84 DR. Petersen's report of the Danish biological station. 



Fishing appears to be carried on entirely by means of seines, of 

 a fixed pattern of mesh, and during a season which opens on the 

 1st September, while a law has for some time been in force whereby 

 the sale of plaice less than 9| inches long is prohibited, though 

 there is no means of preventing the use of undersized fish for agricul- 

 tural purposes. However, it does not appear from anything in the 

 Eeport that there is any depreciation in the annual take, though 

 the annual drain on the stocking power of the outside fish is so 

 considerable, and to all intents and purposes wholly uncompensated by 

 the return of mature fish to the open sea. * 



Human intervention is therefore here required, not to arrest a 

 decrease of the general supply, but to effect an increase in the number 

 of large fish, for of the small there seem to be enough and to spare. 

 The problem is really, as appears from the Report, how to get enough 

 fish into the inner broads, i.e., Liv broad and its subsidiary lagoons, 

 which, forming about one-half of the total area of the fjord, are 

 practically never reached by plaice under natural conditions. 

 Petersen's observations lead him to the knowledge that the young fish 

 move very slowly up the fjord, and reach the inner expanses, if at all, 

 only in very inconsiderable numbers. 



The reason is not far to seek, for, in the first place, nearly all the fair- 

 sized individuals find their way into the hands of the fishermen ; while 

 if any escape they must, to reach the inner waters, traverse dense grass- 

 fields (zostera), whither the plaice " come but rarely, and where it has 

 no reason at all to go, as it does not know there is plenty of food for it 

 further up." A somewhat extensive experience of fishery literature 

 supplies me with no more striking instance of common-sense expressed 

 in simple language. 



But if the fish does not know where he would be well off, the fjord 

 fish merchants seem to have perceived that it is to their interest to help 

 him on, for we learn that since 1892 there has been carried on a system 

 of State-aided transplantation, whereby in 1895 alone more than 80,000 

 fish were transferred from the North Sea to the inner broads. A propor- 

 tion of these fish were marked by means of holes in the fins, and it is 

 by ascertaining the proportion of marked fish captured later on that 

 Petersen is able to prove, not less to the satisfaction of his readers 

 than of himself, that the inner waters are populated almost, if not 

 entirely, by transplanted fish ; while even the unmarked fish support 

 the same conclusion by bearing traces of confinement in a boat's 

 well. 



• There is an exactly parallel condition in the Mediterranean, where Professor Marion 

 has shown that the bands of young sardines, which every year enter some of the shallow 

 lagoons near the mouths of the Rhone, neither return to the sea nor survive to reproduce 

 their species wilhin the inland waters. 



