ARTIFICIAL, PROPAGATION OF PACIFIC SALMONS. 



11 



at the California stations on tributaries of the Sacramento and 

 Klamath Kivers. In addition, the private hatcheries operated by 

 the salmon-cannery interests of Alaska, known as Fortmann, Kar- 

 luk. Quadra, Hetta, and Klawak, which have been hatching blue- 

 back salmon for years, collected in 1916 over 87,000,000 eggs. The 

 normal capacity of these five establishments is 197,000,000 eggs per 

 annum. The Bureau's two hatcheries in Alaska have each a capacity 

 of 72,000,000 eggs. 



CONSTRUCTION OF RACKS. 



The eggs found in salmon that are captured for commercial pur- 

 poses are in a green state, and, therefore, in all hatchery operations 

 of impoi-tance it has been found necessary to provide for the egg 

 supply by installing requisite devices for the capture and retention 



Fio. 1. — Thrpe-legged rack horse or trestle: .1.. horse head; B.B., horse legs; C.G.C., 



12-lneh hoards ti> make sides of crlli and also to act as braces; n.Ii.l)., leg hraees 



which also support bottom of crib ; E.E.E., bottom of crib ; X.X., bracket for support- 

 ing walk. 



of the brood fish. Such fishing is conducted at or near the spawn- 

 ing grounds. 



The site sek'cted for the placing of the racks should be in a good 

 spawning locality. The upper rack is placed at the head of a riffle, 

 and the stop or lower rack is installed just below a deep pool, the 

 distance between the two depending upon topographical conditions. 

 There is thus provided between the upper and lower racks a proper 

 spa\yning and fishing area, with a deep pool for a resting place for 

 tlie immature fish. In this inclosure the fish are hold until removed 

 for stripping. The racks are designed to control the movements of 

 the fish regardless of the water stages, as failure to do so means the 

 loss of a season's take of eggs. 



The usual form of rack constructed in the rivers of Washington 

 and Oregon and in most of the streams in California is built on 

 trestles or three-legged horses, their sizes depending upon the char- 

 acter of the streams to be closed, and their length upon the depth 

 of water and the angle or slf)pe to be given the rack. The legs are 

 made of pile timber from 8 to 12 inches in diameter. The upper leg 



