PROPAGATION AND PROTECTION OF THE RHINE SALMON. 



By P. P. C. HOEK, Ph. D., 

 Scientific Fisliery Adviser to ilie Dutch Government. 



ENVIRONMENTAL CONDITIONS AND NATURAL HISTORY. 



Wherever it is found the salmon is highly esteemed — to the most precious 

 kinds of salmon that of the Rhine unquestionably belongs. 



"Old Father Rhine," with his very important tributaries, flows through a 

 very densely populated part of west Europe — at the same time one of the most 

 industrious and cultivated regions of the whole world. The river itself, as you 

 all know, comes from Switzerland, forms the frontier between that country and 

 the Grand Duchy of Baden, passes through a great part of western Germany, 

 then enters Holland, and in that country, with numerous outflows, finds its way 

 to the North Sea. Of the numerous affluents, which together drain a surface 

 of several thousands of square miles, some belong to Switzerland, many belong 

 to Germany, a few to the Low Countries (the Netherlands) nearer the mouth 

 of the river. 



It is impossible to treat of the propagation of the salmon of the Rhine 

 without emphasizing the important role the affluents play in the economy of 

 this fish. As a rule the Rhine salmon does not propagate on the main river 

 itself, but for that purpose enters one of the tributaries, there to spawn in the 

 upper courses or in the mountainous rivulets and brooks which are in open 

 communication with these upper waters. The main river itself plays only a 

 secondary part, so to say, in the natural history of our fish; it forms the commu- 

 nication, the open highway, between the sea and the very extensive region where 

 the natural propagation takes place. It is now a well-established fact that the 

 greater part of the young salmon hatched in the higher parts of the affluents of 

 the Rhine remain there about a year, living in that time the life of trout, and as 

 i-year-old fish, in springtime, migrate to the sea. They reach the mouth of the 

 river on their way to the ocean in the month of May, their length being then 

 from 12 to 1 7 centimeters. Most of these young salmon at that time have 

 already, or at least partly, changed their trout livery (the "parr" costume), with 



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