|
Inventory of Fisher Populations
and Reproductive Dens
in the Bridge River Watershed 2011
|
2011
|
Flooding of the Bridge River Valley by the Carpenter and Downton reservoirs likely removed many of the large, cavity-bearing trees that fishers (Martes pennanti) may have used for reproductive dens. This affected the supply of critical denning structures and the sustainability of fisher populations in this watershed. To assess and potentially mitigate the footprint impacts of these reservoirs on fishers and their reproductive habitat, baseline information on the fisher population and the abundance and distribution of cavity-bearing trees is needed. We conducted winter track count transects in 48-20 kmē grid cells spread throughout the assessment area to determine if fishers are sufficiently widespread to warrant future habitat restoration efforts.
We conducted 1415 km-days of track transects in the Gun, Tyaughton, and Yalakom watersheds over 4 survey sessions between December 2010 and March 2011. We encountered 72 fisher, 92 American marten (Martes americana), and 14 wolverine (Gulo gulo) tracks along 680 km of transects. Fishers were well distributed across the assessment area, with detections in 50% of the cells surveyed. Fisher tracks were generally more frequent along riparian areas in lower elevation Interior Douglas-fir habitats and in southern portions of the assessment area above Carpenter Lake. Fishers may be more common in these areas because shallower snow depths lower the cost of locomotion and large diameter cottonwood in riparian areas provide potential reproductive denning habitat. Based on the cell size used for this study, we estimate that 10 - 20 fishers may occur within the assessment area, which is in the range of other fisher populations studied in BC. These results suggest that the density of fishers is sufficiently high to warrant further population and habitat inventory. We recommend that a more rigorous mark-recapture inventory of fishers be conducted during winter 2011-12, which will build on the solid foundation that was achieve ...
|
wsi_4989_rpt_2011.pdf
(3.3 MB)
|
