Spatio‐temporal dynamics of ocean conditions and forage taxa reveal regional structuring of seabird–prey relationships. Issue 7 (1st October 2014)

• Record Type: Journal Article
• Authors: Santora, Jarrod A.; Schroeder, Isaac D.; Field, John C.; Wells, Brian K.; Sydeman, William J.
• Is Part Of: Ecological applications. Volume 24:Issue 7(2014)
• Page Start: 1730
• Page End: 1747
• Publication Date: 2014-10-01
• Subjects: anchovy -- demographic response -- ecosystem oceanography -- forage fish -- krill -- management -- preyscape -- seabird reproduction -- seascape -- upwelling; Ecology -- Periodicals; Environmental protection -- Periodicals; Biology, Economic -- Periodicals; 577.05
• DOI: 10.1890/13-1605.1
• Languages: English
• ISSNs: 1051-0761

Abstract

Abstract : Studies of predator–prey demographic responses and the physical drivers of such relationships are rare, yet essential for predicting future changes in the structure and dynamics of marine ecosystems. Here, we hypothesize that predator–prey relationships vary spatially in association with underlying physical ocean conditions, leading to observable changes in demographic rates, such as reproduction. To test this hypothesis, we quantified spatio‐temporal variability in hydrographic conditions, krill, and forage fish to model predator (seabird) demographic responses over 18 years (1990–2007). We used principal component analysis and spatial correlation maps to assess coherence among ocean conditions, krill, and forage fish, and generalized additive models to quantify interannual variability in seabird breeding success relative to prey abundance. The first principal component of four hydrographic measurements yielded an index that partitioned "warm/weak upwelling" and "cool/strong upwelling" years. Partitioning of krill and forage fish time series among shelf and oceanic regions yielded spatially explicit indicators of prey availability. Krill abundance within the oceanic region was remarkably consistent between years, whereas krill over the shelf showed marked interannual fluctuations in relation to ocean conditions. Anchovy abundance varied on the shelf, and was greater in years of strong stratification, weak upwelling and warmer temperatures. Spatio‐temporal variability of juvenile forage fish co‐varied strongly with each other and with krill, but was weakly correlated with hydrographic conditions. Demographic responses between seabirds and prey availability revealed spatially variable associations indicative of the dynamic nature of "predator–habitat" relationships. Quantification of spatially explicit demographic responses, and their variability through time, demonstrate the possibility of delineating specific critical areas where the implementation of protective measures could maintain functions and productivity of central place foraging predators.