Tunny in the North Sea

Abstract

AMONG the notes in the “Calendar of Nature Topics” in NATURE of July 15 are two paragraphs on the occurrence of tunny in the North Sea. This fish seems, indeed, to have become much more common there in recent times than it was some decades ago. A fisherman here, now concerned with Indian fishery investigations, recently told me that he remembers perfectly well that it was in the year 1911 (well-known also by an exceptionally heavy storm) that the big creatures, hitherto unknown, first came under the attention of those engaged in herring fishing on the North Sea. This particularly interested me, as 1911 was an exceptional year in its very warm and dry summer. My plankton investigations on the light-vessel Haaks off Den Helder, during the years 1910–1912, showed that the influence of this heat period was great also on the temperature of the sea and the development of the plankton. Diatoms, peridinians, and copepods, one after the other, successively attained maxima several times higher than in normal years1 and a southerly form like Doliolum nationalis pushed forward in great numbers to the latitude of Den Helder. Would it be possible that the tunny also in this remarkable year found its way into the North Sea and in subsequent summers has continued to frequent these northerly waters? It would be interesting to have further information upon the statement of my fisherman.