Some Atlantic cod Gadus morhua in the Baltic Sea visit hypoxic water briefly but often.

Individual behaviour of Atlantic cod Gadus morhua in the presence of hypoxic water was measured in situ in the vertically stratified Bornholm Basin of the Baltic Sea. Considering all recaptured individuals, the use of hypoxic habitat was comparable to data derived by traditional survey data, but some G. morhua had migrated towards the centre of the c.100 m deep basin and spent about a third of their time at oxygen saturation <50%, possibly to forage on zoobenthos. Maximal residence time per visit in such hypoxic water was limited to a few hours, allowing for the digestion of consumed prey items in waters with sufficient dissolved oxygen.