DOI: 10.5061/dryad.mh4vh5v
title: Data from: The sensitivity of seabird populations to density-dependence, environmental stochasticity and anthropogenic mortality

description: 1.The balance between economic growth and wildlife conservation is a
 priority for many governments. Enhancing realism in assessment of
 population‐level impacts of anthropogenic mortality can help achieve this
 balance. Population Viability Analysis (PVA) is commonly applied to
 investigate population vulnerability, but outcomes of PVA are sensitive to
 formulations of density‐dependence, environmental stochasticity and
 life‐history. Current practice in marine assessments is to use
 precautionary models that assume no compensation from density‐dependence
 or rescue‐effects via “re‐seeding” from other colonies. However, if we
 could empirically quantify regulatory population processes, the responses
 of populations to additional anthropogenic mortality may be assessed with
 more realism in PVA. 2. Using Bayesian state‐space models fitted to
 population time‐series from three sympatric seabird populations, selected
 for varied life histories, we inferred the extent to which their dynamics
 are driven by environmental stochasticity and density‐dependence. 3. Based
 on these inferences, we conducted an exhaustive PVA across credible
 parameterisations for intrinsic and extrinsic population regulation,
 simulated as a closed and re‐seeded system. Scenarios of anthropogenic
 mortality, along a sliding scale of precaution, were applied both
 proportionally and as a fixed quota using Potential Biological Removal
 (PBR). 4. Baseline results from fitting revealed clear environmental
 regulation in two of our three species. Crucially, we found that for our
 empirically derived, realistic model parameterisations there are risks of
 decline to real populations even under very precautionary mortality
 scenarios. We find that PBR is dubious in application as a sustainable
 tool for population assessment when we account for regulation. Closed
 versus re‐seeded models showed a large divergence in outcomes, with
 sharper declines in closed simulations. Fixed‐quota mortality typically
 induced greater population declines comparative to proportional mortality,
 subject to regulation and re‐seeding. 5. Synthesis and applications:
 Practitioners using arbitrary formulations of population regulation risk
 over‐precaution (economic constraint) or under‐precaution (endangering
 populations). The demands of increased economic development and
 preservation of wildlife require that methodologies apply techniques that
 confer reality and rigour to assessment. The current practice of employing
 models lacking density‐dependence and empirical environmental information
 imposes limitations in the efficacy of estimating impacts. Here, we
 provide a method to quantify the conditions that predominantly regulate a
 population and exacerbate the risk of decline from anthropogenic
 mortality. It is in the interests of both developers and conservationists
 to apply methods in population impact assessments that capture realism in
 the processes driving population dynamics.
description: Miller et al. 2019.
 Model_code_and_dataThis additional material
 provides data used and reproducible code for models.JPEMillerSA2.docx