Phosphate and Fisheries

Landings of the spurdog, Squalus acanthias , at Mevagissey reflect the changes in phosphate at the neighbouring International Hydrographic Station Ei. It is suggested that commercial landings of rays and skates ought to follow major changes in nutrient content of the overlying water with a time lag of some years. Fishery statistics for English Channel ports support this view. The dependence of the bottom in-fauna upon the fertility of the overlying water is also discussed. Proposals to improve commercial fisheries by artificially fertilizing considerable areas of the open sea are critically examined. Such artificial enrichment is considered to be grossly uneconomic unless fishing becomes pisciculture in which weeding of unwanted algae and control of unwanted pests—competing predators and parasites—is undertaken.