Harvesting a red-listed species: determinant factors for willow ptarmigan harvest rates, bag sizes, and hunting efforts in Norway

Jo Inge Breisjøberget,Morten Odden,Torstein Storaas,Erlend B Nilsen,Mikkel A J Kvasnes

doi:10.1007/s10344-018-1208-8

Abstract

A main objective of game management on public lands in Norway is to ensure that harvest levels are sustainable while securing hunting access to the public. The willow ptarmigan is a popular but red-listed small game species, and it is challenging for managers to optimize harvest levels based on uncertain population estimates and limited knowledge of the factors influencing hunting impact. We studied how willow ptarmigan hunting effort, catch per unit effort, and harvest rates were influenced by ptarmigan density, topography, vegetation, and infrastructure. Data were collected during 2013–2016 from 162 hunting blocks covering 26,828 km2 state-owned land in the counties Nordland and Troms, northern Norway. Hunting effort averaged 1.27 days/km2 (SD = 2.08), and it was the highest in areas close to roads and cabins. We found an opposite effect on the catch per unit effort (CPUE, mean = 0.77 ptarmigan/day, SD = 0.48), which was lower close to roads. There was a marked positive effect of density on CPUE, whereas terrain steepness (slope) had a negative effect. On average, harvest removed < 10% of the autumn population in the hunting areas during the study period. This indicates a relatively low and partially compensatory hunting mortality in most years and areas. Although this study shows a low harvest rate, we recommend managers to survey ptarmigan populations, hunting effort, and harvest, especially in easily accessible areas close to infrastructure and in periods of low population density.

Highlights

For a harvest regime to be sustainable, annual harvest rates should not exceed net population growth rates over a long time span (Boyce et al 1999; Getz and Haight 1989; Hilborn et al 1995; Lande et al 1995)
Environmental and/or demographic stochasticity may lead to rapid population fluctuations that further complicate the adoption of a sound level of harvest (Engen et al 1997)
In order to disentangle the relative importance of different factors affecting ptarmigan harvest, we focused on three aspects: (1) hunting effort; (2) hunter efficiency, i.e., catch per unit effort; and (3) ptarmigan harvest rate

Summary

Introduction

For a harvest regime to be sustainable, annual harvest rates should not exceed net population growth rates over a long time span (Boyce et al 1999; Getz and Haight 1989; Hilborn et al 1995; Lande et al 1995). There is often not a clear and simple link between harvest regulations and harvest off-take in these game management systems (Johnson and Williams 1999). An example of this is the willow ptarmigan (Lagopus lagopus), hereafter ptarmigan, whose high intrinsic rate of increase and highly variable breeding success produce marked annual variation in abundance (Henden et al 2011; HörnellWillebrand 2005; Kvasnes et al 2010; Moss and Watson 2001; Myrberget 1988)

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Conclusion