OCEAN DISTRIBUTION, GROWTH, AND EFFECTS OF THE TROLL 



FISHERY ON YIELD OF FALL CHINOOK SALMON 



FROM COLUMBIA RIVER HATCHERIES 



Kenneth A. Henry^ 

 ABSTRACT 



Data are presented depicting the distribution of some stocks of Columbia River hatchery 

 fall Chinook salmon in the northeast Pacific Ocean. These are based on recoveries of 

 marked fish. Also presented are the apparent growth histories for fish from the Kalama 

 and Spring Creek Hatcheries as well as a graphic population model for Columbia River 

 fall chinook salmon. Finally, the effect on total yield for varying troll fishing mortalities 

 for the 3-, 4-, and 5-year-old fish is analyzed and the results depicted in three-dimensional 

 yield diagrams. In most instances, at least at the lower levels of estimated natural mor- 

 tality, troll fishing of the younger fish reduced total yield. 



A cooperative program was undertaken between 

 the various fishery agencies in the United States 

 and Canada to estimate the contributions to var- 

 ious fisheries of fall chinook salmon (Oncorhyn- 

 chiis tshawytscha) produced by a number of Co- 

 lumbia River hatcheries. Approximately 10% of 

 the output from 12 hatcheries for the brood years 

 1961-64 was marked by the removal of certain 

 fins. The design of this experiment, including 

 a detailed account of the procedures used in cal- 

 culating the number of marked fish recovered, 

 and details of mark recoveries for the 1961 brood 

 have been reported by Worlund, Wahle, and Zim- 

 mer (1969). Details of mark recoveries for the 

 1962 and 1963 broods were given by Rose and 

 Arp (1970)' and by Arp et al. (1970', respec- 

 tively. Cleaver (1969) made a detailed analysis 



^ National Marine Fisheries Service Northwest Fish- 

 eries Center, 2725 Montlake Boulevard East, Seattle, 

 WA 98102. 



' Rose, J. H., and A. H. Arp. 1970. Contribution 

 of Columbia River hatcheries to harvest of 1962 brood 

 fall chinook salmon {Oncorhynchus tshawytscha) . Bur. 

 Commer. Fish., Columbia Fish. Program Off., Appraisal 

 Section, Portland, Oreg. 27 p. (processed). 



' Arp, A. H., J. H. Rose, and S. K. Olhausen. 1970. 

 Contribution of Columbia River hatcheries to harvest 

 of 1962 brood fall chinook salmon (Oncorhynchus tsha- 

 wytscha). U.S. Dep. Commer., Natl. Oceanic Atmos. Ad- 

 min., Natl. Mar. Fish. Serv., Columbia Fish. Program 

 Off., Portland, Oreg., Econ. Feasibility Rep. 1. 33 p. 

 (processed). 



of the 1961 brood based on mark recoveries. His 

 analysis included estimating ocean mortality 

 rates, maturity schedules, and, for the Spring 

 Creek and Kalama fish, the effect of no ocean 

 fishing on total yield. Henry (1971) made a 

 similar analysis for the 1962 brood and, wher- 

 ever possible, compared the results with those 

 obtained for the 1961 brood. The general re- 

 lease and recovery areas covered by this marking 

 program are shown in Figure 1. 



Although a total of 12 hatcheries was involved 

 in this study, fish from only two hatcheries, 

 Spring Creek and Kalama, received specific 

 identifying marks for all 4 years. Each year 

 fish from two of the other ten participating 

 hatcheries (but two different ones each year) 

 also received special identifying marks. In ad- 

 dition to specific marks for four hatcheries each 

 year, a certain proportion of the output from all 

 participating hatcheries had a common mark. 

 This mark — that is a composite of all the hatch- 

 eries — is referred to as the general mark. Thus, 

 it is possible for only Spring Creek, Kalama, and 

 general mark fish to analyze mark recoveries 

 from all four brood years. 



In the report, I have analyzed the mark re- 

 coveries for Spring Creek, Kalama River, and 

 general marked Columbia River hatchery fall 

 chinook salmon from the four consecutive brood 



Manuscript accepted January 1972. 



FISHERY BULLETIN: VOL. 70. NO. 2, 1972. 



431 



