726 BUIvLETIN OF THE BUREAU OF FISHERIES. 



BARRICADES AND TRAPS TO INTERCEPT SPAWNING RUNS. 



That successful work at the salmon stations depends largely upon stable 

 and suitable barricades, or racks, as they are more commonly called, may be 

 instanced by the results of the work at Battle Creek, Cal., in 1903 and 1904. 

 At the height of the season in 1903 a freshet carried away several sections 

 of the rack grating, permitting the fish to escape upstream." As a consequence 

 only about 27,000,000 eggs were secured. The following season no flood occurred 

 at Battle Creek until near the end of the spawning season, and the collections 

 that year numbered over 57,000,000 eggs. 



As all of the streams are subject to freshets, the water in some instances 

 rising over 20 feet, the racks must be firmly built, and their successful operation 

 depends not only upon ingenuity in construction but the care that is taken to 

 guard against their becoming clogged with leaves and other debris in times of 

 flood — work which at times is exceedingly hazardous. Methods in the construc- 

 tion of racks vary with local conditions, as do also the methods of capturing the 

 salmon thus intercepted. 



At the Mill Creek station, in lieu of a main or upper rack, the Bureau is able 

 to take advantage of a mill dam 1 2 feet high, which effectively stops the passage 

 of salmon. Half a mile below this dam a retaining rack with the usual traps 

 prevents the fish from dropping down stream. Seining and spawning operations 

 are conducted on the streams between the dam and the retaining rack. 



At Baird, Cal. — At the Baird station on the McCloud River in California 

 are two racks or barriers between which is formed a pool 400 feet in length. The 

 upper rack intercepts the further passage of salmon, and the lower or retaining 

 rack gives the fish free entrance to the pool, but effectually prevents their return. 

 The upper rack reaches across the river, a distance of 250 feet, and is primarily 

 supported by 10 concrete piers averaging 8 feet in height and extending 5 feet 

 above low-water mark. The piers are properly fastened to the bed rock of the 

 river bottom by means of heavy iron bolts. They have a flat top 4 feet wide 

 and 6 feet long, and from top to bottom is a beveled nose extending upstream 

 at an angle of 60 degrees, making them 4 feet wide and 10 feet long at the bottom. 

 On either bank a small crib pier filled with rock supports the shore ends of two 

 10 by 10 inch stringers laid parallel from shore to shore across the tops of the 

 piers. A 2 -foot walk is built between the stringers and the whole is securely 

 wired to eyebolts built in the pier tops. 



Across the river bottom, against the nose of the piers, is a lo-inch sill. At 

 intervals of 3 feet poles 4 inches in diameter extend at an angle of 60° from the 



sill at the bottom to the stringer at the top, and are securely fastened to the 



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o At Battle Creek the low-water mark is lo feet below the top of the stringers on the rack, and 

 during a recent flood the water was 12 feet above the top, making a 22-foot rise. 



