The 1950 estimate of catch by larger private boats moored at Lake 

 Dockj Fishing Bridge, and V/est Thumb is based mainly on a record of the 

 fishing done by one of approximately 15 boats of this type on the lake. 

 This boat reported having caught 1,205 fish from June 3 through 

 September h* As this is known to be one of the more active private 

 boats, it might be assumed that each of the 15 boats took about 300 fish 

 during the 19^0 season. This would furnish an estimate of lijJOO fish 

 for the seasone 



Since it was realized that there was a lack of accuracy of the 19$0 

 estimate, in 19^1 boat owners were contacted and two of the largest and 

 most active boats with resident boat operators kept accurate records of 

 their seasonal catches. The Lake Dock manager, realizing the importance 

 of getting the private boat catch, kept an accurate record of the 

 catches of all other private boats moored at this dockc For the three 

 active inboard boats at Fishing Bridge and the two at West Thumbs the 

 same assumption for 19^0 of 300 fish per boat has been made for the 

 1951 estimateo These data provide an estimate for the season as follows 2 



Source Catch 



Private boat records (two boats) 2^1i70 



Dock manager record (four boats) 1,082 



Estimate (three boats at Fishing Bridge Dock) 900 



Estimate (two boats at West Thumb dock) 60O 



^7052 



Combined with the estimate for the private trailer boats for the 

 two seasons, the total catch estimates for the private boat fishery on 

 Yellowstone Lake would amount to 511*877 for 1950 and 59,909 for 1951o 

 Unfortunately, in deriving the estimates as they were„ there is no mea- 

 sure of the rates of effort or catch-per-unit-effort upon which to 

 judge the change in relative condition of irhis unit of the fishery. 



YELLiaWSTQNE RIVER 



Because tagging experiments have indicated that trout move freely 

 from the lake into the river, and vice versa, it has been assumed that 

 the fish taken from the river above Yellowstone Falls^ a natural barrier, 

 are of the same population as those fish taken from the lake. During 

 the 1951 season, the river fishery was censused in the same manner as 

 the lake shore, that is, by four complete and four incomplete censuses 

 during each two-week period. Using the same formulae as for the lake 

 shore estimates of total hours, fishermen and catch were made fcr the 

 river fishery for the 1951 season (table 17) e 



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