— 7 — JOHS. SCHMIDT 



the young it naturally mainly takes the smaller sizes which are not very rapid in their 

 movements; but that it can also catch large quantities of the older, swifter young fish 

 is seen for example from St. 125, 1905, July, at the Fœroes. No information is given in 

 general by the young-fish trawl regarding the early, larval stages with the yolk-sac 

 yet attached, as these larvae are so delicate that they are usually destroyed or spoilt in 

 the trawl. The young-fish trawl is specially well adapted for the capture of the post- 

 larval pelagic stages, and as will be mentioned later it is chiefly these stages which 

 form the basis of the present work. 



The duration of the hauls was very various: from 10 minutes to several (6) hours. In 

 1903 short hauls of 10 minutes were much used, but later I preferred to make them 

 longer, usually one half or whole hour, and hauls of several hours were common especially 

 in deep water. 



The young-fish trawl was of course always towed horizontally, and as mentioned at a 

 rate of ca. 2 miles per hour; from the duration of the haul we can thus judge to a 

 certain extent how great a distance was fished (from ca. V2 to ca. 12 miles) and thus 

 compare the relative quantity of young fish in the different waters. There can naturally 

 be no question of great exactness, but certain comparisons may nevertheless be drawn. It 

 may be added also, that the fishing qualities of the young-fish trawl are so great that we 

 are to a certain extent entitled to draw conclusions from negative hauls, i. e. in which 

 none of the fry were taken, with regard to the distribution of one or other species. 



The depth at which the young-fish trawl works in pelagic hauls, if the speed of the 

 vessel is always the same, is determined chiefly by the length of wire out. Other 

 conditions however also have some influence, for example, the direction and strength of 

 the currents, but their effect is usually unknown. I have therefore not given the depth 

 under the surface for the separate hauls, but the length of wire out. It may be mentioned 

 however that, from some experiments made in the Skager Rak in the summer of 1907 

 with the "control depth-measurer" ^ invented by Captain Clausen of the Danish Navy, 

 which was carried on the poles of the net, the depth in which the trawl fishes is in 

 general almost equal to half the length of wire out, but the slightest variation 

 in the normal number of turns of the vessel's screw at once alters the conditions. Further, 

 the apparatus is relatively deeper down naturally when a lot of wire is out than when 

 there is but little, as the weight of the wire begins to tell. 



Our investigations on the distribution of the young bottom stages have been of 

 great assistance in ascertaining the distribution of the pelagic stages ^. The species living 

 in deep water were taken by means of the young-fish trawl or the ordinary otter -trawl 

 with a fine-meshed net over the cod-end. For the fry which live in quite shallow 

 water in the tidal region amongst the algal vegetation (e. g. of Gadus virens, poUachius 

 and cullarias), we have chiefiy used the Danish "eel hand-seine", a large small-meshed 

 seine, which was usually set out from a row boat and then dragged on land. An extremely 



' To be obtained from tbe firm Corkbijus Knudsen in Copenhagen. 



- It is evident in the first place that it is of great interest to compare the distribution of the pel- 

 agic stages with that of the young bottom stages. Further, for the species whose earliest bottom stages 

 live in the tidal region in quite shallow water, it is clear that they are easier to detect in these stages 

 when they are collected together within a quite narrow and shallow belt, then when pelagic they are 

 scattered over wide areas. 



