3 '(6 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



lu the autumn of 1873 I took from my ditch 15,000 trout about the 

 leugth of a man's finger, some even as long as a hand. In 1874, how- 

 ever, the number of trout decreased, and this decrease continued until 

 1 was on the point of ceasing to place young trout in the ditch. In 

 spite of placing in it a large number of trout, I finally did not take 

 more than a few hundred from it in autumn. I also found that the in- 

 crease of the enemies of fish kept step with the increase of the fish. 

 Kingfishers, which formerly had appeared only occasionally, soon came 

 in great numbers, and of course did great damage to the trout in the 

 open ditches. I managed, however, to keep them under proper con- 

 trol by following the advice of Max von dem Borne, aud placing along 

 the ditches a large number of the excellent kingfisher traps manu- 

 factured by Adolph Pieper, in Moers. At present, numerous kingfisher 

 traps are placed along all my trout brooks and ponds, and a kingfisher 

 which comes in this neighborhood is sure to be caught within a few 

 days. In spite of this, the raising of young trout seemed to languish. 

 Occasioually the results were somewhat more favorable, but I never 

 again reached even approximately the large numbers of the first years. 



Three years ago I ascertained that a large number of shrew-mice 

 ( Wasserspitzmiinsen) had found their way into my brooks. For a long 

 time all my eti'orts to master these little animals, which are well-known 

 enemies of the eggs and young of fish, proved in vain, as 1 did not suc- 

 ceed in finding a suitable trap for catching these mice. One of my Al- 

 satian neighbors, to whom I confided my trouble, advised me to try a 

 very simple wire-spring trap, which he had successfully used for catch- 

 ing common mice. The first attempt made last year proved success- 

 ful, and this year I procured two hundred such traps, which I distrib- 

 uted along my brooks and ditches. The result was perfectly surprising. 

 Since April 1, 1884, therefore, in five weeks' time, I have caught with 

 these traps 8G shrew-mice and 8 water-rats. The traji closely resem- 

 bles Pieper's kingfisher trap, only it is constructed in a much lighter 

 manner, and does not have the little board in the center on which the 

 kingfisher alights. Above the spring there is a small contrivance 

 to which bait can be attached. For bait I use a small piece of fish. 

 These traps are manufactured by Schmerber Brothers, of Mulhauseu, in 

 Alsace, and cost only 25 marks [$G] per hundred. In every one of the 

 shrew-mice which I dissected I found a considerable quantity of indi- 

 gested and half-digested young trout — in some as many as 10. ]S'o 

 further jiroof is needed to show that a number of these mice is sulBcieut 

 to depopulate a well-stocked brook in a comparatively short time. 



I believe that now I am master of the situation, for during the last 

 few months shrew-mice have been caught only occasionally. My brooks 

 at present again swarm with young, strong trout, and it remains to be 

 sem whether some new enemy will make its appearance and prevent too 

 great a production of fish within a narrow space. 



HuNiNGEN, Alsace, Geemany, 1884. 



