DOI: 10.5061/dryad.dbrv15f1w
title: Mast productivity, red-backed vole productivity and rate of increase, northern saw-whet owl rate of increase, and fisher harvest age ratios for central Ontario, 1994-2016

description: Harvest management quotas for fishers (Pekania pennanti) in some
 jurisdictions are estimated from the previous year’s harvest, and stem
 from the hypothesis that age ratios in the harvest are largely influenced
 by ‘top-down’ trapping pressure.  The influence of ‘bottom-up’
 food supply on fisher harvest age ratios might be underappreciated, which
 could result in a misallocation of quotas in management planning. We
 assessed a variety of data sources to test the influence of bottom-up
 processes on fisher populations in Ontario, Canada. We found evidence that
 bottom-up trophic effects influence the harvested fisher age structure in
 some regions of Ontario. Evidence also suggests that harvest pressure had
 little top-down influence on age ratios over the course of our study, and
 that basing management strategies on this assumption may lead to
 unintentional overharvest in years of low productivity.  We
 suggest several trophic linkages with potential to facilitate fisher
 management, including connections among berry and seed crops, small
 mammals, and Northern saw-whet owls (Aegolius acadicus).
description: Our study took place in the Great Lakes-St. Lawrence East region
 of Ontario, which encompasses the southern range boundary of fishers
 within the province.  We received fisher harvest data from 11 fur
 management units (FMUs) within this region - Owen Sound, Huronia,
 Peterborough, Mazinaw, Bancroft, Carleton Place, Brockville, Cornwall,
 Pembroke, Parry Sound, and Bracebridge.  Following the harvest, fisher
 trappers were invited to submit skulls, jaws, or teeth to their local
 Ontario Ministry of Natural Resources and Forestry (OMNRF) office. 
 Wildlife managers then aged submissions by x-raying the teeth and
 measuring pulp cavity width (Dix and Strickland 1986).  We used these data
 to determine juvenile:adult female (J:AF) ratio for each FMU for each
 year.  Fishers were considered adults if they were &gt;1.5 years of
 age.  Red-backed vole abundance was determined from an
 ongoing annual trapping program in Algonquin Provincial Park, which has
 been described in several published articles (e.g., Fryxell et al. 1998,
 1999, Falls et al. 2007, Denomme-Brown et al. 2020).  Small mammals were
 trapped once or twice a month, May-August, at 10 trap lines along the
 Highway 60 corridor of the park.  Each trapline was approximately 90 m
 long and contained 10 trapping stations spaced 10 m apart, each with two
 small (7.5 cm x 7.5 cm x 30.5 cm) Sherman live traps.  One Sherman and one
 Longworth trap (6.4 cm x 8.4 cm x 13.8 cm) were used for the years 2013 to
 2016 inclusive.  Therefore, each line contained a total of 20 traps. 
 Traps contained a ball of polyester batting for use as bedding and were
 baited each evening with water-soaked sunflower seeds, oats, or peanut
 butter and checked the following morning.  Captured animals were
 identified to species and marked with a Monel ear tag.  We calculated
 species abundance as the number of captures per 100 trap nights (TN) and
 exponential rate of increase as the natural logarithm of the ratio of the
 abundance at time <i>t</i> and the abundance the previous
 year, at time <i>t</i>-1.  The annual mean (SD) trap nights
 for our 23 years of data was 4678 (±427). We collected
 data on the productivity of mountain ash and oak from the OMNRF’s annual
 Ontario Wildlife Food Survey.  To complete this survey, OMNRF field
 personnel submitted estimated summer and fall fruit/seed productivity
 scores for a range of plant species from their region on a scale of 0-4,
 with 0 indicating no or almost no production and 4 indicating a bumper
 crop.  For the purposes of our study we considered only data from the
 Great Lakes-St. Lawrence East region of Ontario.  We excluded data from
 three districts within this region (Sault Ste. Marie, Wawa, and Aylmer)
 because they did not overlap with and were not adjacent to the FMUs
 included in our study.  There was variation in reporting strategy within
 and among districts. For example, some districts submitted multiple
 observations from specific locations within the district while others
 provided an overall estimate.  For comparability, mean annual productivity
 scores for each reporting area were weighted equally to calculate a mean
 overall productivity score for each species of interest over the entire
 study area.   We estimated relative abundance of
 Northern saw-whet owls using data collected during Birds Canada Nocturnal
 Owl Surveys in the central region of Ontario, which is roughly bordered by
 the 47<sup>o</sup>N and 44<sup>o</sup>N lines of
 latitude.  Surveys were conducted annually on a single evening in April by
 volunteers following a predetermined 18 km route.  These routes were
 located along secondary roads and consisted of 10 stops spaced 2 km
 apart.  The protocol at each stop began with 2 min of silent listening for
 owl calls, followed by the playing of a series of boreal owl
 (<i>Aegolius funereus</i>) and barred owl (<i>Strix
 varia</i>) calls interspersed with silent listening periods. 
 Volunteers recorded all owl calls they heard at each station.  Birds
 Canada personnel then estimated an annual index for each owl species,
 including Northern saw-whet owl, using generalized additive models with
 smoothing terms for geographic location to account for spatial
 autocorrelation.  The response variable was the number of occupied
 stations on each route for a given year.  Models were created using the
 binomial version of the “gam” function, which is based on the methods of
 Hastie (1992) and found in the GAM package for R.  Using the indices
 produced by this calculation (N) we calculated northern saw-whet owl
 exponential rate of increase in year <i>t</i> using the
 formula
 ln(N<sub>t</sub>/N<sub>t-1</sub>).  
description: Fisher J:AF values for each FMU are presented in the columns
 labelled with the FMU names. Fisher age ratios were
 calculated over the entire fisher trapping season (October-January).  Data
 is presented in the row corresponding to the year in which the trapping
 season began (i.e. J:AF data in the "1998" row corresponds to
 the 1998-1999 trapping season). Blank cells indicate
 that data was not available.