Notes on the swim-bladder physiology of cod (Gadus morhua) investigated from the underwater laboratory "Helgoland"

Abstract

In situ sampling of gas from cod swim-bladders took place during a fortnight's saturation mission with the underwater laboratory "Helgoland" in May-June 1975. These samples were compared to those done by the conventional method of transporting the fish to the surface for sampling. Based upon these in-situ measurements, the mean O2-concentration was 55.7% in buoyant cod at 15 m depth. Repeated sampling of the same fish showed a change in gas composition. Compared to the conventional method of transporting fish for sampling to the surface, in-situ sampling gave results with less variation, and indicated that surface-sampling does not give the correct gas composition of buoyant fish at depth of catch. © 1977 Biologischen Anstalt Helgoland.