Natural and anthropogenic factors affecting the feeding ecology of a top marine predator, the Magellanic penguin

Abstract

Abstract. Understanding how top predators respond to natural and anthropogenically induced changes in their environment is a major conservation challenge especially in marine environments. We used a multidisciplinary approach to explore the mechanisms through which a typical central-place forager, the Magellanic penguin (Spheniscus magellanicus) from the Chubut province of Argentina, responds to variations in oceanic conditions and prey resources. We combined habitat and species distribution modeling with isotopic dietary reconstructions based on blood d 13 C and d 15N values to quantify the role of bathymetry, sea-surface temperature and chlorophyll-a concentration, abundance of conspecifics, and extent of fisheries activities in explaining the foraging and feeding ecology of individuals breeding at different colonies. The at-sea distribution of penguins was tightly coupled with the spatial distribution of their staple prey species, anchovies (Engraulis anchoita), especially in areas over the continental shelf (.200 m depth), with relatively warm water (from 168 to 218C), and moderate abundances of conspecifics (from 50 to 250 individuals). Competition with conspecifics and human fisheries were also identified as important factors explaining penguin diet with decreasing relative contributions of anchovies with increasing abundance of conspecifics and fishing activity. Our multifactorial approach allowed us to simultaneously explore different physical, biological and anthropogenic features likely affecting marine resource availability, and, consequently, driving the feeding and foraging ecology of this central-place forager. Our approach can be extended to a large suite of central-place foragers, thus providing important advances in the way we investigate how to effectively conserve and manage these species.

An adaptive method for identifying marine areas of high conservation priority

“…; Ramírez et al. ), offshore IBAs alone do not fulfill conservation targets, and the reserve network from the IBAs scenario included additional coastal areas near Península Valdés, South of Cabo Blanco, and Tierra del Fuego. Many other coastal areas were also identified as priority areas when IBAs were excluded from the Marxan procedure but added a posteriori to the reserve network output (reference scenario).…”

“…; Ramírez et al. ). Estimates of the total number of individuals per breeding species on a pixel basis were the sum of colony‐specific at‐sea projections (Supporting Information).…”

Will remote sensing shape the next generation of species distribution models?

“…; Ramírez et al. ). Furthermore, the Bio‐ORACLE (ocean rasters for analyses of climate and environment at http://www.bio-oracle.ugent.be), a marine counterpart of the WorldClim database has been developed, consisting of 23 environmental rasters, derived from both satellite‐based and in situ data for modeling the distribution of shallow water marine species at a global scale (Tyberghein et al.…”

“…In the marine realm, sea-surface temperature derived from Aqua MODIS (https://podaac.jpl.nasa.gov/SeaSur-faceTemperature), with global resolutions as fine as 1 9 1 km, has been one of the most influential predictors in SDMs for identifying productivity hotspots and seascape modeling (Louzao et al 2011;Ram ırez et al 2014). Furthermore, the Bio-ORACLE (ocean rasters for analyses of climate and environment at http://www.bio-oracle.ugent.be), a marine counterpart of the WorldClim database has been developed, consisting of 23 environmental rasters, derived from both satellite-based and in situ data for modeling the distribution of shallow water marine species at a global scale (Tyberghein et al 2012).…”

Spatial analysis of carbon isotopes reveals seagrass contribution to fishery food web

“…The relative contribution of different basal carbon sources to crabs was assessed separately for the two surveys using the Bayesian mixing model stable isotope analysis in R (SIAR; Parnell et al 2010, and see Ramírez et al 2014). Based on this species diet of grazing and filter-feeding invertebrates (Hill 1979), and an assumed enrichment of C isotopes (McCutchan et al 2003), we used a trophic enrichment factor (TEF) for crabs of 1% (SD 0.1).…”