_ 25 — JOH. HJOET AND C. G. JOE. PETERSEN 



the kernel of the matter, regarded from a practical standpoint. Speaking practically, it is quite 

 indifferent whether the historical development has brought about a decrease of a fishery or not, 

 if we can only state the means by which it may be restored. In Petersen's opinion, this can 

 be done in the case of the plaice (see Appendix H). 



The Danish investigations have shown, by the marking of plaice in the North Sea, that 

 an extraordinarily large number of marked fish are recaught by the fishermen and returned, 

 so that we may conclude therefrom, that it is above all man who is weakening the stock, and 

 that we can increase the production of the yearly quantities for the use of man by suitable 

 regulations, in this case especially, by forbidding the landing of plaice under a certain size. 



Petersen has attained to these results only after many years' investigations, as it was 

 necessary to study the life of the plaice and also the influence of the fishery on it, and at the 

 same time to ascertain in what manner man could best interfère in the matter. By reason of 

 the great tenacity of life displayed by the plaice and on account of the manner in which its 

 various age-groups are distributed in the sea, he has especially recommended the prohibition of 

 the landing of the smaller fish and believes that this will be the best method. But how the 

 matter should be arranged as regards other species to be protected, is a question which 

 can only be answered with regard to the North Sea, when an exact knowledge of the fisheries 

 and of the natural history of the fishes has been attained. Various regulations can be thought 

 of (width of meshes, close periods, closed areas etc.), but which of these would give the desired 

 results in a given case, would require such a thorough investigation as has been made in 

 Denmark in the case of the plaice. 



d) It has been shown above, how it may be expected to improve the fisheries of a certain 

 species by protective legislation, but the idea of finding other ways, by which the results 

 of the productivity of the sea may be increased, is also at hand, and for a long time tlie idea 

 of artificial rearing of the eggs of fishes has played a great part ia discussions. 



As will be described more closely in Section III, concerning the natural history of the cod, 

 investigations are at' present being arranged in Norway to determine, if the setting out of 

 pelagic young fish, just hatched, into Norwegian fjords exercises any influence whatever on the 

 quantity of young cod some months old, and if the local stock in these fjords is thereby 

 markedly increased compared with other neighbouring fjords where no young is placed. For 

 the large stock of cod in the ocean, such artificial propagation of pelagic young fish will 

 scarcely have any importance whatever. 



There is nevertheless another way to obtaia greater usefulness from artificial propagation ; 

 namely, by rearing small young fish until they are so large that they remain on the bottom 

 and are to some extent stationary; when they are then set out, they remain on the spot and 

 are not carried miles away by the currents, as happens otherwise to the small pelagic young 

 fishes. The small plaice become stationary bottom-animals at about 1 cm. long and when some 

 months old; if they were reared in quantities and set out when 1 cm. long and some months 

 old, much would be attained. Such experiments have already been undertaken at various places 

 and been successful with a small number of individuals. Endeavours similar to these have 

 already been taken up in the program of Commitee C 2 and work is being carried on in various 

 countries in this direction. 



Appendix G 4 



