Chemical properties of the waters in Trevor Channel and Alberni Inlet during late summer have been applied for an estimate of basic productivity. Based on the assumptions that the deep water in the system is renewed once per year and that the observed conditions in September represent the state of the water just before renewal, the oxygen deficit and the phosphate surplus in the deep water have been used as a measure of the organisms decomposed during the year. Oxygen depletion gives 28 g/m2of plankton per year as carbon; phosphate liberation gives 31 g/m2. From fishery statistics it was estimated that the herring in Barkley Sound consume about one-quarter of the available plankton and all plankton feeders consume about one-half of the total. This would increase the above figures of productivity to 56 g/m2and 62 g/m2, respectively. These values are probably a minimum annual productivity inasmuch as basic assumptions may not be completely fulfilled. Regeneration of nutrients in the surface layer, and some renewal of deep water by mixing and circulation, probably occur throughout the year.