BULLETIN OF THE UNITED STATES FISH COMMISSION. 
76 
will be noted below. By making a chemical analysis of the fluid of the body cavity, 
a liquid could probably be prepared that would be entirely passive and in which the 
ova could be kept for days. This, however, is unnecessary, as a saltness of three- 
fourths of 1 per cent gives a liquid sufficiently passive for washing out bloody eggs. 
Time eggs were in salt solution. 
Percentage 
of fertil- 
ization. 
2 minutes 
99 
4 minutes _ _ _ 
100 
(5 minutes 
100 
8 minutes 
99 
15 minutes _ 
25 minutes 
97 
86 
To make artificial spawning complete . — Even the best spawn-takers can not get 
all the eggs from the fish. Often the fish is not entirely ripe; but whatever the 
condition may be many of the eggs are entangled in the folds of the ovary and 
viscera and are not spawned. Under natural conditions the ovary shrivels up and 
does not obstruct the outward passage of the eggs. The number of eggs remaining 
in the fish after the artificial spawning varies from 200 to 1,500, depending upon the 
size and condition of the fish. I have found an average of 900 eggs remaining in 
55 fishes after artificial spawning. The spawning was done by experienced men 
and could not well be improved upon. 
The average number of eggs taken from a fish in ordinary spawning is 5,000. 
This was the average during the season of 1897. By removing the remaining 900 
eggs the yield can be increased about 18 per cent. They can all be removed only 
by slitting the abdomen from the pectoral fins backward, but this allows a large 
quantity of blood to mix with them. It is possible to fertilize 85 per cent of these 
eggs in the blood, but in this case the unfertilized 15 per cent have to be picked 
out of the hatching baskets, which would.be a considerable expense if the plan 
were followed. But the blood can be removed from the eggs without any detriment 
to fertilization by washing them in normal salt solution (one ounce of common salt 
to one gallon of water). They can then be fertilized in the ordinary manner. 
This method has been used at Battle Creek hatchery since 1900 with satisfactory 
results, the loss with the “remnant” eggs being but little greater than with the 
ordinary take. By care in handling the loss need not be any greater. By such 
means the take of eggs can be increased from 10 to 20 per cent without increasing 
the cost appreciably.® 
An aid to spawn-taking .—It was found that fishes were much more easily and 
rapidly spawned after cutting the body walls across the opening of the oviduct. 
Unless the cut was made considerably in advance of the vent no perceptible amount 
of blood issued. A greater percentage of the ova were spawned than if the gasli 
had not been made, and no eggs were broken in spawning, which is an important 
point. The shells or ‘ ‘ shucks ” from eggs broken in spawning are a great nuisance in 
the hatching basket, being difficult to pick out and forming a basis for the growth 
a From his study of the physiology of the Sacramento salmon in 1902, Prof. C. W. Greene, of the University 
of Missouri, has determined the amount of salt in the ovarian fluid to he 0.94 per cent, which, therefore, is the 
density of the solution that is normal for salmon ova, and should be used in washing the blood from eggs, rather 
than 0.75 per cent as used in the experiments here noted. A solution of 0.94 per cent can be made by adding If ounces 
of pure dry salt to 1 gallon of water. 
