Data from: An integrated assessment model of seabird population dynamics: can individual heterogeneity in susceptibility to fishing explain abundance trends in Crozet wandering albatross?

1. Seabirds have been incidentally caught in distant-water longline fleets
operating in the Southern Ocean since at least the 1970s, and breeding
numbers for some populations have shown marked trends of decline and
recovery concomitant with longline fishing effort within their
distributions. However, lacking is an understanding of how forms of
among-individual heterogeneity may interact with fisheries bycatch and
influence population dynamics. 2. We develop a model that uses
comprehensive data on the spatial and temporal distributions of fishing
effort and seabird foraging to estimate temporal overlaps, fishery
catchability and consequent bycatch. We apply a population model that is
structured by age, sex, life stage and spatially to Crozet Island
wandering albatross and explore how heterogeneity in susceptibility to
capture may have influenced the population's demography over time. 3.
A model where some birds were assumed to be more susceptible to fisheries
bycatch was able to successfully replicate the observed trend in breeding
pairs. Considerably poorer fits were found without this assumption.
Results suggested that the more susceptible birds may have been removed
from the population by the 1990s. 4. The model was also able to highlight
areas, times and fleets prone to increased bycatch. Knowledge of these
factors should assist fisheries and conservation management bodies to
quantify and reduce seabird bycatch through spatial management and
fleet-specific mitigation efforts. 5. Synthesis and application. Many
seabirds show complex life histories that make them highly susceptible to
additional incidental mortality from fishing vessels. By applying a
population model that integrates key aspects of seabird and fishery
dynamics, we were able to explain the observed trends in the breeding
population of Crozet wandering albatross and identify key areas and fleets
where further mitigation may be required. In addition, the potential
removal of a category of birds that shows increased susceptibility to
capture has important implications for the conservation management of this
population and other iconic species incidentally caught by large-scale
commercial fisheries.