Table 5 shows results of comparisons between years in each major 

 area. The designation^ "Fishing Bridge Fishery Area" refers to fish 

 brought into Flshin;- Bridge Dock, Lake Do;k, or landed on the shoreline 

 within a few rniles of these docks „ Parts of Yellowstona Lake contribut- 

 ing to this fishery include those in the upper shaded area on Figure 1. 

 "West Thumb Fishery Area" refers to fish brought into West Thumb Deck or 

 landed on the western shore of West 'Riunb, The lower shaded area on 

 FigTare 1 shows the waters from which these fish were "cakan. "Combined 

 Fishery" pertains to fish taken from Fishing Bridge Fishery Area^ West 

 Thumb Fishery Area, and from other lake areas, such as South Arm, Southeast 

 Arm^ Flat tountain Arm^ the Frank Island area and the Delusion Creek area. 

 "River Fishery " applies to fish caught in Yellowstone River between Fish- 

 ing Bridge and Canyon (not shown on Figure 1) „ 



The results shown in Table 5 indicate that decreases in fish size 

 have taken place. In the Fishing Bridge Fishery Arsa^ sigrdficanx. de- 

 creases were measured from 1950 to 19^1 and from l?5l to 1952 » The 

 mean total length of these trout in 19^2 was down to 338.1 millimeters 

 (13.3 inches). The West Ihumb Fishery Area showed similar declines, al- 

 though the reduction in size from 19^0 to 1951 was not statistically sig- 

 nificanto The mean total length in 19^2 was 323.6 millimeters (12,'^ 

 inches) „ In the Combined Fishery significant declines in size were 

 measured between 1950 and 1952 catches and betvjeen 1951 and 1952 catches. 

 Mean total length for this unit in 1952 was 336.5 millimeters (13.3 inches). 



The River Fishery was sampled only in 1952,, s:> no other year's measure- 

 ments are available for comparison with the 1952 figure of 330.6 millimeters 

 (13.0 inches) . 



Table 6 summarizes comparisons between units of the fishery in 1952. 

 The Fishing Bridge Fisherj-- Area and the Combined Fishery had fish of t-he 

 greatest mean total lengths, but they were net signifl?antly greater than 

 the lengths of Yellowstone River fish. West Thumb Fisheiy Area fish were 

 significantly shorter than those of the Fishing Bridge Fishery Area and 

 the Combined Fishery^ but were not shorter than t.ne river fish. 



DISCUSSION OF CHANGES 



It appears that the most significant changes in sizes of fish have 

 taken place in the northern part of Yellowstone Lake, The data presented 

 above show that the spawning runs in Pelican Creek and Arnica Cresk had 

 smaller fish each year from 1950 to 1952^ while those of Cliipmunk Creek 

 and Grouse Creek have actually had increases in fish sizes since 1950_., 

 along with decreases. This suggests that perhaps normal fluctuations in 

 fish length have been occurring in the southern streams, while a doimward 

 trend has been takini; place since 1950 in the northern, sx-reams. 



1]. 



