II. METHODS OF WORK AND GENERAL RESULTS 



A. Methods of work and apparatus 



It can be readily understood that, ever since fisheries investigations have been insti- 

 tuted at all, endeavours have also been made to bring a variety of methods into use for the 

 investigation of the nature and amount of the fishes within the area investigated; it was 

 immediately felt that advance had to be made according to a fixed plan, if general conclusions 

 were to be in any way obtained from the results of the investigations. It would be quite 

 ideal naturally, if we knew what species and how many individuals of each species were 

 present in the waters to be studied, how quickly they grew and so on. For a small inland 

 sea such an investigation is often easily carried through; it is therefore easy to understand, 

 why such investigations have already been carried much further with regard to fresh water 

 than for the sea (rational practice). In the investigation of large areas of the sea again, 

 the matter becomes more difficult and more complicated, as it is not so easy to gain a view 

 over the momentary fish-quantum, and as fishes wander to and fro as a rule. Accordingly, in 

 order to obtain as good results as possible in such an area, various methods have of necessity 

 been resorted to. We shall mention the most important of these methods in the following. 



One of the earliest endeavours to institute systematic investigation of the fish-quantum in 

 a section of the sea, was certainly V. Hensen's quantitative hauls of pelagic fish- 

 eggs with apparatus specially constructed for the purpose; his methods are still in use, thougli 

 in more or less modified form, and advance has been further made on the road indicated 

 by him, especially after the apparatus had been enlarged; nothing is now easier than to 

 demonstrate the presence of a species of fish at the spawning time by the capture of pelagic 

 eggs. Though it has not been found easy to calculate the existing fish-quantum by means 

 of vertical hauls and purely quantitative determinations, yet the fishing for eggs in tliis 

 manner and also by means of horizontal hauls has everywhere yielded splendid results. 



Nevertheless, in order to ascertain the resorts of spawning fish witli greater accuracy 

 than can be attained from the pelagic eggs — not all fishes also have pelagic eggs — it has 

 been necessary to proceed to the capture of the fishes themselves with real fishing apparatus. 



The next thing necessary was to study the catches of the fishermen, as these can 

 easily be procured at certain places and at certain times. In this way, good information has 

 been obtained concerning the mutual quantitative relations of the fish-species occurring in the 

 hauls, and it has been possible to study their size at the beginning of maturity, and 

 amongst other things, to ascertain their food by investigation of the contents of the stomaclis. 



