ISSN: 0001-5113 ACTA ADRIAT., SHORT COMMUNICATION AADRAY 60 (2): 193 - 198, 2019 New record of the non-indigenous crab Percnon gibbesi (H. Milne Edwards, 1853) from Palagruža archipelago (Adriatic Sea) Jakov DULČIĆ, Branko DRAGIČEVIĆ* and Denis GAŠPAREVIĆ Institute of Oceanography and Fisheries, Šetalište Ivana Meštrovića 63, HR-21000 Split, Croatia *Corresponding author: [email protected] Several individuals of non-indigenous grapsid crab Percnon gibbesi (H. Milne Edwards, 1853) have been observed and photographed in the area of Palagruža archipelago (Adriatic Sea, Croatia). This is additional confirmed record of this species in the Adriatic Sea. It suggests subsequent range expansion of this species and provides further evidence of its establishment in Adriatic waters Key words: Percnon gibbesi, new record, northward spreading, invasive, Adriatic Sea INTRODUCTION Many marine alien species exhibit invasive Linosa (Strait of Sicily) (RELINI et al. 2000) and behaviour which can lead to alterations in has subsequently spread throughout the Medi- ecosystem functioning, biodiversity loss, and terranean Sea (SUARIA et al., 2017). Its mode of negative impact on human activities such as introduction is unclear with proposed mecha- fisheries, tourism and aquaculture (STREFTARIS nisms of introduction such as migration through & ZENETOS, 2006). In the Adriatic Sea, there is Strait of Gibraltar by larval drift or by accidental a significant increase of occurrences of alien releases from the aquarium trade or other ship- marine species during the last decades (ZENE- ping related activities (YOKES & GALIL, 2006). TOS et al. 2010; PEČAREVIĆ et al. 2013). For most of The spreading pattern of the species in the them the geographical range keeps expanding: Mediterranean was reviewed by KATSANEVAKIS this phenomenon could be attributed both to et al. (2011) who also documented its presence in the presence of empty ecological niches and to the Adriatic Sea for the first time (Sazani Island, global warming (LIPEJ et al. 2009). Albania). Subsequently, its presence in the Adri- Sally lightfoot crab Percnon gibbesi is a atic was documented for the Croatian and Italian primarily algivorous crab (PUCCIO et al., 2006) coasts (DULČIĆ & DRAGIČEVIĆ, 2015; UNGARO & of the shallow infra-littoral rocky shores. It is PASTORELLI, 2015). a widely distributed species, its range extend- The present study reports on the subsequent ing from California to Chile, Florida to Brazil, northward range expansion of this species in the and Madeira to the Gulf of Guinea (MANNING Adriatic Sea with evidence of its further estab- & HOLTHUIS, 1981). It was first recorded in the lishment in Adriatic waters. Mediterranean Sea in 1999 from the island of 194 ACTA ADRIATICA, 60 (2): 193 - 198, 2019 MATERIAL AND METHODS km in length. In the following year, only shallow area of Vela Palagruža was investigated. On 18 September 2018, during casual diving activity, a researcher from Institute of Oceanog- RESULTS AND DISCUSSION raphy and Fisheries observed and photographed (Fig. 1a) a crab at 2 m depth on the island of Morphological features and colour of Mala Palagruža (42.389053º N, 16.270035º E; observed individuals were in agreement with Fig 2 – location “d1“). It was observed hiding descriptions of Percnon gibbesi by various between the boulders and in the vicinity of the authors (RELINI et al., 2000; FANELLI & AZZURRO sea anemone Anemonia sp. The individual was 2004; THESSALOU-LEGAKI et al., 2006). Present photographed and identified as Percnon gibbesi. finding indicates northward extension of distri- Following year, on 21th of August 2019, approx. bution of P. gibbesi up to Palagruža Island, area 20 specimens were observed in the similar further north than area of Molunat Bay (Fig 2. habitat and depth, but on a different location - location “b“), where it was previously recorded (42.39070º N, 16.26633º E; Fig. 1b; location in 2014 (DULČIĆ & DRAGIČEVIĆ, 2015). Crabs “d2“ in Fig. 2). Identification was carried out were photographed near the shores of Mala and following description by RELINI et al. (2000). Vela Palagruža Island, which consisted of boul- Upon the first finding, the diver investigated ders, narrow cracks and scattered pebbles with majority of coastline area of both Velika and algal cover. These habitat characteristics agree Mala Palagruža Island (1-2 m depth) approx. 2 with habitat preferences of P. gibbesi for shallow Fig 1. Photos of a specimen of Percnon gibbesi photographed at a location on Mala (a) and Vela (b) Palagruža in summer of 2018 and 2019, respectively. Red arrows indicates individual crabs (photo: Denis Gašparević) Dulčić et al: New records of the non-indigenous crab Percnon gibbesi (H. Milne Edwards, 1853) ... 195 Fig 2. Locations of previously documented occurrences of Percnon gibbesi from the Adriatic Sea (a – Sazani Island (2010); b – Molunat Bay (2014), c – Bari (2014); d – Palagruža archipelago (2018 and 2019)). Right picture shows zoomed area of Palagruža archipelago with locations of occurrence of P. gibbesi in 2018 (d1) and 2019 (d2) rocks with algal cover (THESSALOU-LEGAKI et al. in the middle of the Adriatic Sea, could act as 2006), as also reported by many other authors (e.g. a stepping-stone, aiding its westward (Italian FANELLI & AZZURRO, 2004; DEUDERO et al. 2005; coast) and northward expansion. UNGARO & PAS- RUSSO & VILLANI, 2005; AZZURRO et al., 2011). As TORELLI (2015) already reported on the finding the depths around this island reaches over 100 of Percnon gibbesi from the area of Bari (Italy, meters from all sides, it is plausible to conclude southern Adriatic) and multiple occurrences that the presence of P. gibbesi around the island have been reported for the northern areas of the is a consequence of larval drift and subsequent Ionian Sea (see SUARIA et al., 2017 and references settlement in the area rather than of active therein). Up to date, northernmost occurrences of migration to the area. Another possibility, which P. gibbesi in the Mediterranean Sea has recently cannot be excluded, is its introduction to the been reported by SUARIA et al. (2017) for the Ligu- islands by recreational or fishing vessels, which rian Sea. occasionally visit the area, especially during Percnon gibbesi is considered among the summer months. „worst“ invasive alien species in the Mediter- Our record, together with those reported by ranean Sea (STREFTARIS & ZENETOS, 2006). In the DULČIĆ & DRAGIČEVIĆ (2015) and UNGARO & Adriatic, this species is spreading northwards PASTORELLI (2015), suggests that P. gibbesi is but its impact on the native species occupying spreading in the Adriatic Sea. This could be also the same ecological niche (shallow-water ben- supported by the fact that specimens of P. gib- thic algal grazers) is not yet known and should besi have been also found in the coastal areas of be evaluated through future investigations. the islands Vis (central Adriatic) (A. ŽULJEVIĆ, pers. comm.) and Korčula (at the transition from ACKNOWLEDGEMENTS southern to central Adriatic) (G. DRAGOJEVIĆ, pers. comm). This work has been fully supported by Croa- Given the pace and nature of its spreading, tian Sci ence Foundation (HRZZ) under the pro- we can presume that it is a matter of time until ject IP-2016-06-5251. it reaches areas of Northern Adriatic, although lower temperature regimes in that area may inhibit its subsequent establishment. Addition- ally, Palagruža archipelago, which is situated 196 ACTA ADRIATICA, 60 (2): 193 - 198, 2019 REFERENCES AZZURRO, E, M. MILAZZO, F. MAYNOU, P. ABELLÒ Smithsonian Contributions to Zoology, 306: & T. TEMRAZ. 2011. 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