WCT Multi-state Assessment February 10, 2003 



Ranked Risks to Conservation Populations 



We rated risks to 539 of the 563 designated WCT conservation populations by miles of habitat 

 occupied (Table 16 and Figure 9) and by number of populations (Table 16 and Figure 10). No 

 risk assessment was done for 24 populations located within some lands administered by one 

 tribal council in Montana. The two distinct types of conservation populations, "isolets"" and 

 "metapopulations", were segregated in the analyses. In general, more isolet populations were at 

 higher risk due to temporal variability, population size, and isolation than metapopulations, 

 especially when rated by number of populations (Table 16). but more isolet populations were at 

 less risk than metapopulations due to genetic introgression, disease, and population 

 demographics. This is indicative of the fact that while smaller, isolated populations are usually 

 much more susceptible to population level risks due to isolation, small population size, and 

 temporal variability; their isolation makes them less susceptible to genetic introgression and 

 disease risks. Conversely, while more metapopulations (large, connected populations) were less 

 vulnerable to population risks such as temporal variability, isolation, and small population 

 size, their connectedness made them more susceptible to genetic introgression and disease risks 

 (Table 16). Composite population risk scores ranged from a low of 4 to a high of 16 with most 

 scores being over 10 for isolet populations and under 9.5 for metapopulations (Figure 1 1). 

 "Isolets" are at relatively high risk from population-type risks, but at much lower risk from 

 genetic and disease risks than "metapopulations". 



Restoration Activities Implemented for Conservation Populations 



Restoration, conservation, and management activities that have been implemented to conserve 

 designated conservation populations were evaluated for the 539 conservation populations for 

 which risk assessments had been completed (Table 1 7). Angling and land management 

 restrictions have been implemented in waters and adjacent lands that affect over half of the 

 designated conservation populations. Angling restrictions often consisted of "catch and release" 

 fishing for WCT, but other restrictions such as bag and size limits and gear restrictions were also 

 included. Restoration activities, such as culvert replacement, channel restoration, bank 

 stabilization, riparian fencing, have occurred for 5 to 10% of the conservation populations. Ten 

 percent of the conservation populations are, either partly or wholly, within protected lands 

 (wilderness, national parks, etc.). 



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