Herring periods of Bohuslän: a cross-sectoral approach

Herring periods have occurred in Bohuslän, on the west coast of Sweden, at least since the 16th century, probably even earlier. The first scientific description was given by Axel V Ljungman, who arranged the occurrence of herring into periods which seemed to be related to sun-spot activities. The reappearance of herring by the end of the 1870s — the last herring period — inspired the oceanographers Otto Pettersson and Gustaf Ekman to ask for international cooperation in marine research, which eventually led to the Stockholm Conference in 1899. Pettersson and Ekman thought that movements of the upper water layers were related to the appearance of herring. Later, Pettersson was more in favour of large tidal forces as the cause for herring periods. K. A. Andersson had difficulty in finding a direct connection between oceanography and herring occurrence and emphasized that the herring stock had to be very large before any herring period could occur. For the successful identification of the type of herring which caused the period starting in the 18th century, Hans Höglund conducted excavations of herring waste deposits buried on land as a result of environmental protests of that time, thus adding archaeology to the efforts. Studies of climate and variations in herring populations by Jürgen Alheit and Eberhard Hagen pointed to the North Atlantic Oscillation (NAO) as the ultimate environmental driving force necessary for a herring period. A relationship between herring periods of Bohuslän and the medieval herring fishery farther south off Scania has not been found. An accumulated stock of large year classes of herring seeking shelter during the winter months in the archipelago of Bohuslän is the necessary precondition for a herring period, especially when there are low winter severity/mildness indices.

Article from Marine Science Symposia Vol. 215 - 100 years of science under ICES. To access the remaining articles please click on the keyword "MSS Vol. 215".