Johan Hjort as members. Risting was effectively the founder of the Bureau of International Whaling Statistics. He had been collecting whaling statistics on his own since the end of the 19th century, completing them, as far as was possible, back to the beginning of “modern whaling” in 1868 (i.e. using steam catcher boats, bow-mounted cannons, and a harpoon with a grenade head). In addition, as Secretary of the AWC, he had as early as 1919 asked the Directors of the whaling companies to ensure that the lengths of all whales killed in the Antarctic were measured, including the sizes of foetuses in the pregnant females. Hjort served on the ISC until 1939 when he resigned. During the 1930s, Hjort was the scientific brain behind the construction of the best international database ever assembled on whale fisheries. Interest in whaling was not a side line. The catching and processing of the largest baleen whales—blue, fin, humpback, and sei—was by far the biggest Norwegian fishery in terms of sheer quantity and economical importance of all Norwegian fisheries during the inter-war years. This fact has been obscure simply because whale catches were always recorded as numbers, not weights, and the significance of the records of quantities and prices of products from the whales was not always noticed. The whaling database was remarkable, especially because it recorded not only catches but the whaling effort, biological information about whales, the details of the whaling fleets, the quantities and values of products and some other economic data, particularly about whale oil. The information was collected by national inspectors on whaling factory ships. Thus, by the beginning of World War II, Hjort and his colleagues had a fairly good idea of the states of the populations of the whales that migrated to and from their Antarctic feeding grounds, which were targeted by the whaling industry. They based their assessments on changes in relative abundance (derived from catch-per-unit-effort data), size compositions, proportions of mature and immature animals, sex ratios, longitudinal and limited latitudinal movements within the Southern Ocean, the timing of migrations and growth of the whales during the feeding season.