Herring periods and cod periods along the Norwegian coast have been known for more than 1000 years. Periods of growth in the fisheries, have formed the basis for settlement, industrialization, economic growth, and wealth. Periods, when the fish disappeared, led to emigration, hunger, and poverty.
Over the years, one has questioned whether good years, or bad years, were accidental, or ruled by higher powers. The fish stock grew during the 1940s. After 1945, a new fishing fleet was built, which had good years in the 1950s and 1960s. In the 1970s, the herring stock and the cod stock disappeared. Questions were then asked about possible causes. Was there a lack of scientific management, overfishing, or was there something unknown phenomenon in nature, which led to the fish stocks disappearing. This presentation is a summary of a doctoral dissertation in which this topic was studied.