MIDDLE THOMPSON LAKE 

 T^ke Descripfinn: 



Middle Thompson Lake is a large, relatively deq) lake. It is the middle lake in the TCL. Middle 

 Thompson Lake receives water from Upper Thompson Lake and several small tributaries and 

 flows to the Thompson River and Clark Fork River through Lower Thompson Lake. The lake 

 has a maximum dq>th of 160 feet and has a sur&ce area of 602 acres (Figure 5). Between March 

 1, 1993 and February 28, 1994, FWP estimated that as many as 5,379 anglers, of which 94 

 percait were Montana residents, fished at Middle Thompson Lake (Montana Statewide Angling 

 Pressure Report). 



T.akP ManagPmpnf Sfflfiis; 



Management of Middle Thompson Lake commenced in 1936 when 72,500 rainbow trout and 

 15,000 cutthroat trout were planted (Table 5). Between 1936 and 1992, various stocking options 

 v/erc attempted that gena:ally reflected stock availability and angler preferences with some notable 

 excq)tions. By 1953, rainbow trout, cutthroat trout 0>robably Yellowstone cutthroat trout), and 

 brook trout populations were established over renmant native westslope cutthroat and bull trout, 

 and over mountain whitefish, northern squawfish, largescale sucker, longnose sucker, and redside 

 shiner populations. 



In addition, unauthorized plants have established largemouth bass, yellow perch, and 

 pumpkinseeds in the Thompson lakes chain. Northern pike were first found in 1965 in Upper 

 Thompson Lake, and exist at relatively low levels in Middle Thompson Lake. Lake trout are 

 periodically cs^tured in the lake and are most likely the result of unauthorized plants from nearby 

 McGr^or Lake and/or migratory movemoit from McGregor Lake through McGregor Creek and 

 the Thompson River. It appears that the native gamefish populations have been effectively 

 replaced by exotic species fix)m both authorized and unauthorized introductions. 



Kokanee salmon were established in Middle Thompson Lake through a series of plants in Upper 

 Thompson, Middle Thompson, and Lower Thompson Lakes between 1951 and 1953, and again 

 in 1963. The kokanee introductions were successful in establishing a self-reproducing kokanee 

 population. Kokanee have not been planted in the lake since 1963, although it may be possible 

 that kokanee stocked in Lower Thompson Lake since 1986 may be supplementing the Middle 

 Thompson Lake population. The kokanee spawn in late October along the shoreline at depths of 

 5 to 40 feet. 



FWP has monitored kokanee populations by gillnetting during spawning runs since 1968. In that 

 time, mature kokanee have ranged in size from mean lengths of 11 inches in 1968 to 18.3 inches 

 in 1988 (Table 6). Anglers have complained about decreasing catch rates for kokanee in recent 

 years. 



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