558 KEPORT OF COMMISSIONER OF FISH AND FISHERIES. [20] 



It is also useful to have in the hatchmg-rooins a place for tanks where, 

 during the proper season, and separated by sexes, the spawning fish 

 destined for artificial fecundation may be kept. This is done on a large 

 scale at Hiiningen, where there are great tanks in the ground con- 

 structed of concrete. It has already been said that at Berneuchen 

 every provision in this respect has been carefully made by Max von 

 dem Borne. It is not necessary to speak of the size of these tanks, as 

 they will have to be in proportion to the number of spawning fish kept 

 on hand in each establishment. 



Artificial fecundation of salmonoids. — After it has been ascertained 

 that the spawning fish have reached sexual maturity artificial fecunda- 

 tion may commence. This may be done either by one person alone or 

 with the aid of an assistant.* 



In the first case the female fish is taken from the water and held with 

 the right hand over the basin destined to receive the eggs. If the fish 

 is large it is held inclined at a sharp angle. The belly of the fish is 

 then pressed with the thumb of the left hand, the movement being in a 

 downward direction. 



If another person assists in the operation he must hold the fish by 

 the tail by means of a cloth. The two operators hold the fish almost 

 vertically over the basin, the first one holding it by the head with the 

 hand and in the manner indicated, and the second by the tail. The 

 first has to go through the manipulation described above to cause the 

 eggs to come forth. The male fish is subjected to exactly the same 

 operation. 



The amount of vn-essure should correspond with the greater or less 

 degree of maturity of the female, without, however, passing certain 

 limits, as excessive pressure would injure the fish without reaching the 

 object in view. In some cases the eggs have reached such a state of 

 maturity that they will come out of themselves when the fish is exam- 

 ined to ascertain whether the genital gland has swelled enough to be 

 operated on. 



In natural spawning the salmonoids will deposit their eggs at differ- 

 ent, more or less. short, intervals ; while where the process is artificial 

 they all come out at one and the same time with a certain violent move- 

 ment, which, however, does not interfere with their successful embryo- 

 nation. The milt of one male fish is used for the eggs of two or three 

 female fish. 



In primitive fish-culture the eggs were kept under the water to be 

 fecundated, as people believed that in doing so they followed the teach- 

 ings of nature. But it frequently happened that many eggs were not 



* The male fish may be recognized by having a more slender body, and its sexual 

 maturity by tbo brown color of the skin of the belly. When the male fish is large 

 its jaws are more booked than those of the female. The female is recognized by 

 having a stouter body ; it has reached maturity when the belly is swelled out and 

 elastic, and particularly puffed up above the anal fin, and when the reddish genital 

 gland begins to swell. 



