Presents information on a study which examined the responses of the Port Jackson shark, Heterodontus portusjacksoni and the stingaree Trygonoptera testacea, after being transferred to diluted in seawater. Examination of the plasma ionic status of elasmobranchs or sharks; Details on the erythrocyte fluids of marine elasmobrancs; Changes in the erythrocyte ionic composition of elasmobranchs; Body weight of the sharks.