On the decline of eastern Baltic cod: we need to take more holistic views into account. Reply to Brander (2022) comment on Svedäng et al. (2022)

Abstract

Abstract Explaining the recent decline of eastern Baltic cod (EBC) remains scientifically challenging. Brander proposes in a comment to Svedäng et al. that the observed trend in oxygen in SD 25 supports the idea that juvenile cod are balancing the physiological cost of living under mild hypoxia by offsetting the risk of being eaten by diving seals and cormorants in shallower water with more oxygen. There are a number of objections to this conjecture, besides the fact that supporting observations are missing. Hence, it is difficult to reconcile the long-term development of EBC under varying oxygen conditions with the hypothesis that a small reduction in oxygen content can explain the current strong and uniform decline in growth observed in the entire southern Baltic Sea.