Comparative studies of inorganic substances in the blood of fishes from the Scagerac Sea

The concentrations of the main plasma inorganic electrolytes Na+, K+, Ca2+, Mg2+, Cl‐ and and PO43‐ have been determined for different orders of marine fishes. For Na+ and Cl‐ a typical decrease was found when passing from cyclostomes, holocephalans and elasmobranchs to teleosts. The concentrations of K+, Ca2+ and Mg2+ showed a similar trend except that there was a rise in the teleost group, which showed a large range of variation for these three ions. In the case of PO43‐ no significant differences between groups were found.