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Part III. — Fifteenth Annual Report 



which form a principal source of the food of pelagic fishes, as the herring 

 and mackerel, as well as of the larval and post-larval stages of many other 

 forms. They appear also to be correlated with the distribution of certain 

 species, which are not in their adult condition subjected to their drift- 

 action. It is not improbable that the successive appearance of the shoals 

 of herrings, whose presence gives rise to the spring fishing on the western 

 and northern coasts of Scotland, the summer fishing on the east coast of 

 Scotland, and the autumn fishing off the Norfolk coast, is connected with 

 the existence of the current which will be shown to exist parallel to these 

 coasts, and which moves in the same direction. Moreover, a knowledge of 

 the currents referred to may help to explain the formation of banks, espe- 

 cially in the southern and eastern parts of the North Sea, which are 

 frequented by great numbers of the food fishes. 



This paper will therefore deal, in the first place, with the movements of 

 the surface water in the North Sea, as shown by the drift-bottles and 

 drift-slips, and their relation to tides and winds ; and, in the second place, 

 with the effect of these movements so far as concerns the sea fisheries. 



II. THE DIRECTION AND RATE OF THE CURRENTS. 



(1) The Course of the Drifters. 



The experiments were begun in September 1894, and have been 

 continued up to February of the present year (1897), thus embracing a 

 period of about two years and a half. During this time the number of 

 bottles set adrift in the North Sea, or to the north and west of it, was 

 2074, and the number of wooden slips set adrift was 1479; about 14 

 per cent, have up to the present been recovered, the great majority 

 being bottles. There is evidence, which need not be particularised, 

 that all the drifters which were found were not returned. Most 

 of them were put overboard from the fishery steamer * Garland,' others 

 by H.M.S. 'Jackal' and H.M.S. 'Research,' others by fishing-boats 

 engaged in the deep-sea fishery ; many by the steamers belonging to 

 Messrs Currie & Co., Leith, while on their passage to Christiansund and 

 Hamburg ; by the steamers belonging to Messrs Geo. Gibson & Co., 

 Leith, on their voyage to Rotterdam, and by steamers belonging to the 

 North of Scotland Steam Shipping Company. 



The courteous assistance thus rendered by the firms and gentlemen 

 named materially aided the work 



In almost all cases a number of drifters, from three or four to over 

 twenty, were thrown overboard at the same place ; and in the Tables 

 appended to this paper (p. 377) the dates and places of immersion and 

 recovery are given. The area where they were put into the sea extends 

 from between the Shetland and Faroe Isles on the north to a line running 

 from a point off Flamborough Head to the Hook of Holland on the south. 

 The great majority were put away on the east coast, but a considerable 

 number also at intervals along lines between the Isle of May on the one 

 hand and Christiansund and Hamburg on the other. The following 

 shows the numbers put away in the various months of the period : — 



Jan. Feb. Mar. Apr. May. June. July. Aug. Sept. Oct. Nov. Dec. 

 1894, 24 180 114 59 



1895, 38 127 224 70 26 50 105 . 



1896, • 204 4 98 175 310 540 553 267 292 



1897, 110 



The number set adrift on the east coast of Scotland, within 20 miles 



