SOME RESULTS OF THE INTERNATIONAL FISHERY INVESTIGATIONS. 453 



work has been concerned. After the hatching of the larva from the 

 egg there is a period of growth of which little is known. Some 

 weeks after hatching the "metamorphosis" of the larva is effected. 

 The little fish now takes on the shape of the adult, and gradually 

 assumes the habits and food of the latter. During the period of 

 juveuescence the life history must be studied in the sea itself, and the 

 growth and migrations observed in specimens taken in the most diverse 

 localities by means of special fishing apparatus. Neither the com- 

 mercial nets of the fishing fleet nor the older dredges or " townets " of 

 the naturalists afford any assistance in these investigations. Altogether 

 new fishing apparatus have had to be devised, and it has been necessary 

 to carry out researches far out at sea, in regions where fishery work 

 was, under the older methods, usually quite impracticable. 



Such investigations have been carried out by the naturalists of 

 the Danish, Norwegian, and German sections of the International 

 organization by means of specially designed fishing apparatus. The 

 " Scherbrutnetz " was designed by Ehrenbaum and Strodtmann,* 

 of the Heligoland Biological Station, for the capture of larval fishes. 

 This instrument is a very large townet with a square opening. The 

 special feature of the apparatus is the " sheering-board," a large board 

 attached to the lower edge of the mouth of the net, and inclinable at 

 any angle ; by means of this contrivance, which acts in the same way 

 as the otter-board of the commercial otter-trawl, the net can be towed at 

 any desired depth. The " young-fish trawl " of Tetersenf is a still more 

 effective instrument, which is constructed on the principle of the large 

 otter- trawl, and is able to fish at the sea bottom or at any depth from 

 the surface. The net, being composed of material with a very fine mesh, 

 is adapted to catch very small fishes. 



The invention and use of these two forms of fishing apparatus are so 

 important for the investigation of the pelagic or young free-swimming 

 stages of edible fishes that one might almost say that their application 

 begins a new era in fisheries research. The older surface townet 

 captured pelagic larval fishes only in very small numbers, and it was 

 always difficult to use this instrument with much success at the bottom 

 or at intermediate sea levels. We know now that results obtained by 

 the use of ordinary townets in the past were totally misleading so far as 

 affording reliable information as to the distribution and abundance of 

 young stages of sea fishes. Joh. Schmidt,'): for instance, gives a record of a 

 haul of the young-fish trawl taken from the Danish investigation steamer 

 Thor off the coast of Iceland, at a depth of 79 metres (about 40 fathoms), 



* Wissensch. Meeresuntersuch. , Hd. i., Abteilumgen Helgoland. 



t Skrifler af Kommissionfur Ilavuncrsogelsen, Nr. 1, 190-4. 



X Meddelcher Komm. Havundcrsijgelser, Ser. Fiskeri, Bd. i. No. 4, 1905. 



NEW SERIES. VOL. VII. No. 5. 2 H 



