The mysterious case of the lost fishers

Frances Stewart, John Volpe, Jason Fisher

Researchers in the School of Environmental Studies have published on the effectiveness of species reintroduction in Biological Conservation. PhD candidate Frances Stewart (photographed above, left), Dr. John Volpe (photographed above, middle), Dr. Jason Fisher (photographed above, right) and colleagues have found that in the case of fishers – a North American weasel the size of a house cat - reintroductions may not have resulted in the expected conservation success. Conservation efforts for many endangered species focus on translocating individuals from a healthy population, to help bolster numbers in a failing population. However, Ms. Stewart and colleagues found no genetic evidence that the individuals introduced to Alberta’s Cooking Lake Moraine in the 1990s survived long enough to reproduce successfully. Rather, their research implies that fishers recolonized the Cooking Lake Area from neighbouring areas, and that the “lost fishers” from the reintroduction may indicate other things are going on. The reintroduced fishers may not have survived themselves, but rather they may have acted to attract other fishers into the area, something called “facilitated recolonisation”. These results imply that landscape fragmentation may have less of an impact on fishers than previously expected.

Conservation efforts can be costly in the case of reintroductions, and attempts to maintain habitat connectivity can be at odds with development needs in the landscape. But Ms. Stewart cautions against concluding that reintroductions aren’t effective, nor that maintaining intact habitat isn’t necessary. In the case of fishers, it’s unclear how long it takes for natural recolonisation events (it could be months, years, or even generations), and what elements of the landscape fishers need for populations to remain connected. The impacts of climate change make this even harder to predict. Ms. Stewart states, “we therefore need to hedge our bets, and make sure that we do our best to promote landscapes being connected. This will ensure we have insurance for healthy ecosystems, especially in areas with lots of development.”

Research funding was provided through InnoTech Alberta the Natural Sciences and Engineering Research Council of Canada, Royal Canadian Geographical Society, Fur Institute of Canada, Alberta Environment and Parks, The Beaver Hills Initiative, Environment and Climate Change Canada, and the Alberta Conservation Association.

For more information:

Stewart, F. E. C., Volpe, J. P., Taylor, J. S., Bowman, J., Thomas, P. J., Pybus, M. J., & Fisher, J. T. (2017). Distinguishing reintroduction from recolonization with genetic testing. Biological Conservation, 214(Supplement C), 242-249. doi:

Frances Stewart,

Author, Alina Fisher