A Fish-Farming Experiment in a Sea Loch

Abstract

Introduction IN 1941 it was suggested in NATURE¹ that it might be possible to increase our food supply by increasing the fertility of suitable parts of the sea, and a scheme for a preliminary investigation was outlined. It was based on the assumption that the fertility of the sea is largely dependent on the same factors as that of the land or of freshwater fish ponds, namely, light and plant nutrients, and that an improvement could be obtained by supplementing with artificial fertilizers the amount of nutrients available for plant growth. Of these, nitrate and phosphate are known to limit the growth of phytoplankton in the sea, and it was assumed that the addition of sodium nitrate and superphosphate would lead to: (1) a higher level of plankton productivity; (2) a greater density of bottom fauna; and (3) an increased growth-rate of fish. (After we had started our work we found that the effect of fertilizers on the first link in this chain had been tried out in oyster polls in Norway so early as 1908, but no results were published until the fertilization experiments of Gaarder and Spärck in 1932^2,3. They found that the addition of dissolved phosphorus and nitrogen in 5–10 times normal winter sea values led to an increase in nano- and zoo-plankton and also to a good growth of oyster larvæ.)