title: Unravelling the relative roles of top-down and bottom-up forces driving population change in an oceanic predator.
abstract: In the open ocean ecosystem, climate and anthropogenic changes have driven biological change at both ends of the food chain. Understanding how the population dynamics of pelagic predators are simultaneously influenced by nutrient-driven processes acting from the "bottom-up" and predator-driven processes acting from the "top-down" is therefore considered an urgent task. Using a state-space demographic model, we evaluated the population trajectory of an oceanic predator, the Macaroni Penguin (Eudyptes chrysolophus), and numerically assessed the relative importance of bottom-up and top-down drivers acting through different demographic rates. The population trajectory was considerably more sensitive to changes in top-down control of survival compared to bottom-up control of survival or productivity. This study integrates a unique set of demographic and covariate data and highlights the benefits of using a single estimation framework to examine the links between covariates, demographic rates and population dynamics.
authors.affiliation: British Antarctic Survey, High Cross, Cambridge, CB3 0ET, United Kingdom.|Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, United Kingdom.
authors.forename: C
authors.initials: C
authors.lastname: Horswill
authors.affiliation: British Antarctic Survey, High Cross, Cambridge, CB3 0ET, United Kingdom.
authors.forename: N
authors.initials: N
authors.lastname: Ratcliffe
authors.affiliation: School of Environmental Sciences, University of Liverpool, Liverpool, L69 3GP, United Kingdom.
authors.forename: J A
authors.initials: JA
authors.lastname: Green
authors.affiliation: British Antarctic Survey, High Cross, Cambridge, CB3 0ET, United Kingdom.
authors.forename: R A
authors.initials: RA
authors.lastname: Phillips
authors.affiliation: British Antarctic Survey, High Cross, Cambridge, CB3 0ET, United Kingdom.
authors.forename: P N
authors.initials: PN
authors.lastname: Trathan
authors.affiliation: Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, United Kingdom.
authors.forename: J
authors.initials: J
authors.lastname: Matthiopoulos
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000502:physiology*; D017753:Ecosystem; D020387:Food Chain; D009792:Oceans and Seas; D011157:Population Dynamics; D011235:Predatory Behavior
keywords: El Niño Southern Oscillation; Macaroni Penguin (Eudyptes chrysolophus); Monte Carlo Markov chain; density dependence; population model; predation; sea surface temperature; seabird; stochastic variable selection