Factors influencing the Size of the Year Classes in the Arcto-Norwegian Tribe of Cod

Abstract

1. The quantitative occurrence of eggs and larvae of the Arcto-Norwegian cod in the coastal and bank areas of northern Norway during the years 1948-1956 has been studied. 2. There is no correlation between the abundance of eggs and larvae and the relative strength of the corresponding year classes of cod in the commercial catches. 3. There is no increased mortality at any stage in the early life history of the cod. 4. The following conditions seem to be of importance for establishing a rich year class: a) a long spawning period, b) a proloilged hatching or spawning late in season, c) an extention or northward displacement of the spawning centre, d) a successful transport of the eggs and larvae from the spawning area to the nursery grounds by currents. These conditions seem more or less to be fullfilled for the year classes 1948-1950, which now dominate the commercial catches in the Barents Sea and adjacent areas.