The actiial filling of the dan is to be avoided, if possible, during frost or -when there 

 is a heavy precipitation. Obstructive ground rises in the pond can be removed and used as 

 ground material .for the dam and by tlds means enlarge the pond surface. The transportation 

 of the ground may be conducted over the nearly completed portion of the dam. The dam is 

 thereby coii5)ressed and the dumping is made easier. The place in ivhich the sluice is to be 

 built remains exposed at first (see figure 12). In damp weather, that part of the finished 

 dam which has not been covered by grass sods is sown with grass seeds (from the hay- loft). 

 The planting of trees or willows on the dams is unsuitable. They shade the shores and make 

 supervision difficult and lure dam-destroying rats, fish foes, and fish thieves. Hotting 

 dead roots cause holes, and the roots of wind-swayed trees bring about the loosening of a 

 dam. 



The pond floor surface in a carp pcnd should be as undisturbed as possible, especially, 

 since grassy coverings and humus layers remain. Their removal would make the pond unfertile. 

 Before the pond is filled vrith water, only excessively high grass growth should be mowed 

 off, A "fish skeleton shaped" system of ditches is laid out in the bottom, which allows a 

 con^slete and thorough drying of the pond bottom. In the foregoing example, the originiuL 

 brook is used as the main ditch. On the inside of the dam foot there is a ditch to lead to 

 the sluice, the excavated earth to be used for dam building. Lateral obli.quely branching 

 ditches must connect the deeper places of the remaining bottom surface with the main ditch, 

 so that on draining no puddles remain, and the i^ole pond runs dry and all the fish are 

 carried along by the outflowing water. In case of necessity, cavities in the pond bottom 

 are to be filled in. Boggy and other bottom spots, which are raised up, form floating 

 islands vfhen the pond is covered with water, and are covered with other soil, as they 

 cause an unfavorable productive biological action by shading and the fonaation of cellulose 

 mud (see section VIII, B). Naturally the ditches must later be restored to order after 

 each fishing out. The main fish ditch is particularly and carefully constructed in front 

 of the sliiice. It is advisable to widen the ditch slightly here and to fortify the banks 

 of the ditch close to the sluice vdth fascines, so that the bottom is to some extent 

 passaole vdthout stirring up mud during a fishing out procedure. Trout ponds are a certain 

 exception, insofar, that for hygienic reasons the best possible bottom grading and slopiixg 

 must be undertaken. Furthermore, the bottom must be as firm as possible. Fish ditches, 

 on the other hand, are spared this. 



It must again be particularly emphasized that the bottom board of the sluice must 

 form the deepest part of the ditch and in fact of the pond (see figure 11). No deepening 

 or so-called fish cavity of any kind is made in front of the sluice (see Eckstein, 1929), 

 as such an arrangement greatly aged and formerly used in large ponds only hinders fish 

 removal. In the cavity always filled with v.-ater, disease instigators and fish remain be- 

 hind to endanger the regulated management in the following year. Also a deepening of the 

 trench outside of the pond behind the sluice, the construction of a so-called sluicepit, is 

 of no use and, therefore, should be omitted. By keeping single damming boards in front of 

 the sluice, the vraiter can be retarded or controlled at will until the fish have been removedj 

 without later having a continually filled water pit remaining. In very large ponds the fi* 

 trench is strongly widened as closely as possible in IVont of the sluice. 



In the above mentioned example, it is desirable to construct a so-called by-pass ditch, 

 so that the brook water need not flow continually through the pond, and especially to pre- 

 vent a flood from flowing over and endangering the dam. The ditch may branch off of the 

 brook somewhat above the entrance of the brook into the pond; and the ditch may be so con- 

 structed as to run almost horizontally along the slope above the pond surface. A weir may 

 be erected, if necessary, in the brook where the ditch branches off, or in minor circum- 

 stances, it will suffice to close the conduit to the pond with earth, if the water flow is 

 to be partially or completely stopped. In tte vicinity of the sluice, the by-pass ditch 

 may be so constructed that it can provide holders to serve in fish removal. 



If there is danger of the fish disappearing from the pond and into the brook, then 

 the water inlet must be screened off. In the absence of a drop, several oblique grates 

 (of parallel to stream rods) should be built, one behind the other, and in such a way that 

 solid objects carried by the stream are automatically shoved up on the slanted planes of 

 the sieves (see figui-e 9). I'ree swinging suspended grates, which allovf swimming matter to 

 disappear automatically, (Krause) can at times also be advantageoxis . The simplest way is 



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