Abstract
The protection of key areas for biodiversity at sea is not as widespread as on land and research investment is necessary to identify biodiversity hotspots in the open ocean. Spatially explicit conservation measures such as the creation of representative networks of marine protected areas (MPAs) is a critical step towards the conservation and management of marine ecosystems, as well as to improve public awareness. Conservation efforts in ecologically rich and threatened ecosystems are specially needed. This is particularly urgent for the Mediterranean marine biodiversity, which includes highly mobile marine vertebrates. Here, we studied the at sea distribution of one of the most endangered Mediterranean seabird, the critically endangered Balearic shearwater Puffinus mauretanicus. Present knowledge, from vessel-based surveys, suggests that this species has a coastal distribution over the productive Iberian shelf in relation to the distribution of their main prey, small pelagic fish. We used miniaturised satellite transmitters to determine the key marine areas of the southern population of Balearic shearwaters breeding on Eivissa and spot the spatial connections between breeding and key marine areas. Our tracking study indicates that Balearic shearwaters do not only forage along the Iberian continental shelf but also in more distant marine areas along the North African coast, in particular W of Algeria, but also NE coast of Morocco. Birds recurrently visit these shelf areas at the end of the breeding season. Species distribution modelling identified chlorophyll a as the most important environmental variable in defining those oceanographic features characterizing their key habitats in the western Mediterranean. We identified persistent oceanographic features across time series available in the study area and discuss our results within the current conservation scenario in relation to the ecology of the species.
Highlights
The protection of key areas for biodiversity at sea is not as widespread as on land and research investment is necessary to identify biodiversity hotspots in the open ocean
Our tracking study clearly indicates that Balearic shearwaters do forage along the Iberian continental shelf, and in more distant key marine areas located along the northern African coast, as suggested by early satellite tracking from Menorca [12,16]
Productivity is high at the offshore band of the Algerian Current where high concentrations of nutrients and chlorophyll a are related to high zooplankton biomass levels and abundances [38,42]
Summary
The protection of key areas for biodiversity at sea is not as widespread as on land and research investment is necessary to identify biodiversity hotspots in the open ocean. Conservation efforts in ecologically rich and threatened ecosystems are especially needed, urgently for the Mediterranean Sea [2] This marine ecosystem is diverse showing both high degree of endemism (around 20–30%) [3] and high occurrence of threatened species [1], covering only 0.3% of the global oceans while hosting 7% of the world’s marine species [3]. Current protected areas (namely MPAs) do not constitute a representative network since most of them are located in shallow waters of the northern part of the basin and represent 3.8% of the total surface of the Mediterranean Sea [1] This may be a consequence of the limited marine research efforts of several eastern and southern regions of the Mediterranean [4], which could have delayed the implementation of protected areas in these biogeographic areas. Ecologically important habitats of high conservation value (especially those identified in the southern and eastern Mediterranean), including pelagic habitats of highly mobile marine vertebrates [1], should be protected
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