398 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



laws, of existing causes; and in treating of our relations to some other 

 useful marine animals, not mentioned so far, I shall be able to be brief. 



First, as to the herring: formerly it was thought that at certain pe- 

 riods the herring in their migrations from their home in the northern 

 seas, also visited our coasts, and that all those which escaped fish of 

 prey and the fishermen again returned to their home. Now, we know for 

 certain, that every part of the Baltic which is distinguished from other 

 parts of the Baltic by its temperature, its vegetation, and its fauna, has 

 its own peculiar kind of herrings. Thus the herrings of the bays of 

 Kiel and Eckernforde, as well as those which ascend the Schlei, belong 

 to one and the same kind, which fact leads us to the conclusion that 

 they are born and developed within the limits of this territory, and 

 that, therefore, it is a matter of considerable importance what relations 

 we hold to the conditions of life in this their home. 



The herring which, during the winter months, find good food in the 

 bays of Kiel and Eckernforde, migrate, when their sexual organs ap- 

 proach maturity, to shallow coast waters having less saltness than the 

 Baltic, especially to the upper portions of the Schlei. As they spawn 

 in these shallow brackish waters, and as the young herring are hatched 

 there, it is highly important to let at least as many full-grown and 

 sexually mature herrings get there as is necessary to keep the stock of 

 herrings in our coast waters at its average height. 



According to the reports made by the Schleswig fishermen to the 

 Kiel commission for the investigation of the German seas, the herring 

 fisheries in the inner portions of the Schlei have not declined during the 

 period 1878-1882, although during that period more nets than formerly 

 have been placed outside the mouth of the Schlei. Even the building 

 of a railroad bridge across the Schlei has not disturbed the herring in 

 their ascent. But if, by an increase of the number of stationary nets 

 outside the mouth of the Schlei, and of the nets and herring-fences in 

 the narrow parts of the Schlei, the herring fisheries in the entire coast 

 territory of Schleswig-Holstein should be caused to permanently decline, 

 the limits of the allowable fisheries would have been exceeded. Want 

 of food cannot cause a decrease of the average number of herring or 

 other useful marine animals in our coast-waters or in the sea, because 

 the plants and small animals which form the principal articles of fish- 

 food are every year produced anew, and therefore remain in the sea. 

 If, therefore, the quantity of useful marine animals is diminished by the 

 interference of man, we must find the cause of this in the destruction of 

 too large a number of spawn-producing individuals. 



In a territory of brackish water so limited and peculiar as the upper 

 Schlei the introduction of a fish of prey may also cause a change in the 

 quantity of fish. In 1S7."> a number of pike perch were placed in the 

 Schlei ; and in 1S81 fish of this kind were caught weighing 3 to 1£ kilo- 

 grams apiece. As this fish chiefly lives on small fish, any considera- 

 ble increase of its number in the Schlei will not fail to exercise an inilu- 



