CHARACTERISTICS OF SPAWNING NESTS OF COLUMBIA 



RIVER SALMON 



By Clifford J. Burner, Fishery Research Biologist 



GENERAL LIFE HISTORY 



Construction of Grand Coulee Dam across the 

 main stem of the Columbia River raised a serious 

 problem concerning the salmon that spawned in 

 the upper reaches of the river and produced an 

 important part of the west-coast catch. Grand 

 Coulee was to be a high dam, with a tailrace- 

 forebay difference of about 350 feet. Although it 

 was possible to provide reasonably safe passage 

 upstream past the dam for the adult salmon, the 

 cost would be extremely high. Of greater im- 

 portance was the probability that the salmon 

 fingerlings on their way to the sea would be killed 

 in passing down the spillway or through the tur- 

 bines. It was decided, therefore, to relocate the 

 salmon rims that spawned above the Grand Coulee 

 site in four tributary systems entering the Colum- 

 bia River below that site. The Wenatchee, En- 

 tiat, Methow, and Okanogan Rivers were selected 

 to receive the transplanted salmon. 



One of the manj' questions in connection with 

 the relocation was how many salmon should be 

 placed in each stream or section of stream to get 

 the maximum yield of spawn and frj'. To answer 

 this question, a study was made of the spawn- 

 ing habits of four species of Pacific salmon of 

 the genus Oncorhynchus. These are the chinook 

 (0. tschawytscha) , the silver (0. kisutch), the chum 

 {0. keta) , and the blueback {0. nerka) . This study 

 was concerned particularly with the type of 

 stream bottom that a given species uses for spawn- 

 ing, and the space occupied by a pair of spawning 

 fish for the nest, or redd. The study included 

 redds of salmon spawning naturally in some of the 

 lower Columbia River tributaries and redds of 

 transplanted spawners in the foster rivers. The 

 information obtained was used in planning and 

 carrying out the maintenance project (Fish and 

 Hanavan 1948) but was not published. 



At this time, in view of the program for the 

 development of the lower Columbia River tribu- 

 taries in the interest of salmon production, it 

 seems worth while to set forth the results of the 

 study so that they may be available for reference. 



All species of Pacific salmon are anadromous, 

 that is, the adults migrate from the ocean into 

 fresh-water streams to spawn. They proceed up 

 rivers, such as the Columbia, until they arrive at 

 the same tributary where they themselves began 

 life some years before. Verj' few stray to other 

 streams. The female salmon deposits her eggs 

 in a nest, or redd, which she digs in the gravel of 

 the stream or shallow lake-shore waters. In the 

 process of egg laj-ing, the fertilized ova are covered 

 with successive layers of gravel to a depth of 

 several inches. The time required for the eggs to 

 hatch depends on the temperature of the water. 

 Newly hatched fish live in the gravel of the redd 

 and gradually absorb the food in the abdominal 

 yolk sac. At the end of this period, usually in the 

 late winter or early spring, they struggle up through 

 the gravel and begin to seek food. How long the 

 young fish stay in fresh water varies considerably 

 with the species, but eventually they migrate 

 downstream to the sea, where they remain from 1 

 to 3 years and grow rapidly. When they approach 

 sexual maturity, they return to fresh water to 

 spawn and thereby complete the cycle. All 

 Pacific salmon die after spawning. 



CRITERIA OF A MATURE REDD 



At the outset of this study, it was necessary to 

 determine at which stage of development a redd 

 should be measured. Redd building may be 

 divided into three stages, prespawning, spawning, 

 and postspawning. During the prespawning stage, 

 the female salmon is green, that is, the eggs are 

 neither ripe nor loose in the ovaries. Males are 

 seldom in attendance, and are frightened away by 

 the female, who repels all intruders of either sex. 

 The female digs the redd as she turns on either 

 side, at an angle of about 45° to the current, head 

 upstream, body arched, and makes a series of 

 violent flexions with body and tail. (See fig. 1.) 

 The tail strikes the gravel occasionally and the 

 strong-boiling current created carries gravel and 



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