558 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



also fish that are weak and gasping after air. The craw-fish perish 

 first, next the frogs, then the predaceous fish, and finally the carp, and 

 the openings are surrounded by crows. The remedies for dangers from 

 these sources are increase of the number of openings, flooding, and 

 finally immediate fishing-out of the pond. A general destruction of fish 

 may also occur in summer, if the water becomes so low in hot weather 

 that vegetable and animal matter begins to putrefy and scum becomes 

 prevalent, or also if much manure or ditch-water flows into the pond. 

 The fish, in such cases, swim along the surface, gasping after air, and 

 finally die. A heavy rain is usually the most efficient remedy, in the 

 absence of which nothing remains but copious additions of water, or 

 immediate capturing of the fish. A pond in which the fish have died in 

 this way should be drained dry and put in order. It is very important 

 not to stock the pond too full. This was considered impossible in 

 Bohemia two hundred and fifty years ago, but the evidence in recent 

 times is conclusive that not only smaller fish are obtained, but also less 

 total weight of fish, when the stock exceeds certain limits established 

 by experience. In Schleswig-Holstein it is assumed that, in a good 

 pond, one carp can be fattened per 150 square feet, but that generally 

 70 to 80 fish to about two-thirds of an acre are plenty. The carp in 

 ponds there are marketable at three years, but generally only after four 

 years. Small ponds may be stocked proportionally heavier than large 

 ones. In general, it is not advisable to stock a pond with carp of differ- 

 ent sizes. 



