PACIFIC SALMON FISHERIES. 207 



injury ■whatever from being packed together in this manner, the water being supplied 

 in a way that forces it through the eggs, partially supporting and circulating through 

 them. The meshes are too small to permit the eggs to pass through, although the fry 

 are able to do so. 

 The advantages of this apparatus and method are : 



(1) The top of the tray or basket is out of the water and always entirely dry; con- 

 sequently in handling it the hands are kept dry. 



(2) By tilting one end of the tray up or down a little or by lifting it entirely and 

 settling it gently back again in its place the bad eggs "\\"ill be forced to the top; thus a 

 feather is not required in picking over the eggs and the injuries very often inflicted 

 vdih it are avoided. 



(3) The top of the tray being above water, the eggs can never run over the top nor 

 escape in any way, which is a great advantage over the shallow form of tray. 



(4) There is economy of space: 30,000 to 40,000 eggs can be placed in each basket, 

 pro\ided a sufficient quantity of water is available. Two troughs 16 feet long and 1 

 foot wide will by this method carry about 500,000 salmon eggs. The deep trays may 

 be filled at least half full of eggs, and thus 10 times as many eggs can be hatched in 

 the same space and vriih the same supply of water as by the old method. A good but 

 gentle circulation is continually maintained through the eggs. 



(5) The deep-tray system is admirably adapted to getting rid of mud that has col- 

 lected on the eggs, for all sediment accumulating about them can be easily removed 

 by gently mo\'ing the tray up and down a few times in the water: but if the deposit of 

 mud on the troughs becomes so exce8si\e as to be unmanageable, a false bottom of 

 wire cloth or perforated zinc can be placed in the troughs at a suitable distance above 

 their real bottom, lea\'ing a space of about 1 or 1^ inches between the ^\■ire cloth and 

 the trough bottom. By this means the mud that comes into the trough -wall sift down 

 into the space below the wire cloth entirely out of the way of the lish, the movements 

 of the fish themselves helping very much to produce this result. Should the accu- 

 mulation of mud in the space below the false bottom of the trough become too great, 

 it can easily be sluiced out in various ways. 



When quinnat salmon eggs are simply to be matured for shipment, hatching trays 

 with one-fourth or one-fiftli inch square mesh will answer the purpose, but when the 

 eggs are to be hatched in them, everj'^ alternate strand of ■wire running lengthu-ise, 

 or, better still, every second and third thread, should be left out in order to form an 

 oblong mesh througli which the newly hatched fry, after separating themselves from 

 the unhatched eggs, can escape from the hatching trays into the trough below. 



At Baird eggs kept in water averaging about 54° F. hatch in 35 days. The allowance 

 of 5 days' difference in the time of liatching for each degree of change in the water 

 temperature is approximately correct. 



For the first few days the eggs of the quinnat salmon are very hardy, and at this 

 time they should be thoroughly picked over and the dead ones removed as far as 

 possible before the delicate stage during the formation of the sfjinal column comes on, 

 80 that during that critical period they may be left in perfect quiet. As soon as the 

 spinal column and the head show plainly, the eggs are hardy enough to shij), but when 

 tnere is time enough it is better to wait a day or two until the eye-spot is distinctly 

 visible, after which time the eggs will stand handling and may be safely shipped if 

 properly packed. 



HANDLING EGGS IN HATCHERY.a 



At some of the Bureau's stations where salmon eggs are handled it was the custom 

 until a few years ago to "bury " the eggs or leave them undisturbed (aside from picking 

 onc(; the day after spawning) for two or three weeks after putting them in the baskets. 

 The result was that they were in some instances literally buried under and in such a 

 mass of mud and sediment that many eggs were killed. Discontinuance of the prac- 

 tice resulted in a very appreciable impro\ement. 



When the water is so turbid as to cause a heavy deposit of sediment, it is better to 

 go over the eggs occasionally, even through the critical stages of development, or 

 until the line of the fish ia well formed. Of course the eggs must be handled with 

 utmost caution at all times, but owing to their extreme sensitiveness during the two 

 or three days following the closing of the blastopore and until a perceptil)le curve 

 shows in the tail, they should be left entirely untouched. It soon becomes easy to 

 determine the stage of an egg's development by holding it up to the light between the 

 thumb and forefinger. In the absence of cautious and skilled operatives and unless 

 the water is roily for an extended period, it is undoubtedly better to let the eggs 



a Fi.sh Culture in Alaska, by Ward T. Bower. Jn Alaska Fisheries and Furlndastries in 1911. U.S. 

 Bureau of Fisheries Document No. 760, pp. 81, h2. Washington, 1912. 



