It is interesting to note that the success of angling from Fishing 

 Bridge is very closely associated with the movements of fish both to smd 

 from the lake by way of the Yellowstone River. This movement has been 

 recognized by tagging studies in the river and the lake* As the bridge 

 is closed to fishing until July 1 of each year, a very early or very late 

 migration of fish under the bridge would most certainly show in the results 

 of the census. This run of fish is usually at its peak in Jiilyi thus, if 

 the run were two or three weeks early due to a mild winter with early 

 melting of snows and warming of the water^ the success of angling from 

 the bridge would be considerably reduced* The migration of fish is quite 

 clearly reflected in the catch-per -unit-effort plot for 2-week periods in 

 1951 (fig. 9)0 This shows the rate to be hi^est in July, followed by a 

 rapid decrease to the middle of August where it remains relatively con- 

 stant for the remainder of the season. Moving the plot to a position 

 three weeks earlier, one can visualize the decrease in success of fishing 

 from the bridges 



LAKE SHCRE CENSUS 



This unit of the fishery consisted of approximately thirty rrilles of 

 shoreline adjacent to the highway between West Thumb and a point six 

 miles east of Fishing Bridge (fig, 1), During the 19^0 season, the ob= 

 server traveled this distance twice every third day in making the census. 

 One-half of each census day was spent in traveling the thirty miles in 

 one direction and the other half in returning over the same route. During 

 this time he contacted all available anglers along the shoreline. For 

 making comparisons with other stations, these data were also grouped into 

 2-week periods. 



Because of the fact the 1950 census method did not provide for a com- 

 plete coverage of the lakeshore unit, it was fundamental that a more re- 

 fined and efficient method of making the shoreline census be developed. 

 With the aid of a statistical analyst, a new method of census was planned 

 for the 1951 season. The 1950 data were revised in the light of the 1951 

 findings. The new method showed that 20 percent of shore anglers were 

 contacted in 1950, in contrast to 50 percent previously assumed. 



The new method was based on what are termed complete and incomplete 

 censuses, each of which was conducted four times during each 2-week 

 period, A complete census required the observer to remain at one loca- 

 tion during the entire day and to record the time of arrival and depar- 

 ture of each fisherman in a defined area. The time of the catch of each 

 fish by each fisherman was also recorded. Thus, a pattern of fishing 

 effort by hours, catch by hours, effort per fisherman, and catch per 

 fisherman was obtained. Four such locations were chosen for complete 

 censuses which represented different degrees of fishing pressure along 

 the lake shore, the average of which was assumed to be representative of 

 fishing conditions along the entire shore fishing area. Due to changes 

 in fishing pressure over the season, it was necessary to adjust the com- 

 plete census areas in order to maintain the average condition desired 

 from the complete censuses, 



19 



