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

摘要

The present paper is a short account of the state of the stock in recentyears 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 datafrom the Norwegian long line fishery for spur-dog.The fishery has expanded rapidly since the World War II and theannual yield is now (1961) about six times higher than in 1945. The bulkof 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 inthese localities show a free intermixing of the fish between these areas.However, occasional recaptures from the same taggings are recorded fromthe Barents Sea, Lofoten, the North Sea and Skagerak, the waters aroundIreland, the English Channel, and in the Bay of Biscay. It is, therefore,possible that there exists only one stock common to the Northern andWestern Europe.From a quantitative analysis of the tagging data it appears that theestimate of the average total instantaneous mortality rate in the years1960-1963 amounts to 0.72, and this high figure is interpreted as adanger signal.A certain measure of the catch per unit of effort was obtained fromvarious 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 ofcatch/effort, and the catch statistics froim Northern Europe, a maximumequilibrium catch of about 50.000 tons is found. This level was, practicallyspeaking, reached in 1961.The available data are not considered sufficient for a precise stockassessment; but one important fact does emerge :The present exploitationof the stock of Squalus acanthias in European waters is undoubtedly veryhigh.