18 O. Nordgaard. [No. 3 



Spirialis retroversus, 

 Polychæta, 

 Sagitta bipunctata, 

 Hydroida. 



From the above series it appears that the Oadus vir ens during 

 "the first year of its life chiefly feeds on plancton. G-enerally 

 speaking it may be said that the young coal-fish are satisfied with 

 the planctonic fare that offers, and if the latter falls short, resort 

 to the seaweeds, where they feed on amphipods, isopods, ostracods, 

 the young of gastropods and mussels (e. g. Mytilus edulis), indeed 

 even hydroids. Polychæta have appeared only as a great rarity. 

 Among plancton forms it is particularly the larger forms of cope- 

 pods that must stand treat. It is no small quantity a single young 

 coal-fish will consume in the course of a day. In a single stomach 

 I have counted ( 18 /io 1900, Turø) 6250 middle-sized specimens of 

 Calanus finmarchieus, Centropages typicus and Anomalocera nater- 

 soni. For the sake of comparison I shall mention one of my richest 

 plancton catches of copepods. On February 7th 1899 i caught in 

 the Ofoten Fjord with a Dr. Petersen's closing net that was kept 

 open from the depth of 250 metres to 200 m., the following cope- 

 pods: 



Calanus finmarchieus 1575 specimens 

 — hyperboreus 26 — 



Metridia longa 24 — 



Euchæta norvegica 9 — 



1634 specimens 



As the catching opening of the net is about 0.09 square metre, 

 the quantity of water that was fished through, is 

 0.09 x 50 = 4.5 cubic metre. 

 The number of copepods per cubic metre is consequently 



1634: 4.5 = 363. 

 I can, with considerable certainty, assert that the number of 

 copepods per cubic metre was not by far as great at the place 

 where the said young coal-fish had its hunting ground, but even if 

 such were the case, it was obliged, in order to fill its stomach with 

 the said number, to make a clean sweep of 



6250: 363 = about 17 cubic metres. 

 It is not likely that the young coal-fish should have tåken the 

 trouble of searching through such a large space of water. Turø 



