Impact of hunting along the migration corridor of pink-footed geese Anser brachyrhynchus — implications for sustainable harvest management

• Published in: The Journal of applied ecology Vol. 54; no. 5; pp. 1563 - 1570
• Main Authors: Clausen, Kevin Kuhlmann, Christensen, Thomas Kjær, Gundersen, Ove Martin, Madsen, Jesper
• Format: Journal Article
• Language: English
• Published: Oxford John Wiley & Sons Ltd 01.10.2017; Blackwell Publishing Ltd
• Subjects: Age composition; age ratio bias; Animal populations; Aquatic birds; Bird migration; Breeding; Demography; geese; Growth rate; harvest rate; Hunting; Juveniles; Natural populations; population management; Quarries; Sex ratio; survival; Sustainability; sustainable harvest; waterfowl; Wildfowl; Wildlife management
• ISSN: 0021-8901; 1365-2664
• DOI: 10.1111/1365-2664.12850

1. Hunting can potentially affect population size, age composition, sex-ratio, behaviour and distribution of natural populations, and understanding its impacts is a prerequisite to manage quarry species sustainably. Harvest management relies strongly on the existence of both strictly regulated hunting efforts and efficient monitoring of populations, their demography and harvest. These conditions are rarely met in practice. 2. For the Svalbard-breeding population of the pink-footed goose Anser brachyrhynchus, an internationally coordinated adaptive harvest management framework enables a flyway-based assessment of harvest impact. Based on 25 years of population assessment and harvest data, we evaluate the differential impact of harvest along the migration corridor of the population. 3. The analysis reveals that (i) total harvest and harvest rate (proportion of the population killed by hunting) have increased substantially in recent years, (ii) compared to adult geese, juveniles were overrepresented in the hunting bag by a factor of 3-7, (iii) the proportion of juveniles in the hunting bag differed between the two countries (Norway and Denmark) with an open season, and was more than twice as high in the former compared to the latter, and (iv) the increase in harvest rate seemed to be driven by increased hunting mortality of juvenile birds, with no clear impact on the growth rate of the population. However, this may partly relate to the transient dynamics and population inertia commonly seen in long-lived species such as geese, and a 3-year consecutive decline towards the end of our study period might be the first signs of an impending decline. 4. Synthesis and applications. Our findings highlight that the impact of harvest varies along the migration corridor and between age classes of a single species and suggest that allocation of hunting effort in time and space is important to optimise harvest. Our example demonstrates the need for internationally coordinated, detailed population and harvest data which are essential for sustainable harvest management.