SIZE, AGE, AND FECUNDITY OF THE SPAWNERS 



All of the spawned-out carcasses that could be 

 retrieved were measured. Two measurements 

 were obtained for each fish : fork length and mid- 

 eye to posterior end of the hypural plate. The 

 latter measurement exchides the snout and tail — 

 appendages that are usually distorted on spawn- 

 ing salmon. The snout becomes elongated, particu- 

 larly in the male, and the tail of the female is 

 damaged in digging the redd. 



Length-frequency curves by sex for the upper 

 Yakima River and Naches River subareas (fig. 3) 

 show that fish of both sexes are longer in the 

 Naches River subarea than in the upper Yakima 

 River subarea.- Mean lengths are 45.5 and 65.4 

 cm. for the males and 57.3 and 71 cm. for the 

 females in the respective areas. The frequency 

 distribution of length of males from the Naches 

 River subarea is trimodal with peaks at 40, 61, 

 and 79 cm. These modes correspond to those in 

 samples of spring chinook salmon that are captured 

 in the gill net fishery at the mouth of the Columbia 

 River — fish that belong to age groups 1.1, 1.2, 

 and 1.3, respectively.^ Oidy two modes — at 40 and 

 55 cm. — appear in the length-frequency curve of 

 males from the spawning area in the upper Yakima 

 River subarea. These modes are comparable to the 

 modes of the 1.1 and 1.2 age groups in the fishery. 

 Females from the Naches River subarea have a 

 single mode at 73 cm., which corresponds to the 

 mode of females of the 1.3 age group in the fishery. 

 Females from the upper Yakima River subarea 

 have a single mode at 57 cm., which corresponds 

 to the mode of the 1.2 age group in the fishery. 

 We were unable to verify these gross length-age 

 relations with scale data; the scales from spawned- 

 out fish were so deteriorated that ocean ages were 

 undeterminable. 



NUMBER OF EGGS RETAINED BY FEMALE 

 SPAWNERS 



In 1960 and 1961, 82 females were examined for 

 the number of eggs retained after spawning. 

 Results were: eggs — 47 fish; 1 to 10 eggs — 22 fish; 



' The upper Yakima River subarea, by our dennitioii, includes tliat part 

 of the Yakima River and its tributaries that lies above the confluence of the 

 Yakima and Naches Rivers; the Naches River subarea includes the Naches 

 Biver and its tributaries; and the main Yaliima River is that part of the river 

 that Ues downstream from the confluence of the Naches and Yakima Rivers. 



3 The method of designating age follows the scale formulas of Koo (1962). 

 The number of winters at sea is shown by an Arabic numeral preceded by a 

 dot; similarly, tlie number of winters that the salmon spent in fresh water 

 (not counting the winter the egg was in gravel) is shown by an Arabic numeral 

 preceding a dot. Both are shown by two Arabic numerals separated by a dot. 

 A salmon of age 1.2 spent 1 winter in fresh water and 2 winters in the ocean; 

 the fish is 3 years old and in its fom^th year of life. 



11 to 100 eggs — 10 fish; and over 100 eggs — 3 fish. 

 The nimiber of eggs retained by tlie spawning 

 females does not appear to have any great effect 

 on estimates of egg deposition. 



ESTIMATED NUMBER OF EGGS DEPOSITED 



Number of eggs deposited, Y, was estimated by 

 the formula 



i = l 



where n, is the number of redds in stream (i), and 

 Y| is the estimated mean fecundity of the female 

 spawners in stream (i). Here, in turn, Yi = 

 — 3,634-1-105.51 X, where Xi is the mean fork 

 length in cm. of female spawners in stream (i). 

 The values —3,634 and 105.5 were reported by 

 Galbreath and Ridenhour (1964), who investi- 

 gated the fork length-fecundity relation of chinook 

 salmon in the Columbia River. We used the dual 

 measurements taken on the spawning grounds to 

 convert to fork lengths the mideye to hypural 

 plate measurements. These fork lengths are sub- 

 ject to error introduced by the elongation of the 

 snout in the male and the wearing away of the 

 caudal fin rays of the female in redd building. 

 Although we were unable to measure this error, 

 we believe it to be small. 



The number of eggs deposited in the Yakima 

 River system as a whole and that of each subarea 

 declined markedly between 1957 and 1961 (table 2). 



SEAWARD MIGRATION AND SURVIVAL 

 OF PROGENY 



We designed our studies with young salmon to 

 estimate the number of fish that migrated seaward 

 each spring. To make this estimate, we trapped and 

 counted a sample of migrating fish each day during 

 the 1959-63 migrations and from these partial 

 counts made daily and seasonal estimates. 



Sampling was at Prosser, Wash., on the lower 

 Yakima River where a 3-m.-high dam creates a 

 pool from which a canal transports water to a 

 power plant 25 km. downstream. A battery of 

 electrically powered rotary screens, 1.6 km. 

 downstream from the entrance of the canal, 

 diverts fish into an underground conduit which 

 returns fish to the river. Just before it reenters the 

 river, the conduit is equipped with a trapping 

 system which, when activated, captures all fish 

 that are being returned to the river (fig. 4). An 

 aerial photograph of the area was the basis for a 



350 



U.S. PISH AND WILDLIFE SERVICE 



