24 
the Danish seas as small or middle-sized fish. Dr. Th. Mortensen has con- 
ducted these investigations at Bornholm this year, on board the Sallingsund; 
a report of them will be published later on. That all the Baltic cod have 
immigrated through the Danish seas, seems to agree very well indeed with 
Dr. R. Lundbergh's account of the fisheries in the Baltic Sea ("Royal Com- 
mission on Trawling”. App. p-. 464, 1885) for several fishes, among which 
were cod and dab. The fish will be quite common there in certain years; 
but suddenly they disappear from the sea for years, and he is unable to 
give any reason for it. When everything depends on an immigration through 
the narrow Belts, it is easy to understand that the winds and the currents, 
which are so changeful, in one year can further, but as well in other years 
can check the immigration. The stock therefore becomes very different in 
the different years, particularly in the inner parts of the Baltic. On the 
whole, the stock of fish with pelagic eggs in the Baltic Sea is most likely 
dependent on an immigration from the Cattegat, and there are scarcely 
many species that manage these long migrations so well as the fry of the 
eel seems to do. — 
We see then the cod in Denmark at various times of the year under- 
take long migrations, and on different stages of its development stay in 
different seas. G. 0. Sars in his well-known '""Indberetninger” has just the 
same view of the cod on the shores of Norway. He meant to have proved 
that the cod bred in the Lofoten every winter, but nevertheless the same 
fish was living in the summer far northward, in some years as far north 
as Spitsbergen. It now seems as if these theories of his will come to life 
again. But when our cod leave the Cattegat they do not, at any rate, go 
to the Lofoten; they rather, I should say, go to the North Sea, the Faroe 
Islands, and Iceland. But. at present I know nothing of this with certainty. 


