[53] POND CULTURE. 519 



it slioiiUl be iillcd in autuiun. Tf it takes a long- time to fill a pond, 

 wliicli is the case with huge pouds, especially those whose snpply of 

 water is scanty, and still more with sky ponds, which are entirely de- 

 pendent on rain and snow water, it will become imperative to till the 

 pond soon after the autumn fisheries. The necessity for filling a pond 

 in antnmn, which might have been allowed to lie dry during winter, 

 may sometimes arise from the circumstance that the water is needed 

 for other purposes besides the fisheries, e. g., to drive mills or to form a 

 supply in case of fire. The time for filling a i)ond will, of course, also 

 depend on the quantity of water which can be disposed of. 



If none of the above-mentioned circumstances render it advisable to 

 fill the pond in autumn it will, as a general rule, be well to let it lie dry 

 during winter, and not fill it till spring. Thereby it will become possible 

 to make necessary improvements in the pond, to repair the dikes, clean 

 the ditches, level rough places on the bottom of the pond, remove inju- 

 rious plants and superfluous mud, and to hoe the bottom, so as to ex- 

 pose all its parts to the influences of the atmosi^here, w hich makes it 

 healthier for the fish and better calculated to produce worms, other 

 fish-food, and useful aquatic plants. Young fry of fish of prey found in 

 the spawning and raising ponds may be destroyed, the number of frogs 

 may be diminished, &c. It will be seen that the advantages connected 

 with letting a pond lie dry during winter are so great that no pond 

 which is not to be stocked with fish in autumn, nor a pond whose sup- 

 ply of water allows it to be filled at any time, or which can easily be 

 filled in spring before it is stocked with fish, should be filled in autumn. 

 This is all the more necessary if the pond has been stocked for two or 

 more consecutive years, as owing to the lack of atmospheric influences 

 the bottom will cease to yield the necessary supi)ly of fish-food. This 

 will make itself particularly felt in those pouds which have to produce 

 their own supi)ly offish-food; and less in those ponds which receive much 

 ! water from cultivated fields and meadows, or are entirely dependent on 

 , this mode of supply ; as, for example, the sky pouds. On the other hand, 

 ' such ponds are more liable to accumulate an excessive and injurious quan- 

 tity of mud. 

 ' As regards those ponds which remain filled for two years, Teichmann 

 says that his experience has taught him that it will be advantageous 

 I not to give them their full supply of water during the first year. He 

 > states that during summer one entire side of these ponds was used as pas- 

 i ture close to the water's edge. On these dry places the cattle deposited 

 I their excrements, and it was certainly beneficial for the fish to expose 

 • these places to the fresh air during an entire summer. After more water 

 , was let into the pond in the second year, the fish undoubtedly found an 

 i abundant supply' of food in those places which had remained dry dur- 

 I ing the })receding year. This experience appears to make it desirable, 

 ( under certain circumstances, especially in large ponds which remain 

 ji filled for more than one year, which are shallow and have no high banks, 



