208 U. S. BUEEAU OF FISHERIES. 



remain undisturbed until the curvature of the tail is visible to the unaided eye. 

 The accumulation of a moderate coating of sediment which readily washes off is not 

 injurious. In a few instances it has become necessary to handle the eggs during the 

 tender stage to arrest the spread of fungus, but wlicre the water supply is reasonably 

 well adapted to fish-cultural purposes such a course is rarely if ever necessary. 



REMOVAL OF DEAD EGGS BY THE USE OF SALT SOLUTION. 



Among the most noteworthy advances in the fish-cultiiral methods during the last 

 few years has been the use of salt as an aid in the removal of dead eggs. The develop- 

 ment of this process has extended over a period of several years, but it is more during 

 the last year or so through the efforts of L E. Baldridge, of the Yes Bay station, that it 

 has reached a high degree of efficiency. 



Compared with the time-honored process of picking by hand, there are marked 

 advantages in using the salt solution, and chief among these is the great saving of labor. 

 It is estimated that if the eggs happen to be of not more than mediocre quality it 

 would take at least 20 pickers to remove as many dead eggs as could two men using the 

 salt solution. Moreover, the operation is much more thoroughly performed in the 

 latter process than is possible in picking by hand. 



Another advantage of using the solution is that it is possible thoroughly to clean 

 the eggs. This greatly reduces any loss through contamination and infection resulting 

 from the decomposition and fungous growths which inevitably follow the long-con- 

 tinued presence of dead eggs that in the hand-picking method frequently escape 

 attention. Even when utmost care is taken to pick out all dead eggs, fungoused 

 masses will occasionally appear. This condition is rarely observed when the salt 

 solution has been used, and it undoubtedly means that in the aggregate many eggs 

 are saved. Still another point in favor of the solution, it is generally believed, is that 

 it acts as a tonic or stimulant to the good eggs while at the same time as a deterrent to 

 the growth of fungus. Again, in picking by hand there is apt to be loss by move- 

 ment of the eggs during delicate stages of development; and the oft-repeated insertion 

 of egg tweezers, which are bound to touch other eggs, undoubtedly at times results 

 in injury. 



Recent experience has demonstrated that the solution may be applied effectively 

 to eggs freshly taken as well as those in more advanced stages of development. 



The principle of the salt bath is simply that the specific gravity of the good eggs is 

 greater than that of the bad eggs, hence upon being placed in the salt solution the 

 g(jod eggs sink and the bad remain afloat and are easily removed. It is vitally essen- 

 tial to the success of the undertaking that the solution be of the proper strength, and 

 it is for this reason that the beginner is apt to become discouraged. If the solution is 

 too weak all the eggs, both good and bad, will sink, while if it is too strong all will 

 remain afloat. The margin of the proper density is so narrow that in the operation it 

 is necessary every few minutes to strengthen the solution by adding more salt or brine, 

 otherwise the small amount of fresh water which adheres to a basket of eggs as it is 

 lifted from the hatching trough into the solution will affect unfavorably the results 

 when treating succeeding baskets. Experience and careful observation, however, 

 will soon make it possiljle for the operator accurately to judge when to add a ])it of the 

 stock solution. It is a convenience, of course, to have a salinometer at hand when 

 preparing the solution. It is commonly the practice as an aid in preparing the solution 

 to test it occasionally with a few eggs. 



Highly successful results in using the solution with red salmoii eggs have been 

 attained at the Yes I Jay station, and a detailed description is accordingly given of the 

 methcxls pursued at that place. 



The chief it(!m of equipment consists of a water-tight wooden tank 4 feet long, 2| feet 

 wide, and 10 inches deep for holding the solution in wliich the eggs are immersed. 

 Before each basket is immersed it is necessary that the surface of the solution be 

 perfectly quiet, for any ripple or current will tend to disturb the buoyant effect of the 

 solution upon the eggs. Iherefore it was found of great convenience last winter to 

 use a floating frame made of half-inch material G inches wide fastened together verti- 

 cally and at right angles, thus forming open squares aliout 6 inches either way. After 

 each basket of eggs is lifted from the salt hath this frame is placed in the solution to 

 stop all motion of the water, ludng pushed down until it is almost submerged and held 

 firmly against the side of the tank for a few seconds. Ipon being carefully withdrawn 

 the solution is quiet and the next basket of eggs may be immersed without further 

 delay. 



Another piece of equipment is a feather fan with which gently to push the floating 

 dead eggs away from over the sul^merged basket into whicli tiie good eggs have settled. 

 Unless the dead eggs are quickly moved they too will sink. A feather fan made by 



