Re-Examining Mortality Sources and Population Trends in a Declining Seabird: Using Bayesian Methods to Incorporate Existing Information and New Data

Tim Reid,Mark Hindell,Chris Wilcox,Jennifer L Lavers,Yan Ropert-Coudert

doi:10.1371/journal.pone.0058230

Abstract

The population of flesh-footed shearwaters (Puffinus carneipes) breeding on Lord Howe Island was shown to be declining from the 1970's to the early 2000's. This was attributed to destruction of breeding habitat and fisheries mortality in the Australian Eastern Tuna and Billfish Fishery. Recent evidence suggests these impacts have ceased; presumably leading to population recovery. We used Bayesian statistical methods to combine data from the literature with more recent, but incomplete, field data to estimate population parameters and trends. This approach easily accounts for sources of variation and uncertainty while formally incorporating data and variation from different sources into the estimate. There is a 70% probability that the flesh-footed shearwater population on Lord Howe continued to decline during 2003–2009, and a number of possible reasons for this are suggested. During the breeding season, road-based mortality of adults on Lord Howe Island is likely to result in reduced adult survival and there is evidence that breeding success is negatively impacted by marine debris. Interactions with fisheries on flesh-footed shearwater winter grounds should be further investigated.

Highlights

Marine vertebrates, such as seabirds, turtles, fish and cetaceans face a number of significant threats [1,2]
While most studies focus on individual threats to populations, a number of recent studies have highlighted the need to consider multiple threats concurrently in order to improve our understanding of the overall status of a population, and how best to conserve it [7,8]
Flesh-footed shearwaters are listed as Vulnerable in New South Wales, as the states only breeding colony (Lord Howe Island) has been declining since 1978 [12]

Summary

Introduction

Marine vertebrates, such as seabirds, turtles, fish and cetaceans face a number of significant threats [1,2]. Seabirds are relatively long-lived animals that exhibit delayed breeding and low fecundity, any additional adult mortality will have considerable demographic consequences. This life-history strategy presents challenges for researchers attempting to estimate population dynamics and manage multiple threats. While most studies focus on individual threats to populations, a number of recent studies have highlighted the need to consider multiple threats concurrently in order to improve our understanding of the overall status of a population, and how best to conserve it [7,8]. This can be most readily achieved with studies in locations where some level of accuracy on the full range of threats can be obtained

Objectives

Methods

Results

Conclusion