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

aGrémillet, D., Péron, C., Pons, J.-B., Ouni, R., Authier, M., Thévenet, M. & Fort, J. 2014. Irreplaceable area extends marine conservation hotspot off Tunisia: insights from GPS-tracking Scopoli’s shearwaters from the largest seabird colony in the Mediterranean. Marine Biology 161: 2669-2680.  doi:10.1007/s00227-014-2538-z

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 three-dimensional 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 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.

Ringing and tagging with a GPS mounted on TDR of Scopoli’s Shearwater (Calonectris diomedea), Zembra Archipelago, Tunisia

Ringing and tagging with a GPS mounted on TDR (temperature–depth recorders) of Scopoli’s Shearwater (Calonectris diomedea), Zembra Archipelago, Tunisia (photo: Initiative PIM).

Increase in Yelkouan Shearwater population in Zembretta (Tunisia) following ship rat eradication

Bourgeois, K., Ouni, R., Pascal, M., Dromzée, S., Fourcy, D., & Abiadh, A. (2013). Dramatic increase in the Zembretta Yelkouan shearwater breeding population following ship rat eradication spurs interest in managing a 1500-year old invasion. Biological Invasions 15 (3) : 475-482.   DOI: 10.1007/s10530-013-0419-x

Abstract:

The ship rat (Rattus rattus) was introduced 1,500 years ago to the Zembra Archipelago (Tunisia) and was eradicated in October–November 2009 on two of its islands, Zembretta and Zembrettina. This eradication was performed 2 years after the discovery of a small colony of Yelkouan Shearwaters (Puffinus yelkouan), a species recently up-listed to the vulnerable IUCN extinction risk category. For 2 years before and 3 years after rat eradication, the Zembretta Yelkouan shearwater breeding colony was checked yearly at the end of the breeding season. The number of recorded breeding pairs reaching 176 and 145, respectively, increases of 10.4 and 8.5-fold two and 3 years after rat eradication. This experiment shows that eradication of an ancient introduced ship rat population has dramatically improved the Zembretta Yelkouan Shearwater breeding population very quickly. This result suggests that managing even long-introduced populations might well be fruitful.

Yelkouan Shearwaters (Puffinus yelkouan) ringed and released at the entry of its burrow, Zembra, Tunisia

Yelkouan Shearwaters (Puffinus yelkouan) ringed and released at the entry of its burrow, Zembra, Tunisia (photo: Awatef Abiadh / Initiative PIM)