The importance of "natural pastures" finds expression even with the fishing laws of 

 the different countries. The laws permit catching of trout broodstock even during closed 

 seasons. Most trout breeders, for like reasons, rightly try to lease valuable neighboring 

 trout brooks in order to use them for the rearing of their broodstock. 



One or two months before the spawning period, the breeder begins with a reduction in 

 feeding . It is best stopped altogether when the spawners begin to go upstream to reach 

 their spawning grounds. In this way, any injuries to either roe or milt of the fish will 

 be avoided. 



I will mention, though, that trout never stop eating altogether, "nils is proven by 

 the presence of feces during the stripping process. 



With the beginning of full maturity, the special demands for existence on the part of 

 brook and river dwellers come to the fore, so to speak. The most perfect eggs and the 

 most prolonged movements of the spermatozoids are observed in waters with a strong cuiTent 

 ( Scheuring ). For this reason it is to be recommended to get the broodstock out of the 

 larger ponds and transfer the fish into such waters. Where broodstock is kept in natural 

 waters (brooks), it is best fished out already during the summer months and brought into 

 special ponds. The females, especially, should not be fished out too late. 



At least once every eight days, the stock ponds or tanks are gone over with a small 

 drag net and the trout are examined as to their full maturity. This has been reached 

 when the milt and eggs exude upon a slight pressure and the eggs are felt loose and 

 moveable in the female. Milt which only exudes upon hard pressure or is mixed or colored 

 with blood is still immature. It is over-ripe, when a watery fluid precedes the issuance 

 of milt and the milt itself is thin and watery. 



If not resorted to already, the different sexes are now best separated and brwight 

 into separate ponds or tanks. Keeping trout in tanks has no disadvantages as Scheuring 

 (1928) has proven again through milt tests. 



Males of the rainbow trout are easily distinguished frcm the females through a 

 vividly red stripe upon their gides. Their belly is usually somewhat darker than the 

 belly of the female and the lower jaw, in older males show a typical hook form. One also 

 notices upon them so-called "spawn rinds", i.e., a thickening of the upper layers of the 

 skin along the fins, especially around the tail fin. The females are easily recognized, 

 and at an early date, by their embonpoint and the somewhat protruding red "vulva". 



The males will attend to their reproductive functions repeatedly during one spawiiing 

 period. This especially the case when the males are kept in ponds (or tanks) whose water 

 is the overflow from tanks, plentifully stocked with females. 



As a rule, males can be stripped from 3 to 8 times at intervals of from 8 to lA 

 days, with a rest period of at least 70 "day degrees" (4 hours) between two strlppings. 

 It takes that long for spermatozoids to ripen. As a rule, repeated stripping stimulates 

 the development of spermatozoids. Scheuring was able to obtain from one male an amomt 

 of milt equivalent to 8.89 percent of its body weight. For these reasons the number of 

 males ought to be only l/zV to 1/3 of the number of females. In order not to exhaust the 

 males, many fishbreeders see to it that their ponds are not at a lower level than the 

 ponds of the females, nor do they Jceep them together with the females. But in case of 

 ijmnaturity of the males it is recommended to bring them together with the females. 



The full maturity of the female is of short duration . Aa a rule, it lasts not more 

 than 8 days , Mature eggs, carried for more than 8 days in the belly of the female show 

 signs of overripeness (degeneration). Mrsic found another disadvantage with regard to 

 overripe eggs (although still incuba table) inasmuch as such eggs will produce a progeny 

 of 86 percent of males as against a progeny of only 50 percent males under normal condi- 

 tions. And the same may be said with regard to inmature eggs (proven for frogs by Hertwig), 

 If the brood is to be later placed in natural waters or to be raised into spawners, that 

 kind of material (overripe eggs) would cause a highly disadvantageous shifting of the sex 

 ratio. Also, the number of malformations and of freaks increases with overripeness of 

 deposited eggs. 



100 



