CENSUS METHOD 



The aim of the census was to gather sufficient information from each 

 of the -units of the fishery to calculate a rate of catch-per-unit-effort 

 smd an accurate estimate of the total catch of black-spotted trout from 

 Yellowstone Lake and River. The data gathered from each fishing party 

 contacted by Fish and Wildlife Service personnel consisted of the number 

 of anglers in the party, the area of fishing, the total hours of actual 

 fishing for all anglers, and the total number of fish taken. With this 

 information, the average effort (number of hours spent by each person in 

 fishing), and the catch-per-unit-effort (number of fish taken in one hour 

 of fishing) could be calculated. Thus, with data concerning the total 

 number of persons fishing, the above rates could be applied and a reason- 

 able estimate of the fishing mortality or total catch could be madeo 



By a systematic plan of sampling, the above data were collected from 

 each of the separate units of the fishery. In 1950, the data were grouped 

 by two-week periods so that natural changes in fishing success with pro- 

 gress of the season could be evaluated. In 19^1, however, the data were 

 collected by 2-week (biweekly) periods following the schedule shown in 

 table 1. 



Table 1 



Creel census schedule used during 19^1 season. The first day of 

 creel census was May 30, the opening day of the fishing season 

 in Yellowstone Park. 



Days in biweekly period 



Fishery Unit 12 3 



Fishing Bridge Dock X 

 Fishing Bridge X 



Complete River X 



Complete Shoreline 

 Incomplete River 



and Shoreline 

 West Thumb Dock* X XXX 



■»lVest Thumb dock was censused by Fish and Wildlife Service personnel 

 stationed at Arnica Creek field camp. 



