SALMON RUNS OF THE COLUMBIA RIVER IN 1938 



115 



it to be justified here. This gives the following estimated weights: For the week 

 ending April 30, 12.20 pounds; April 23, 10.42; September 3, 25.60; September 10, 

 25.05; September 17, 24.50; September 24, 23.95; October 1, 23.40; October 8, 22.85; 

 October 15, 22.30; October 22, 21.75; October 29, 21.20; and for the week ending 

 November 5, 20.65. After this date so few fish were taken in the fishery that an 

 approximation on the basis of about 20 pounds is adequate for all purposes. 



Table 11. — Estimated weights of chinook salmon in the commercial catch in Zones 1 and 2 for the 

 spring season of 1939. Figures for the first 3 weeks were extrapolated 



In converting poundage of silver and chum salmon to numbers of fish we here 

 adopt an average weight of 10 pounds for both species — the same as that adopted for 

 steelhead trout. This is not in accord with the figures commonly given, viz, 7-9 

 pounds for silvers and 8-10 pounds for chums. Some years ago, however, the writer 

 measured and weighed several hundred silver and chum salmon taken on the lower 

 Columbia River, and these gave averages for both species that were considerably over 

 10 pounds — 240 chums averaged 10.3 pounds with a standard deviation of 2.0, and 

 133 silver salmon averaged 10.9 pounds with a standard deviation of 2.6. This average 

 does not include 16 silver salmon grilse which were in the same collections. The 

 samples came from fish caught in traps and the small grilse are seldom taken by gill 

 nets although, as stated above, this form of gear is of primary importance in the 

 Columbia River fishery. In view of these figures, and the purpose to which the esti- 

 mates are to be put, it seems reasonable to use a conversion factor of 10 pounds 

 for both of these species. 7 



Some time is required for the journey of the fish up the river, so that on a given 

 day the fish in the upper river may be expected to represent an entirely different stock 

 from that to be found simultaneously in the lower river, although it is the same stock 

 as was to be found in the lower river during an earlier period. Therefore, in order to 

 aid interpretation of some of the more important data, these have been presented so 

 that as nearly as possible those referring to the same stocks of fish are placed on the 

 same lines in the table. In other words, the several series of data have been so "lagged" 

 that comparable portions are related to the same marginal date — which date is the 

 end of the week in which the fish may reasonably be expected to have entered the 

 river from the ocean. From a careful examination of tables 1 to 5 it appears that a 

 given group of fish that entered the river and were to be found in Zones 1 and 2 in a 

 given week (the week of the marginal date in the table) would be in Zones 3 to 5 the 

 next week, at Bonneville and in Zone 6 during the second week, and at Rock Island the 

 fourth week after their appearance in Zones 1 and 2. 



In table 12 the dates given in the left-hand margin are those ending the weeks 

 during which the fish were in Zones 1 and 2, the estimated catches made in Zones 3 to 5 



' Since this report went to press a paper by Wilbert Chapman, of the Washington State Department of Fisheries, dealing with 

 the weights of Ash taken in the Columbia River fisheries has appeared. His figures are somewhat different from ours but it is not 

 possible to give a critical discussion of them here. 



