LAWS AND PROPAGATION 43 



catch. Secondarily, this restriction served to hmit the number caught 

 by reducing the days open for fishing. At present there seems to be no 

 good reason for removal of closed seasons in the northern states dur- 

 ing the spawning seasons. In most years many more fry are produced 

 than the waters could ever support, but the older fishes adjust this by 

 eating up the surplus. This is the aquatic operation of the natural re- 

 productive principle that animals produce overabundance of offspring 

 from which nature must take a toll. The real problem is to maintain 

 a sufficient number of large adult fish to keep the offspring reduced 

 and thus prevent the survival of too many young, which would result 

 in a crowded, stunted population. Any proposed abolishment of re- 

 strictions on creel hmits and seasons should first be carefully tested on 

 a series of experimental lakes. 



In addition to protective laws, it has long been customary to utilize 

 artificial propagation as a supplementary measure in the conservation 

 of fishes. During the past seventy-five years hatcheries for the produc- 

 tion of certain game fishes have sprung up all over the United States 

 for the purpose of aiding and improving nature's methods. It seemed 

 obvious to early fishery experts that often only a small number of eggs 

 hatched under natural conditions. It was estimated that if these eggs 

 were hatched under controlled and protected conditions, a much great- 

 er number of fishes could be produced and returned to the lake. Con- 

 sequently, fishermen have felt that if their favorite lake was stocked 

 annually with fry, the problem of fish maintenance would be taken 

 care of. Stocking has become the sedative for fishery headaches. 



The eggs of only certain species can be readily propagated under 

 hatchery conditions. Members of the salmon-trout and whitefish fam- 

 ihes yield readily to hatchery manipulation. Northern pike, walleyes, 

 perch, and suckers can also be easily propagated in hatcheries. Many 

 other fishes, particularly those which build nests, do not readily ac- 

 commodate themselves to hatchery methods. 



The eggs for hatchery operations are obtained by stripping the 

 adult fishes. In some cases, as with trout, these may be brood stock 

 kept in ponds or tanks. Eggs from most other species are usually ob- 

 tained from wild stock. When the adults become sexually mature they 

 migrate to the spawning beds where traps or nets can be placed to 

 catch them. Often this is on some tributary stream. At this time their 

 bodies are gorged with eggs and sperm which will ripen in a few days. 

 The fishes are eventually relieved of their eggs and milt or sperm by 

 geijtly manipulating their distended sides. The eggs and the milt are 

 placed in a container and gentlj^ stirred. In a matter of minutes the 

 eggs are fertilized. Such eggs harden and change color, and are called 

 eyed eggs. They are then placed in running water for further develop- 

 ment. The eggs may be placed on trays in troughs of running water. 



