Distribution of megafaunal species in the Southwestern Atlantic: key ecological areas and opportunities for marine conservation

Abstract

During the last centuries, populations of marine megafauna—such as seabirds, turtles, and mammals—were intensively exploited. At present, other threats such as bycatch and pollution affect these species, which play key ecological roles in marine ecosystems as apex consumers and/or nutrient transporters. This study analyses the distribution of six megafaunal species (Chelonia mydas, Caretta caretta, Dermochelys coriacea, Thalassarche melanophris, Otaria flavescens, and Arctocephalus australis) coexisting in the Southwestern Atlantic to discuss their protection in terms of current management strategies in the region. Through the prediction of the species potential distributions and their relation to bathymetry, sea temperature and oceanographic fronts, key ecological areas are defined from a multi-taxa perspective. Information on the distribution of 70 individuals (18 sea turtles, 19 albatrosses, and 33 otariids) was obtained through satellite tracking conducted during 2007–2013 and analysed using a Geographic Information System and maximum entropy models. During the autumn–winter period, megafaunal species were distributed over the continental shelves of Argentina, Uruguay, and Brazil, mainly over the Argentine Exclusive Economic Zone and the Argentina-Uruguay Common Fishing Zone. Despite some differences, all megafaunal species seems to have similar environmental requirements during the autumn–winter period. Mostly waters shallower than 50 m were identified as key ecological areas, with the Río de la Plata as the habitat with the highest suitability for all the species. This area is highly productive and sustains the main coastal fisheries of Uruguay and Argentina, yet its role as a key ecological area for megafaunal species has been underestimated until now. This approach provides a basis to analyse the effect of anthropic activities on megafaunal species through risk maps and, ultimately, to generate knowledge to improve national and bi-national management plans between Argentina and Uruguay.

Female-biased stranding in Magellanic penguins

“…Several factors might threaten Magellanic penguins along the coasts from northern Argentina to southern Brazil. Although individual penguins that travel northward can exploit the areas of higher primary and secondary productivity provided by the Río de la Plata plume [8], winter oceanographic conditions, for example a larger plume [7], probably reduce their foraging effi ciency and disperse prey species. This might necessitate additional energy expenditure by penguins with respect to locating and capturing prey [7] or by migrating farther north [1] and encountering the oligotrophic southward-fl owing Brazilian Current, all of which could contribute to a deterioration in body condition.…”

“…This might necessitate additional energy expenditure by penguins with respect to locating and capturing prey [7] or by migrating farther north [1] and encountering the oligotrophic southward-fl owing Brazilian Current, all of which could contribute to a deterioration in body condition. In addition, areas of the Río de la Plata plume front sustain industrial fi sheries [8], and petroleum chronic pollution has been a serious concern from southern Brazil through northern Argentina (see more details in the Supplemental Information). These natural and anthropogenic factors likely increase the probability of stranding, and particularly so in females, as more females than males tend to frequent northern areas; this phenomenon presumably relates to the female bias in the stranding of Magellanic penguins ( Figure 1C).…”

“…Such sexual differences in spatial domains might be driven by mechanisms related to sexual size dimorphism, such as the avoidance of intraspecifi c competition for food resources [4], differences in thermal habitat preference [5] or differences in the ability to withstand the northwardfl owing ocean circulation [6]. Individual penguins that winter in northern areas are likely to be at greater risk of natural [7] and anthropogenic threats [8], and probably more so in females, as more females than males tend to frequent areas closer to the sites where penguins strand. Our results highlight the importance of understanding the spatial domains of each sex throughout the annual cycle that are associated with different mortality risks.…”

Avian SDMs: current state, challenges, and opportunities

“…All these data have great potential for use in SDM approaches, e.g. to define conservation areas (González Carman et al 2016) and to improve our understanding of seabird ecology (Quillfeldt et al 2015).…”

“…For example, high-resolution tracking data have been used to compare sex differences in habitat relationships of penguins (Ludynia et al 2013) or to assess the marine distribution of black-browed albatrosses Thalassarche melanophris in areas important for fisheries (González Carman et al 2016), whereas boat-based surveys and seabird tracking data have been used to identify foraging hotspot areas off the Mediterranean Iberian coast (Arcos et al 2012) and California (McGowan et al 2013). However, especially for small species, technical issues prevent tracking devices from recording high-resolution occurrence data.…”