22 tJ. S. BUREAU OF FISHERIES. 



suit in expressing some immature eggs that are incapable of more 

 than imperfect fertilization, and it is very liable to injure the 

 ovaries or other organs of the fish. The eggs in the ovaries of a 

 trout clo not all ripen at the same time. Those in the posterior end 

 mature first, and it is good practice in all cases to take only such 

 eggs as come freely from the fish by very gentle pressure, which 

 should extend very little, if at all, forward of the ventral fins. In 

 some instances it may be desirable to retain the fish for a second 

 stripping a few days later. 



Eggs taken in close proximity to a regularly established hatchery 

 may, of course, be transferred there immediately for development, 

 but when secured at distant field stations it is necessary to hold 

 them at the point of collection until they reach the eyed stage, as 

 green trout eggs are so tender that they rarely can be subjected with 

 impunity to the rough treatment incidental to a long journey. 



As a rule, an eyeing station consists of a small building equipped 

 with a number of troughs patterned after the standard hatching 

 trough described elsewhere. A gravity water supply should be 

 provided and, where it is available, spring water of a volume not 

 seriously affected by the falling temperature of late autumn is 

 selected for this partial development work, as such a supply in- 

 sures the rapid advancement of the eggs, making it possible to ship 

 them to the main hatchery before the beginning of winter. 



The troughs and equipment should be standard size. Trays 14 

 by 16 or 14 by 28 inches, as described, are satisfactory. In cases 

 where the eggs are to be incubated and the fry held in a limited space 

 until ready for planting, trays covered with wire cloth 14 to 16 

 meshes to the inch, as described on page 28, are useful. 



As manv as eight trays may be stacked in a trough compart- 

 ment, one compartment being reserved for the reception of trays 

 from the other compartments when the eggs are picked over and 

 cleaned. As the trays of eggs are picked over one by one they are 

 transferred to the empty space in the trough, and each compartment 

 emptied becomes in turn the depositing place for another stack 

 of trays until all occupy new space. Four small blocks one-half 

 inch in thickness are tacked to the rough bottom in the corners of 

 each compartment on which the trays rest, thus permitting a flow of 

 water underneath. 



Wlien the eggs are brought in from the stripping place, they are 

 measured in a tin cup or glass graduate, the capacity of which has 

 been established by count, and are then placed on the trays. As each 

 tray is filled it is gently settled in place in one of the compartments. 

 When there is an ample amount of water, as great a quantity is 

 admitted into each trough as will flow through the eggs without dis- 

 turbing them, but in case of a limited supply the eggs may be carried 

 to the eyed stage in good condition with a flow of not over 2| gallons 

 per minute to a trough of 200,000. 



During the earlv stages of incubation the eggs should be handled 

 as little as possible, but in order to prevent the development of 

 fungus it will be necessary to pick them over at intervals, removmg 

 all white eggs and those that are known to be dead. The lengths of 

 these intervals can be determined only by close observation, as the 

 necessity for frequent picking will be governed largely by the vary- 



