Great Central Lake is one of many large and deep lakes which exist in the mountainous spine of Vancouver Island. Having a maximum depth of 294 m, the lake is the second deepest on the island. The mountainous terrain is composed of plutonic rocks of the Mesozoic era and the surficial deposits in the drainage basin are glacial or glacio-marine in origin. The climate is cool and wet in the winter and warm and dry during the summer. Snow is rare at the lake's elevation but there are accumulations of snow at higher elevations in some years. There is extensive logging in the watershed, but shoreline development is extremely sparse and limited to the outlet area. There are no settlements in the drainage basin. While the lake serves as an excellent place for recreational pursuits (e. g. swimming, boating, sport-fishing), its importance to the regional economy and the science of lake management rests with the initial development of the Lake Fertilization Component of the federal/provincial Salmonid Enhancement Program. One of the important species of Pacific salmon (sockeye or Onchorhynchus nerka) spends its first year of growth in many lakes in the Pacific northwest region of North America and their survival at sea (where they grow to maturity in 3 years) is dependant on their size and condition when they leave the lake after a spring and summer of feeding on zooplankton. The hypothesis that the size and condition of the sockeye during the first growing season could be enhanced through fertilization of the surface waters with inorganic nitrogen and phosphorus and that this would lead to greater returns of sockeye to be harvested in the sea when they returned was tested in Great Central by the Pacific Biological Station from 1970 to 1976 (1). The numbers of returning fish increased more than 7 times in those early trials and this success led to the fertilization of many sockeye rearing lakes along the coast of British Columbia (Q).