Potential global distribution of a temperate marine coastal predator: The role of barriers and dispersal corridors on subpopulation connectivity

Predicting the potential distribution of species and possible dispersal corridors at a global scale can contribute to better understanding the availability of suitable habitat to move between, and the potential connectivity between regional distributions. Such information increases knowledge of ecological and biogeographic processes, but also has management applications at a global scale, for example, for estimating the restocking ability of exploited regional subpopulations. As a case study, we tested the utility of environmental niche modeling to investigate the potential global distribution of a highly mobile temperate marine coastal species, the broadnose sevengill shark (Notorynchus cepedianus). First, we characterized and compared three model variants using global data and regional data from two geographically distant and genetically diverging subpopulations in the Southwest Atlantic and southern Australia. The best performing model was then transferred to the rest of the world to obtain a final global prediction for the species. Predictions revealed broad suitable areas across temperate regions of the Northern and Southern Hemispheres. As a final step, we overlaid underwater seamount data on suitability maps to simulate possible dispersal corridors and regional connectivity. Global subpopulation connectivity and dispersal are discussed in the light of recent genetic evidence, to help explain why unoccupied suitable areas are not currently accessed by the species. This study highlights the potential use of global and regional data for the assessment of habitat suitability of species at a global scale, and provides considerations when applying these models to other highly mobile species

The essential habitat role of a unique coastal inlet for a widely distributed apex predator

Essential habitats support specific functions for species, such as reproduction, feeding or refuge. For highly-mobile aquatic species, identifying essential habitats within the wider distribution range is central to understanding species ecology, and underpinning effective management plans. This study examined the movement and space use patterns of sevengill sharks (Notorynchus cepedianus) in Caleta Valdés, a unique coastal habitat in northern Patagonia, Argentina. Seasonal residency patterns of sharks were evident, with higher detectability in late spring and early summer and lower during autumn and winter. The overlap between the residency patterns of sharks and their prey, elephant seals, suggests that Caleta Valdés functions as a seasonal feeding aggregation site for N. cepedianus. The study also found sexual differences in movement behavior, with males performing abrupt departures from Caleta Valdés and showing increased roaming with the presence of more sharks, and maximum detection probability at high tide. These movements could be related to different feeding strategies between sexes or mate-searching behavior, suggesting that Caleta Valdés may also be essential for reproduction. Overall, this study highlights the importance of coastal sites as essential habitats for N. cepedianus and deepens our understanding of the ecological role of this apex predator in marine ecosystems.All analyses were perfomed using open-access R programming software.Funding provided by: Council on Australia Latin America Relations*Crossref Funder Registry ID: Award Number: year 2019Funding provided by: Shark conservation fund*Crossref Funder Registry ID: Award Number: year 2019Funding provided by: CAPES-UC*Crossref Funder Registry ID: Award Number: Funding provided by: Fondo Nacional de Desarrollo Científico, Tecnológico y de Innovación TecnológicaCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100010751Award Number: FB0002Funding provided by: Agencia Nacional de Investigación y DesarrolloCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100020884Award Number: ICN2019-015Funding provided by: Temaikèn Foundation*Crossref Funder Registry ID: Award Number: year 2019Detection data were collected via passive acoustic telemetry using VEMCO instruments. Temperature and tidal data were downloaded from the web (see manuscript for sources). Shapefiles are self-produced and downloaded from the web (see manuscript and R code for sources)