SOME PRELIMINARY OBSERVATIONS ON THE 

 MIGRATIONS OF THE EUROPEAN SALMON 



By W. J. M. MENZIES 



FISHERY BOARD FOR SCOTLAND, EDINBURGH, SCOTLAND 



With a view to tracing the migrations of 

 salmon in European waters the fish have 

 been marked at three stages in their lives, 

 viz., as smolts, clean fish and kelts. Smolts 

 and kelts have been dealt with when de- 

 scending to the sea and clean salmon chiefly 

 in salt water. Such operations were started 

 in Scotland about 40 years ago, and since 

 then have been extended to Norway, Ire- 

 land, England and practically all of the 

 countries bordering on the Baltic. 



Smolt marking has produced no evidence 

 of the movements of the salmon in the sea, 

 either when feeding or returning to fresh 

 water, except in the Baltic. It will perhaps 

 be most convenient to deal now with these 

 last results and with the other aspects of the 

 life of the fish in that sea, since they form 

 a self-contained community divided from 

 the salmon of the Atlantic by a line drawn 

 from Denmark to Sweden across the narrow 

 western neck of the Baltic. Investigations 

 have been made chiefly by Dr. Gunnar Aim 

 of Sweden and these, together with the work 

 of his countryman Dr. Nils Kosen, of Pro- 

 fessor Jarvi in Finland and others, he has 

 summarized in a publication of the Inter- 

 national Council for the Exploration of the 

 Sea (Aim, 1934). 



The results achieved in this small sea are 

 of particular interest as showing the con- 

 sistent yet somewhat complicated movements 

 of the salmon from their native rivers to 

 their feeding grounds and then back again 

 to the rivers. Put quite shortly, the mark- 

 ing of smolts and adult fish and the reading 

 of their scales show that the smolts from the 

 rivers on the west side of Finland, and from 

 the north and middle of Sweden proceed 

 down the Swedish coast to the southwestern 

 corner of the Baltic (Fig. 1). From the 

 north Finland rivers the smolts proceed 



down the other side of the Baltic, across the 

 mouth of the gulf of Bothnia and down to 

 the Polish and Pomeranian coast. This mi- 

 gration on the eastern side of the Baltic is of 

 special interest since these northern fish pass 

 the smolts and young salmon originating 

 from the rivers of Esthonia and Latvia. 

 The explanation seems to be that the latter 

 fish find an adequate quantity of the food 

 comparatively close to their native rivers, 

 but that a more far reaching migration, 

 equivalent to the migration carried out 

 by the salmon of the west Finnish rivers, 

 takes the northern Finnish salmon on 

 past these feeding grounds to yet better 

 areas further south. In their early stages 

 the little fish feed on Gammarus sp. and 

 later on Ammodytes sp. and no doubt small 

 herring also. 



The exact distribution of the small and 

 feeding fish in the southern part of the Bal- 

 tic depends upon the prevailing wind and 

 the spread of the food supply. The smolts 

 of the current year arrive at the south of the 

 Baltic in the autumn months and thus take 

 approximately three to five months for a 

 journey of up to eight hundred miles. At 

 first in general the Swedish smolts are found 

 in the southwestern corner but later they 

 may move out round Bornholm and towards 

 the Danish, German and Polish coasts where 

 an intensive fishing with both lines and nets 

 is carried out for them in the late winter and 

 spring months. The majority of the catch 

 are ' * mielnice, ' ' as they are locally called, or 

 in other words young salmon in the pre- 

 grilse stage. They are from 40 to 50 cm in 

 length and weigh from about 1| to 2 lb. 

 After April or May they are lost even in 

 this small sea. No doubt some journey north- 

 wards and return to the rivers as grilse, but 

 many others remain somewhere in the south- 



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