I. The Biology of the Cod in the Danish Seas. 
I. Investigations in 1899 and 1900. 
In the year 1900 our investigations into tlie Biology of the Codfish in 
the Great Belt commenced in the month of March. The very first thing 
we wanted to know was, where the cod lived in the greatest numbers. On 
the 27. of March, therefore, we placed 600 hooks in the water, NW of 
Sprogø, on 4—10 fathoms; they were baited with herrings. After the lapse 
of 2 hours, part of the line was underrun, but there was no cod on it; the 
hait, however, was still in proper order, and so we left the hooks where 
they were. The 28. of March we had a boiler-test on board the Sallingsund, 
and we did not look after the hooks till the 29th. . The catch was 29 cod, 
3 plaice, and 13 common dabs. We considered this a very poor catch, and 
set 600 other hooks with herrings, like the former, SE of Sprogø, on 7—24 
fathoms of water, down the slope of the deep channel. After the lapse of 
3 hours, they were taken up again, and gave 130 cod, 1 whiting, and some 
plaice and common dabs. It was here, consequently, that the cod stayed; 
they were taken, particularly, on the outmost 400 hooks, and here they 
would bite immediately, also in the day; it being rather dark down here, 
with but little difference between day and night. The fishermen never set 
their hooks at this place, for fear of losing them in the strong current, and 
on the stony bottom, but more particularly, I think, because they do not 
know that there are many codfish here, at times, and that the hooks need 
only stand out 2—3 hours a day; for then all the bait is eaten away. — 
None of the cod we caught, were under 12 inches in length; most of them 
were between 13 and 18 inches, and only one was 25 inches long. 
In order to learn whether there were no smaller cod out here, we set, 
on the 31. of March, 600 hooks baited with worms (Årenicola marina), at 
