Rapp. P.-v. Réun. Cons. int. Explor. Mer, 191: 339-344. 1989 Johan Hjort - founder of modern Norwegian fishery research and pioneer in recruitment thinking P. Solemdal and M. Sinclair Solemdal, P., and Sinclair, M. 1989. Johan Hjort - founder of modern Norwegian fishery research and pioneer in recruitment thinking. - Rapp. P.-v. Réun. Cons. int. Explor. Mer, 191: 339-344. A description of some major scientific controversies prior to 1914 that influenced the development of Hjort's thinking is presented. Particular attention is given to the difficulties encountered with the migration theory (which explained interannual fluctuations in fisheries landings in the North Atlantic) and the debate on local populations, overfishing, and the role of hatcheries in increasing yields from marine fisheries. The steps leading to his classic 1914 paper are summarized and highlights of the 1914 paper are discussed. It is concluded that Hjort’s work between 1893 and 1917 led to a shift in emphasis from adult migration to early life history processes in the study of interannual fluctuations in yield. P. Solemdal: Institute o f Marine Fisheries Research, P.O. Box 1870, N-5024 Bergen, Norway. M. Sinclair: Department o f Fisheries and Oceans, Halifax Fisheries Research Laboratory, Halifax, Nova Scotia B3J 257, Canada. Introduction Problems in the 1890s The great fluctuations in the fisheries of northern The major scientific problem facing marine biologists Europe at the end of the last century had enormous and oceanographers in the latter half of the 19th century influence on the economy. It was at this time that was an explanation of the interannual fluctuations in the question of overfishing was formulated. The ruling landings from diverse traditional fishing-grounds in concept of those days was that fluctuations in fish stocks northern European waters. The explanation of that time were exclusively the result of varying availability and was the “migration theory” (see Heincke, 1898). The migrations, not of changes in production. The four theory was developed in the 18th century during a factors that overturned this concept were the following: time when the typological species concept was accepted without question. Overall abundance of exploited 1. The discovery of separate self-sustaining populations resources was considered to be essentially unlimited and within the geographic area of the species (Heincke, renewal from year to year relatively constant. In modem 1898). terminology, fluctuations in landings at particular geo­ 2. The discovery of a method for aging fish by otoliths graphical locations within the distributional range of the and scales, which made possible both growth and species were interpreted under the migration theory year-class analysis. to be exclusively due to annual availability changes. 3. Hjort’s idea for a quasi-age census of fish stocks from According to the theory, change in adult migration his work on accident insurance for fishermen, which behaviour in relation to physical oceanographic varia­ he developed into a system for representative sam­ bility generated fluctuations in landings. pling of the different stocks. Hjort at the beginning addressed the problem of the 4. The role of the cod hatchery studies on Hjort’s think­ great fluctuations in yield from the perspectives of this ing about the problem of fluctuations. theory (Hjort, 1895). A number of scientific debates The paper includes the main events and investigations undermined his support of the theory and gradually that led to “Fluctuations in the great fisheries of north­ changed his thinking. ern Europe” (Hjort, 1914). 339 The cod hatchery in Flødevigen bation, and the sudden dramatic mortality of the hatch­ ery larvae when the yolk sac was exhausted. The pioneering work of G. O. Sars (1879) on “winter Dannevig defended the sea-hatching in a series of cod” in Lofoten during the years 1864-1869 revealed pamphlets (Dannevig, 1899, 1903, 1906). He criticized several basic aspects, (for instance, the description of the migration hypothesis in several ways, referring to the pelagic egg). Having a so-called applied science the limited migrations of cod as demonstrated by Sars background, Sars already in 1865 felt pressed to bring (1879), and the improbability of cod changing colour forward the idea of hatching cod eggs to improve cod during its life cycle: fisheries. It is therefore unnecessary to alter either Colour or Form, In 1852 a government report based on hearsay evi­ to have either Impression or Insight, in short no complex dence concluded that local fisheries along the Theories to explain the Relationships. And how should it be otherwise? The Cod has but one Occupation, namely Norwegian coast were declining. In 1884, the cod hatch­ to eat, and when it has Food enough where it is, why should ery in Flødevigen close to the town of Arendal began it then partake of these all-encompassing Migrations? releasing yolk sac larvae of cod into the sea. The hatch­ It is shown here, as so often elsewhere, that the actual ery was a private enterprise, based on the very sound Relationships within Nature’s great House are not as economic conditions of this town (Dannevig, 1973; complicated as we Men are initially inclined to believe. There are but the supreme Masters who with the simplest Solemdal et al., 1984). The pioneer was the captain of Means are able to bring forth the greatest Results. (Dan­ a sailing vessel and an experienced fisherman, G. M. nevig, 1899, p. 43.) Dannevig (Fig. 1). He was convinced that the release Dannevig had several reasons for criticizing the of yolk sac larvae would increase the local cod stock migration hypothesis; it did not include either over­ for the benefit of the fishermen. No investigations for fishing or the existence of local cod stocks, both pre­ testing the effects of this activity were carried out; only suppositions for hatching operations. It is evident that in hearsay evidence existed. When Johan Hjort became those early days of Norwegian fishery research Captain leader of fisheries research in 1893, demands for more Dannevig’s practical experience, enthusiasm, and pol­ scientific methods for testing the hatching programme emical force were important to Hjort and Dahl. were put forward. Due to decreasing landings in the coastal waters of In the 1890s, only preliminary investigations were Scotland, a similar hatchery was built at Dunbar and carried out, indicating that eggs and larvae were swept directed by Captain Dannevig’s son Harald (Dannevig, out of the fjords and returned later as fry (Hjort and 1896). Discussing the effects of the hatchery work, Dahl, 1899, 1900). Though negative to the effects of Cunningham (1896) states: releasing yolk sac larvae to improve cod fisheries, Hjort, It is generally admitted that the benefit effected by merely and especially Dahl, one of his students, became fam­ hatching the eggs and then consigning larvae to the sea, iliar with the early life history of the cod: its enormous is not likely to be so great as which might be secured by fecundity, the relatively small mortality during egg incu­ protecting the young fish in their early and delicate stage. Figure 1. Captain Dannevig inspecting the catch of a beach seine haul (Flødevigen Biological Station archives). 340 In sum, both the Norwegian and Scottish hatchery (1914). But he did not give up his "migration” think­ experiments focused attention on the high levels of ing completely! mortality that occur naturally during the early life his­ 3. Dahl’s investigation on the effect of sea-hatching. tory stages of marine commercial fish species, and on the importance of resolving the debate on the existence During 1903-1905, systematic investigations on sea- of local populations. It is interpreted here that this shift hatching were carried out in some small fjords along in emphasis from availability fluctuations during the the Skagerrak coast. In 1903 no larvae were released, adult stage to focusing on early life history stages of but during the subsequent two years a large number of geographically restricted populations was an important yolk sac cod larvae were released into the fjords. The precursor to the paradigm shift of Hjort (1914). plan included beach seine sampling both in July and September. This was Hjort’s idea to verify the previous results from the 1890s in the Trondheimsfjord and the The golden age in Norwegian marine Kristianiafjord, where no bottom stages were found in research, 1900-1914 July, supporting the theory that no local populations of The publication of Heincke’s "Naturgeschichte des Her­ cod existed (Hjort and Dahl, 1899, 1900). The beach ings" in 1898 introduced a revolution in fisheries seine programme was originally put forward by Dan­ research (Sinclair and Solemdal, 1988). Population nevig in 1893. structure was a necessary concept in the understanding The relationship between Captain Dannevig and of the fluctuations of fisheries. However, the migration Hjort was still negative: Hjort did not believe in cod- hypothesis still prevailed, implying variable long dis­ hatching and he was also very little concerned about tance migrations and a constant production from year the “daily fishery” (i.e. nearshore fisheries from small to year (Sinclair, 1988). boats), while Dannevig was an advocate for coastal In 1902, the ICES scientific committees met in Edin­ fishermen with a very negative attitude to scientists in burgh for the first time, Committee A, “Fish general. Given this background, Hjort did not rely on Migration”, convened by Hjort, and Committee B, Dannevig’s abilities to perform the investigations, and “Overfishing”, convened by Garstang. Both Com­ Dahl was appointed to control the catches from the mittees became involved in the problem of year-class beach seine hauls. During this joint investigation, 252 variations, Committee A in its work to document the beach seine hauls were carried out in July and 4931 migration hypothesis, Committee B as a spin-off from juvenile cod were collected.