The Exploitation of the Spiny Dogfish (Squalus acanthias L.) in European Waters

The present paper is a short account of the state of the stock in recent years of Squalus acanthias in European waters. The basic material is the catch statistics from Bulletin Statistique (ICES), the Norwegian spur-dog taggings, and certain catch/effort data from the Norwegian long line fishery for spur-dog. The fishery has expanded rapidly since the World War II and the annual yield is now (1961) about six times higher than in 1945. The bulk of the catch is shared between four countries: England, Scotland, France, and Norway. The main part of the yield originates from the waters around Shetland (summer) and the Norwegian west coast (winter). Extensive taggings in these localities show a free intermixing of the fish between these areas. However, occasional recaptures from the same taggings are recorded from the Barents Sea, Lofoten, the North Sea and Skagerak, the waters around Ireland, the English Channel, and in the Bay of Biscay. It is, therefore, possible that there exists only one stock common to the Northern and Western Europe. From a quantitative analysis of the tagging data it appears that the estimate of the average total instantaneous mortality rate in the years 1960-1963 amounts to 0.72, and this high figure is interpreted as a danger signal. A certain measure of the catch per unit of effort was obtained from various dealers by comparing the landings with the amount of bait used. The series, comprising the years 1957-63, shows a heavily declining stock. Using Shaeffer's model for stock assessment, the obtained series of catch/effort, and the catch statistics froim Northern Europe, a maximum equilibrium catch of about 50.000 tons is found. This level was, practically speaking, reached in 1961. The available data are not considered sufficient for a precise stock assessment; but one important fact does emerge :The present exploitation of the stock of Squalus acanthias in European waters is undoubtedly very high