New Marine IBAs For the Mediterranean ShagPhalacrocorax Aristotelis Desmarestiiin Slovenia

Abstract

The IBA network is being regularly updated, based on new data and their better quality. There have been three previous stages of the marine IBA identification in Slovenia and the Mediterranean Shag has been included as the qualifying species only in the most recent stage in 2011. However, the sites were limited to inshore coastal roost-sites and thus insufficient to cover the foraging areas of the species. To fill this gap in the Slovenian territorial sea, new marine IBAs have been identified for the Mediterranean Shag within the scope of the SIMARINE-NATURA (LIFE10NAT/SI/141) project in the 2011–2015 period. The new sites were identified following standardized methodology for the identification of marine IBAs from BirdLife International. The data on the Mediterranean Shag distribution and population size were collected using four field methods: (1) monthly monitoring at in-shore communal roost-sites, (2) monthly monitoring at sea following the standardized ESAS method, (3) GPS telemetry, and (4) unsystematic census of in-shore floating groups. Based on these data, one new site, the IBA Osrednji Tržaški zaliv, and one extension to the existing IBA Debeli rtič were identified, covering 8,218 ha and 155 ha, respectively. The new sites cover 39.2% of the Slovenian territorial sea.

Conservation Status of the Mediterranean Shag Gulosus aristotelis desmarestii in the Adriatic Sea during the Non-Breeding Period: Baseline Population, Trends, Threats and Knowledge Gaps

“…To assess the baseline population size of the Adriatic population, a coordinated census by c. 50 expert volunteers was organised to carry out surveys between the 15 th and 22 nd of July 2020 and 2021 across all known major roosting sites in NE Italy, Slovenia and Croatia. According to previous research (Koce, 2018; Scridel et al, 2020a), this period is the time of peak shag of abundance in the northern Adriatic during the non-breeding season.…”

“…It might be possible that birds migrating to the Gulf of Trieste have lower survival than in the Venice Lagoon, due to different environmental conditions (i.e., salinity, depth, nutrients, prey availability, etc.). At the same time, GPS-tracking devices can be particularly useful in providing high quality spatial and temporal information on the foraging behaviour of this coastal seabird, assessing potential effects of water depth, salinity, nutrients and temperature on energetics, during both the breeding and non-breeding periods (Evans et al ., 2015; Koce, 2018). However, there are significant challenges and limitations that need to be carefully addressed when utilising GPS devices on diving species during the non-breeding period.…”

“…These encompass evaluating the potential impacts of GPS harnesses on diving behaviour and addressing the logistical complexities associated with recapturing birds outside the breeding season. Previous research from the SIMARINE-NATURA LIFE project (LIFE 10NAT/SI/141) in Slovenian waters has laid a solid foundation for future investigations by successfully capturing shags using clap-net traps equipped with remote triggering (Koce, 2018). These traps are mounted on floating objects, such as mussel farm buoys, which shags commonly use for resting or roosting.…”

“…Protection measures should extend beyond the immediate surroundings of the breeding sites and be enforced throughout the main non-breeding areas of the northern Adriatic. While significant progress has been made in including the majority of shag roosting sites in Slovenia within the Natura 2000 network, the designation of foraging areas is still ongoing (Koce, 2018). In contrast, in Italy, protection measures only partially overlap with both roosting and foraging sites.…”

“…In the northern Adriatic, depletion of fish stocks around the Croatian breeding colonies is believed to have triggered a new migratory habit, causing shags to move to the shallower and food-rich waters of the Gulf of Trieste and Venice Lagoon located up to a few hundred kilometers away from their breeding colonies (Sponza et al , 2010, 2013; Cosolo et al, 2011; Lipej et al , 2016). These non-breeding movements within the Adriatic started in the 1980s and since then they have increased consistently over time, peaking around 2011-2012 with figures ranging from 6,000 to 10,000 individuals (Škornik et al , 2011) and coinciding with the availability of so-called “ biventia ” longline mussel farms that have served as suitable undisturbed roost sites along the otherwise densely-populated coasts of the Gulf of Trieste (Bordjan et al , 2013; Koce, 2018; Scridel et al , 2020a).…”