Minnesota Landowners and Fishers - Ryan Pennesi Photography

Minnesota Landowners: Fishers need your help


Figure 1. A fisher (Martes pennanti) captured by a motion triggered camera in northeast Minnesota.

Figure 1. A fisher (Martes pennanti) captured by a motion triggered camera in northeast Minnesota.

The Fisher: Species Profile  


The fisher (Martes pennanti), a medium-sized forest carnivore in the weasel family, is just beginning to be the focus of increased research and conservation efforts in the northeast region of Minnesota (Spring, 2019). Fishers are adaptable predators which have diets consisting of small mammals, rodents, birds, reptiles, spiders, insects, and some plants (Zielinski, 1999).


Conservation Need


According to a recent article in the Minnesota Conservation Volunteer magazine, the species population has decreased by roughly half since 2002 (Spring, 2019 & Joyce, 2019). Furbearer research scientist, John Erb (with the Minnesota Department of Natural Resources), attributes the decline of fishers to habitat loss and change. It has been hypothesized that a general lack of large diameter trees in the northeast Minnesota forested landscape may be threatening long-term fisher population survival (Spring, 2019). A study by Erb et al. (2016) from 2009-2015 showed three main findings in regards to fisher reproductive ecology in Minnesota. 1) Females fishers are obligate cavity nesters--meaning they raise their kits in cavities of large-diameter trees. 2) Cavity trees are critically important for reproduction, providing protection from predators. 3) Large cavity trees are relatively scarce in managed forests of the northeast region.

Fisher Research and Den Boxes:


Currently there are research efforts underway by the Natural Resources Research Institute (NRRI)--a branch of the University of Minnesota. The NRRI has currently secured funds to research the effectiveness of artificial den boxes as habitat enhancement for fishers (Joyce, 2019). The research will specifically focus on comparing managed forests, where a lack of large diameter trees may be threatening long-term fisher population survival. If artificial den boxes do enhance habitat, their installation in managed forests may help make up for a lack of larger diameter trees due to logging activities. Human-economic and subsistence factors would be less impacted if artificial den boxes allow some timber harvest to continue in the region.

Attention Minnesota Landowners


In order for conservation efforts to be long-lasting and effective, there needs to be human community support surrounding the goals of those projects (Kareiva, 2012). I am asking for the attention of Minnesota landowners to this issue because you can help secure the fishers future. 

A male fisher investigates a den box in Wright, MN (Photo courtesy Carlton County Land Department).

A male fisher investigates a den box in Wright, MN (Photo courtesy Carlton County Land Department).

An American marten at a carnivore monitoring station

An American marten at a carnivore monitoring station

A fisher at a carnivore monitoring station

A fisher at a carnivore monitoring station


Literature Cited:


Erb, John & Coy, Pamela & Sampson, Barry. (2016). REPRODUCTIVE ECOLOGY OF FISHERS AND AMERICAN MARTENS IN MINNESOTA.


Furnas, B.J., Landers, R.H., Callas, R.L. & Matthews, S.M. (2017). Estimating population size of fishers Pekania pennanti using camera stations and auxiliary data on home range size. Ecosphere 8, e01747.


Joyce, Michael. (2019). Environment and Natural Resources Trust Fund (ENRTF) M.L. 2019 ENRTF Work Plan (Main Document). Subd. 03i


Kareiva, P., & Marvier, M. (2012). What is conservation science? BioScience, 62(11), 962-969.


Spring, Joe. (2019). Field Notes: New dens for fishers. Minnesota Conservation Volunteer Magazine (MCV)


Zielinski, W.J., Duncan, N.P, Farmer, C.F., Truex, R.L, Clevenger, A.P. & Barrett, R.H. (1999). Diet of fishers (Martes pennanti) at the southernmost extent of their range. J. Mammal. 80, 961–971.

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