For a long time, scientists, fishermen and the general public have asked themselves: Why has Baltic cod become so small and lean?
Now Yvette Heimbrand, a researcher from the Swedish University of Agricultural Sciences (SLU), believes that she may have part of the answer. In her doctoral thesis, which she presented in the spring, she has investigated cod’s auditory stones, also called otoliths. Those otoliths can provide answers to how old cod is – and how fast or slow it has grown. By analyzing codotoliths from 1927 to 2010, Yvette discovered a pattern: There is a clear link between the size of cod and the amount of oxygen in the Baltic Sea…