Combining vessel-based surveys and tracking data to identify key marine areas for seabirds

Abstract

An understanding of the distribution and habitat associations of far-ranging marine predators is being increasingly applied to protect these species from anthropogenic threats at sea (e.g. oil spills and fisheries bycatch). Within this framework, this research on Cory's shearwater Calonectris diomedea integrates vessel-based survey and tracking data to provide 2 distinct, yet complementary, perspectives of the habitats of this species in the western Mediterranean during incubation in June and chick rearing in August of 2007. We used a hierarchical modelling approach to (1) delineate the foraging habitat of the species using vessel-based surveys and (2) identify its feeding habitat based on tracking data within the Information-Theoretic framework. Our habitat modelling analyses suggest that shearwaters respond to complex bio-physical coupling, illustrated by their association with frontal features and elevated ocean productivity. Our models yielded moderate predictions of Cory's shearwater habitats within 2 distinct spatial scales. At the mesoscale, the foraging range of the species comprised the continental and insular shelf-slope waters of the Iberian Peninsula and the Balearic Islands, between the Gulf of Lions to the north and Cape Palos to the south. At the coarse scale, the tracking data highlighted important feeding areas within this larger foraging range: 3 continental shelf-slope 'hotspots' -(1) Gulf of Lions, (2) Cape Creus-Barcelona-Ebro Delta and (3) Cape La Nao-Cape Palos; from north to south -as well as the insular shelf-slope areas around the Balearic Islands. These results match previous observations of the foraging range and feeding patterns of the species, and are consistent with the interpretation of the regional oceanography. This study highlights how the integration of tracking and vessel-based survey data can provide a wider understanding of the predictability of aggregation (i.e. hotspots) and the key oceanographic habitats of far-ranging seabirds at multiple spatial scales. Thus, complementary data integration is a step forward in conservation studies of far-ranging marine top predators. OPEN PEN ACCESS CCESS Contribution to the Theme Section 'Spatiotemporal dynamics of seabirds in the marine environment'Mar Ecol Prog Ser 391: [183][184][185][186][187][188][189][190][191][192][193][194][195][196][197] 2009 weakly swimming prey become concentrated at specific features with enhanced vertical (upwelling/downwelling) and horizontal (convergence/divergence) water flow (e.g. Hammer & Schneider 1986, Franks 1992, Haury et al. 1978. In turn, mobile predators concentrate and forage at these same features in response to elevated localized productivity and dense prey patches (e.g. Rodhouse et al. 1996, Johnston et al. 2005.The increasing awareness of the serious threats that marine top predators face at sea, such as fisheries bycatch and oil spills, has triggered the development of conservation measures to ensure the protection of important key marine areas (e.g. foraging areas and migr...

Exploiting the closest productive area: geographical segregation of foraging grounds in a critically endangered seabird

“…However, marine resources are patchily distributed along this continental shelf system and different mesoscale oceanographic features result in productivity hotspots in the Gulf of Lions, Cape Creus, offshore Barcelona, Ebro Delta and Cape La Nao ( Fig. 1; Louzao et al 2009). Within this context, we predicted that northern, central and southern populations would each exploit the closest productive marine areas within the Iberian continental shelf.…”

“…This dimensionless metric expresses the magnitude of change in each habitat variable, scaled to the maximum value (e.g. Louzao et al 2009). The spatial gradients of chl a and SST indicate the presence of frontal systems, whereas the gradient of bathymetry reflects the presence of topographic features (e.g.…”

Projected poleward shift of king penguins' ( Aptenodytes patagonicus ) foraging range at the Crozet Islands, southern Indian Ocean

“…As there was no obvious evidence of a single best model (w i . 0.90), we applied a model averaging procedure to account for uncertainties in model selection [45,46]. For each breeding stage, a set of models totalling 95 per cent of the Akaike weights was kept and used to calculate model parameters (see [46] for details).…”

Time-in-area represents foraging activity in a wide-ranging pelagic forager

“…Among other factors, MSP relies upon the identification of those areas which are most important to conserve for biological and/or ecological functions (Crowder & Norse 2008). One approach is to identify the core foraging areas of pelagic species, specifically marine top predators (Le Corre et al 2012), because they tend to aggregate in specific areas influenced by increased local productivity and dense prey patches (Louzao et al 2009). …”