— 142 — 



The manner in which the fishery for the silver eel is carried on in the Baltic countries 

 is thus able to give us important information regarding the direction of the migration of 

 the eel. Further, in quite recent years we also have the results of some marking- 

 experiments, which are of great interest as they show directly and surely the direc- 

 tion taken by the migrating silver eels in the Baltic. They also give us information on 

 the speed at which the eels migrate, concerning which we could obtain information in 

 no other way. Dr. F. Trybom of Sweden has given a very interesting report on the eel 

 marking-experiments in Sweden and Finland, the main results of which are as follows ^ 



All the eels were recaptured at places lying nearer to the open sea 

 than the spot at which they were set out, and it is thus incontestably proved that 

 the direction of the migration is out from the Baltic. It further appeared that 

 the smallest eels (yet all silver eels) migrate with as great a speed as the 

 large. Dr. Trybom comes to the conclusion based on a considerable number of exper- 

 iments, that the silver eels not rarely traverse a distance of at least 15 kilo- 

 meters per day (and this for so long a period as 17 to 30 days). In most cases the 

 eels seemed to follow the line of the coast in their migration southwards in the 

 Baltic along the Swedish coast, but there are also cases which show that the eel does 

 not hesitate to cross over depths of at least 60 meters. 



These eel marking experiments have thus produced splendid results. The 1905 

 experiments have further shown that the Baltic eel in their autumn migration leave the 

 Baltic. Thus two specimens marked in 1905 in the Baltic (Finland, Swedish east coast) 

 were recaptured in Danish waters, the one in the Sound south from. Copenhagen, the 

 other on the east coast of Jutland at Helgenaes^ 



The latter had wandered a very great distance, viz. from Tvärminne in Finland, 



1 F. Trybom, Âlmarkningar i Üstersjön 1903 och 1904 (Svenska hydrograf.-biol Komniissionens Skrifter, 

 1905). The marks were small numbered silver discs fastened to the dorsal fin of the eels. Practically all the 

 specimens marked were silver eels. The most northerly part of the Swedish east coast, where marked eels 

 were set out in 1904, was Grisslehamn (off Aland Island, north of Stockholm) were 70 eels (length 58— 90 cm.) 

 were set out on Sept. 24th, 1904. So marked eels were also .set out on the Swedish coast at Arko in East 

 Gothland on Oct. 3rd, 1904 and 50 at Kivik in East Skâne on Oct. 8th, 1904. Of these 15-6, 18-75 *"fi '*% 

 respectively were recovered. At Tvärminne in Finland Prof. Palmen set out in all 132 eels in Aug.-Sept. 1904. 



All the eels marked in Sweden migrated from the north southwards along the Swedish east coast and 

 some thereafter westwards along the south coast of Skâne. 



A few examples from Dr. Trybom's report deserve to be mentioned. 



1. One specimen set out at Grisslehamn on Sept. 24th, 1904 was retaken on Nov. 14th of the same year at 

 Kivik in Skâne. In 51 days this eel had thus traversed at least 650—680 kilometers, which gives a speed 

 of at least 13-3 kilom. per day. 



2. Two specimens set out at Arko (East Gothland) on Oct. 3rd, 1904 were retaken on Nov. ist and 2nd 

 1904. In 29 — 30 days they had thus traversed at least 450—480 kilometers, which gives a speed of at 

 least 15 — 16 kilom. per day. 



3. One specimen set out at Helsingfors in Finland on Aug. 28th, 1904 was retaken on Sept. 22nd at Björkö, 

 north of Stockholm; another set out at Hangö in Finland on Aug. iilh was recaptured on Sept. i6th off 

 the archipelago at Stockholm. Both these Finnish ei.-ls had thus undoubtedly migrated right across the 

 Baltic from Finland to Sweden. 



2 These results were reported in "Dansk Fiskeritidende" 1905. The first eel w.is marked on Sept. 10th, 

 1905 at Bergkvara (Kalmar Län, Swedish east coast off Öland) and was recaptured on Sept. 29th south from 

 Copenhagen. The second was marked at Tvärminne in Finland and was retaken on Nov. 1 6th at the S. E. end 

 of Helgenaes on the east coast of Jutland. 



