Egg mortality in recruit- and repeat-spawning cod: an experimental study

Experiments on the reproduction of individual Norwegian coastal cod and for the Arcto-Norwegian cod were conducted during the years 1982-92, and the year 1995 respectively. The experimental fish used were held in captivity over several consecutive spawning seasons to investigate differences in egg mortality within and between spawning seasons. Egg mortality was found to be restricted to the first days of incubation. For coastal cod a significant reduction of egg mortality was documented from first to multiple spawning from the same cod female. Similarly, a decreased egg mortality was found in the first egg batches compared to the last ones. Preliminary results on Arcto-Norwegian cod showed similar trends. The results are discussed in relation to egg surveys, management of spawning stocks and the combined match/mismatch-maternal recruitment variability model