Irreplaceable area extends marine conservation hotspot off Tunisia: insights from GPS-tracking Scopoli’s shearwaters from the largest seabird colony in the Mediterranean

Abstract

shearwaters foraging from this colony was not larger than that of birds from much smaller colonies, indicating highly beneficial feeding grounds in the Gulf of Tunis and off Cap Bon. Considering depleted Mediterranean small pelagic fish stocks, supposed to be Scopoli's shearwater prey base, we therefore speculate that birds may now also largely feed on zooplankton, something which is supported by our stable isotopic analyses. Crucially, shearwater at-sea feeding and resting areas showed very little overlap with a conservation hotspot recently defined on the western side of the Gulf of Tunis using meta-analyses of species distributions relative to anthropogenic threats. We therefore propose a major extension to this conservation hotspot. Our study stresses the importance of detailed biotelemetry studies of marine megafauna movement ecology for refining large-scale conservation schemes such as marine protected area networks.Abstract Recent meta-analyses identified conservation hotpots at the scale of the Mediterranean, yet those may be crude by lack of detailed information about the spatial ecology of the species involved. Here, we identify an irreplaceable marine area for >95 % of the world population of the Scopoli's shearwater (Calonectris diomedea), which is endemic to the Mediterranean and breeds on the island of Zembra off Tunis. To this end, we studied the threedimensional at-sea movements of 50 breeding adults (over a total of 94 foraging trips) in 2012 and 2013, using GPS and temperature-depth recorders. Feathers were also collected on all birds to investigate their trophic status. Despite Zembra being the largest seabird colony in the Mediterranean (141,000 pairs), the per capita home-range of Scopoli's Communicated by S. Garthe.

A new algorithm for the identification of dives reveals the foraging ecology of a shallow-diving seabird using accelerometer data

“…Conversely, accelerometers, using only body acceleration, can identify even very shallow dives, where birds might only partially immerse their body into the water, in a very typical way for many Procellariiformes (Ashmole 1971). Dive data from previous studies on Scopoli's shearwater are in line with our results: Grémillet et al (2014Grémillet et al ( ) recorded 9 ± 8 (2012 and 49 ± 47 (2013) dives per trip using TDRs during chick-rearing, while our algorithm recorded 84.7 ± 156.4 dives per trip in the same period. Rubolini et al (2015) recorded an average of 0.35 ± 0.02 dives per hour using compass loggers during chick-rearing.…”

“…Therefore, our algorithm can increase the knowledge of the foraging ecology of other shallow divers. This is an important result, because until now, the identification of shallow dives has always been limited by the pressure and time resolution of TDRs in shallow-diving seabirds (Grémillet et al 2014).…”

“…used in several seabirds (Shaffer et al 2009;Ronconi et al 2010;Paiva et al 2010a;Grémillet et al 2014). However, even high-accuracy TDRs might not be enough to identify feeding events occurring in shallow water or close to the sea surface.…”

“…Indeed, during surface dives, a pressure sensor placed on an animal's back does not come in contact with water, or at least not enough to detect a dive. Given that most dives performed by shallow divers occur in the first meters of the water column (Grémillet et al 2014;Rollingson et al 2014), it is possible that shallow dives might have been underestimated due to the limitation of TDR.…”

“…Fledglings leave their nests from mid to end of October. Scopoli's shearwaters exploit a wide range of prey (Grémillet et al 2014) and forage close to the sea surface (Zotier et al 1999). During incubation, parents perform mainly long trips lasting several days (Cecere et al 2013).…”