Spatial match–mismatch in the Benguela upwelling zone: should we expect chlorophyll and sea‐surface temperature to predict marine predator distributions?

Abstract

Summary 1.Remote-sensing measurements of marine primary productivity are widely used to predict the distribution and movements of marine top predators, despite the fact that predators do not feed directly on phytoplankton but several trophic levels higher up the food chain. 2. To test for potential links between primary productivity and top-predator feeding hotspots, we assessed spatial match-mismatch across four trophic levels of the Benguela upwelling zone (south-east Atlantic). The food chain studied consisted of phytoplankton, zooplankton (copepods), pelagic fish (anchovies and sardines) and two top predators (Cape gannets Morus capensis and human fisheries). 3. Remote-sensing data of sea-surface temperature (SST) and chlorophyll_a concentration were used as indices of phytoplankton abundance throughout the study area. Copepod biomass and pelagic fish density were determined during at-sea surveys in the South African section of the Benguela using net tows and hydro-acoustics, respectively. Seabird (Cape gannet) home ranges and foraging zones were assessed from two Namibian breeding colonies (Mercury and Ichaboe) and two South African colonies (Lambert's Bay and Malgas) using global positioning system (GPS) tracking. Industrial fishing for anchovies and sardines was investigated using South African landing statistics and logbooks. 4. Our spatial analyses revealed a strong match of seabird at-sea habitat and zones of high primary productivity throughout the southern Benguela. Conversely, there was a marked spatial mismatch between copepods and pelagic fish, as well as between pelagic fish, seabirds and human fisheries: copepods were present in the southern Benguela but pelagic fish usually feeding upon them were located further east (Indian Ocean), outside of the Benguela sensu stricto . Consequently, the majority of these pelagic fish were out of reach for seabirds and fisheries confined to the southern Benguela. 5. Synthesis and applications . Our study demonstrates the impact of an ecosystem shift across one of the world's most productive marine ecosystems and highlights the limitations of using remotesensed patterns of primary productivity to interpret the foraging behaviour of marine top predators. These findings underline the importance of a better knowledge of food web spatial dynamics to support ecosystem-based fisheries management and the conservation of marine top predators.

Foraging areas of streaked shearwaters in relation to seasonal changes in the marine environment of the Northwestern Pacific: inter-colony and sex-related differences

“…In both colonies, however, foraging areas for females did not always coincide with areas of higher chl a concentration (Table 3). This could be explained, in part, by the time lags between increased primary productivity and associated increase in the availability of shearwater prey (Odate 1994, Suryan et al 2006, Grémillet et al 2008. Furthermore, the distribution of pelagic fishes that shearwaters mainly feed on is affected directly by SST (Oozeki et al 2007, Takasuka et al 2008a.…”

Global positioning system and associated technologies in animal behaviour and ecological research

“…Finally, the GPS system provides accurate time stamping of a position. When GPS was coupled with data transmission technologies (Rempel et al 1995;Rodgers et al 1996;Schwartz & Arthur 1999), a new era of animal tracking began, and recent literature contains numerous examples of successful studies using GPS positioning (Godley et al 2008;Gremillet et al 2008;Laurian et al 2008;Trathan et al 2008;Van Beest et al 2010).…”

“…Fuelled by the requirement in the United States to be able to locate all mobile phones in emergencies, GPS engines became smaller and more energy-efficient, and therefore more usable for animal-tracking applications. Smaller, low-voltage (3.0 Vdc) and low-current (less than 30 mA) receivers are better integrated with battery-powered systems that now allow tracking of smaller mammalian species and, more recently, birds (Ryan et al 2004;Meyburg et al 2006Meyburg et al , 2007Gremillet et al 2008;Mandel et al 2008), which for some species requires special attachments (e.g. Tyler & Flint 2008).…”

A novel spatio-temporal scale based on ocean currents unravels environmental drivers of reproductive timing in a marine predator

“…Whereas local environmental features could have been targeted by selective pressures for reproductive timing in low dispersive species (e.g. sedentary species [10]), large-scale environmental cues (e.g. global climate indices) should be the ones probably implemented as drivers of reproductive timing in high dispersive species (e.g.…”