1112 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [12] 



gravel, so as to prevent, as much as possible, fish and other injurious an- 

 imals from entering- the pond. Even sky-ponds are allowed to'lie dry 

 during winter, in order to destroy frogs, small crustaceans, insects, &c., 

 and are only filled a short time before they are stocked. When a pond 

 is known to contain much vermin, it is advisable to cover the bottom in 

 autumn, after the fisheries have come to a close, with coarsely-grained 

 lime. This will kill all vermin, and after the lime has been slacked, it 

 is of course not injurious to the fish. To lay the pond dry during win- 

 ter has also this advantage, that the soil by freezing becomes loose aud 

 loses its acidity. The pond should, therefore, be crossed hj one, or, if 

 the pond is large, several ditches, one meter deep. The depth of the 

 pond should be from 20 to 30 centimeters, and the edges should be very 

 shallow, with a thick growth of Glyceriafluitans, on whose floating leaves 

 the carp like to deposit their spawn. As heat is one of the principal 

 conditions for spawning and for the development of the young fish, the 

 spawning-pond should be in a sheltered location, and entirely exposed 

 to the sun, so that it can quickly be heated through. It is necessary 

 that the pond should be protected against wind, so as to prevent tha 

 formation of waves which would kill the spawn deposited on the shal- 

 low shores. The depth of water should be as even as possible during 

 the spawning-season, as its lowering would lay tbe eggs dry and kill 

 them. Hurtful birds, such as herons, ducks, and geese, should be kept 

 away from the pond ; no cattle should be watered in it, as they would 

 either devour the spawn with the floating leaves of the Glyceriafluitans 

 or kill it by treading on it. Frogs also devour large quantities of young 

 fish. Considering the importance of the spawning-ponds for the entire 

 carp-culture, and their small size, it is advisable to surround them with a 

 close wire-fence. 



The spawning-ponds should not be stocked with spawning carp until 

 the water has reached a temperature of 15<^ to 20° C. The spawners 

 should already be selected in autumn when the fisheries are in i3rogres8. 

 During winter they are kept in a good winter-pond; in spring they 

 are examined once more, and the sexes kept separate in deep basins 

 until the spawning-ponds are ready for stocking. As with the raising 

 of any animals, so also with the carp, the selection of exceptionally good 

 spawners is of the utmost importance. Although under favorable cir- 

 cumstances good fry may also be obtained from old carp, young carp^ 

 weighing from 2 to 4 kilograms, are preferable. It is advisable to select 

 from among the fish of the same age the largest and best shaped, hav- 

 ing a small head, a broad back, and slender body. The sexes can easily 

 be distinguished during the autumn fisheries. As a general rule the 

 belly of the spawner is, especially in its lower part, broader and rounder, 

 the genital aperture appears larger and reddish, and has thicker lips,^ 

 while with the milter it forms a narrow slit. It is a great mistake to 

 press the fish for the purpose of ascertaining their sex, so much as to 

 squeeze out immature milt or spawn. Such a procedure frequently 



