Long term changes in spawning volume for Baltic Sea cod (Gadus morhua)
(English)Manuscript (preprint) (Other academic)
In the brackish Baltic Sea, cod (Gadus morhua) can reproduce only in a few deep areas, of which the Eastern Gotland basin and the Bornholm basin are the most important ones. Successful spawning requires oxygen concentrations larger than 2 ml r-1 and salinity larger than 11. The water domain that meets these requirements is referred to as the cod spawning volume. Salinity and oxygen data were collected during the period 1905-1997 and 1923-1997 from the Eastern Gotland basin and the Bornholm basin respectively. They have been analysed for changes in spawning volume over time. For each sampling occasion the spawning volume was calculated based on depth specific vertical distribution of salinity and oxygen concentration, combined with bathymetric data. The Bornholm basin constitutes a stable but limited spawning area for cod, contrary to the Eastern Gotland basin where the spawning volume is more uncertain but can be much larger. The estimated spawning volume decreased over time in the Eastern Gotland basin. This change is probably caused by increased deepwater oxygen demand due to increased organic material load from primary production. The latter is an effect of the ongoing eutrophication.
cod, spawning volume, Baltic Sea
Social Sciences Interdisciplinary
IdentifiersURN: urn:nbn:se:liu:diva-79296OAI: oai:DiVA.org:liu-79296DiVA: diva2:540284