Proceedings of a workshop, the scientific reviews and the contributed papers presented at the symposium. The document presents a brief historical summary of marine research in the Gulf; reports the discussions, conclusions and recommendations of the different working groups on oceanography (physics, biology, chemistry and sedimentology) and on the fishery (fish and invertebrates); then presents the discussions of each multidisciplinary working group, centered around how the St. Lawrence system may be used as a natural laboratory which will contribute to the solution of major long-term problems of conservation of natural resources and of the quality of the environment.