Atlantic blue tang - Acanthurus coeruleus - Bloch & J. G. Schneider, 1801 - Cyprus

Unexpected alien species in Cyprus waters

Acanthurus coeruleus is a surgeonfish found commonly in the Atlantic Ocean. It can grow up to 16 inches (41 cm) long. Common names include Atlantic blue tang, blue barber, blue doctor, blue doctorfish, blue tang, blue tang surgeonfish, yellow barber, and yellow doctorfish.
Acanthurus coeruleus is common off the coast of Florida, The Bahamas, and other places in the Caribbean Sea, including Bonaire. Blue Tangs are very common in Belize and especially Ambergris Caye. They are also common in the Gulf of Mexico. They are also found south to Brazil and north to New York.
.Although the body of the reef fish can vary in shade from light to dark blue, the dorsal, anal and caudal fins are golden blue. As juveniles, the edges on their dorsal and anal fins and the rings around their eyes are purple-blue, blue or blue-green. Their colors change during growth from a yellow juvenile, yellow tailed blue subadult and the blue adult phase.

Atlantic blue tangs inhabit coral reefs and inshore grassy and rocky areas, where there is a high prevalence of algae. They are herbivorous, and their diet consists only of algae. They eat the algae from the reefs in which they reside, as well as off the bodies of surrounding fish. By eating the algae off of other fish, the blue tang serve as cleaners for them. With the decline in the Diadema antillarum (sea urchin) population, the blue tang population increased since the algal resources that the two animals usually competed for were more abundant.

Juvenile blue tangs eat continuously and feed heavily. This heavy feeding requirement is due to their poor utilization of food resources. The blue tang's stomach and intestinal lining are proficient at absorbing crushed cellular content, but are not very effective at processing cellulose. This digestive system inefficiency leads blue tangs to spend more time and resources on foraging on a very abundant and fast-growing food source in close proximity. This close proximity to an abundant food source allows for continuous foraging.

Food distribution, density, and accessibility can determine population density and territory size in blue tangs. Territories with low biogenic structure are larger than those of higher biogenic structure. Since the algal food resources are less dense in low-biogenic structured areas, these territories would have to be larger in order to include the necessary amount of food. This is in accordance with the Ideal free distribution model. This model states that competitors should adjust their distribution in accordance with habitat quality such that each individual will gain the same amount of resources.

According to this model, there should be a lower density of blue tangs on low-biogenic structured territories compared to higher-biogenic structured territories where there is a higher abundance of food. In both territories, each individual will receive similar amounts of resources due to competition. There is no significant difference in feeding rates of blue tangs on each type of territory, meaning that those in larger, uncolonized, and low density territories can match the resources of those in smaller high density territories.Από τη Βικιπαίδεια, την ελεύθερη εγκυκλοπαίδεια

Photos and video Mandria, Akrotiri Gata and Akrotiri Zevgari  by Kostas Aristeidou

Marine Biodiversity Records, page 1 of 3. # Marine Biological Association of the United Kingdom, 2012 doi:10.1017/S1755267212001042; Vol. 5; e116; 2012 Published online

Unexpected alien species in Cyprus waters: Acanthurus coeruleus (Actinopterygii: Acanthuridae)

joachim langeneck1 , massimiliano marcelli2 and helmut carl simak3

1 Universita` di Pisa, Dipartimento di Biologia, Unita` di Biologia Marina e Ecologia, Via Derna 1, I-56126 Pisa, Italy, 2 Universita` di Roma ‘La Sapienza’, Dipartimento di Biologia e Biotecnologie ‘Charles Darwin’, Piazzale Aldo Moro, 9–00185, Rome, Italy, 3 Waidmannsforferstrasse 16/7 A-9020 Klagenfurt, 

Austria In December 2011 a specimen of the blue tang surgeonfish Acanthurus coeruleus was observed in the waters of Cyprus. As this species typically lives in the tropical western Atlantic Ocean, its presence in the Mediterranean Sea is very likely to be related to human activities. Speculated ways of introduction in the Mediterranean Sea are discussed. 

Keywords: alien species, blue tang surgeonfish, Acanthurus coeruleus, climatic changes Submitted 30 September 2012; accepted 25 October 2012

INTRODUCTION

 Among the family Acanthuridae only one species has been recorded from the Mediterranean Sea so far, namely Acanthurus monroviae Steindachner, 1876, which was reported first from southern Spain (Crespo et al., 1987) and later from Israel’s Mediterranean coast (Golani & Sonin, 1996). In the years 2001–2002 it was observed quite regularly along the Algerian coast (Hemida et al., 2004). Here we report the first occurrence of the blue tang surgeonfish Acanthurus coeruleus Bloch & Schneider, 1801 in the Mediterranean Sea and some ways the species may have been introduced are discussed.

MATERIALS AND METHODS

 On 1 December 2011, during a SCUBA dive in the vicinity of Xilofagou (south-eastern Cyprus: 34857′ 41′′N 33849′ 48′′E), a single juvenile specimen of Acanthurus coeruleus (Figure 1) was observed, and several photographs were taken. The specimen (approximately 8 cm total length) showed up at a depth of 4–5 m over rocky bottom covered by calcareous algae among some individuals of Thalassoma pavo (Linnaeus, 1758), Sparisoma cretense (Linnaeus, 1758), Chromis chromis (Linnaeus, 1758) and Sargocentron rubrum (Forsska˚l, 1775). The morphological characters match those of a juvenile specimen of A. coeruleus: although many surgeonfishes have yellow juvenile phases, only A. coeruleus and Acanthurus pyroferus Kittlitz, 1834 show electric blue fin edges and a blue ring around both eyes (Lieske & Myers, 1995). However, the two species can be easily distinguished, as A. coeruleus shows 9 dorsal spines, whereas A. pyroferus

shows only 8. As the observed specimen has 9 dorsal spines it should be clearly identified as A. coeruleus. A second observation of a conspecific specimen took place two days later on the 3 December 2011 near Ayia Napa, about 12 km from the first sighting (34859′ 11′′N 33857′ 53′′E). Although the photographs taken at this time are not so clear, the fish in the photograph appears to be A. coeruleus as well.

DISCUSSION

 Acanthurus coeruleus usually lives in the western Atlantic Ocean, mainly in tropical waters; it has been recorded from islands of the Mid-Atlantic Ridge too, especially from Ascension Island (Cadenat & Marchal, 1963; Lubbock, 1980). The present record reports for the first time the presence of this species in the Mediterranean Sea; it is not clear whether the specimen observed on the 3 December is the same as the one observed on the 1 December 2011. The presence of at least one juvenile specimen in the Mediterranean Sea could be explained by three processes: (i) arrival in the Mediterranean Sea through the Atlantic Ocean unrelated to human activities; (ii) introduction by shipping of eggs or larvae; and (iii) release of a captive specimen. The establishment of a tropical Atlantic fish first in the eastern Mediterranean, and its subsequent westward spreading, is already known for the fangtooth moray eel Enchelycore anatina (Lowe, 1839) (Ben Tuvia & Golani, 1984; Bitar et al., 2003; Guidetti et al., 2012)—probably due to the warmer waters of the eastern basin; however, this possibility seems to be unlikely for Acanthurus coeruleus because of the huge distance to travel, although the larval phase of this species has a planktonic life span of 45 –70 days (Rocha et al., 2002) which seems to be sufficient for crossing the Atlantic Ocean and the Mediterranean Sea from west to east.

The second possibility is the introduction by shipping within ballast water containing larval and juvenile specimens. This kind of introduction of species with a distribution range very far from the Mediterranean Sea is already known (Rodrı`guez & Sua`rez, 2001; Galil, 2006) for bony fishes (Goren et al., 2009; Schembri et al., 2010); the long pelagic life of the larval stage accords with this hypothesis. The colonization via ballast water is known for western Atlantic species, for example Pinguipes brasilianus (Cuvier & Valenciennes, 1829) (Orsi Relini, 2002) and the hermatypic coral Oculina patagonica De Angelis, 1908 (Zibrowius, 1974; Fine et al., 2001). A likely possibility as well seems to be the escape of a young specimen from captivity, as the species is commonly traded as aquarium fish. This way of introduction in the Mediterranean has been speculated for the exotic fishes Platax teira (Forsska˚l, 1775) (Bilecenoglu & Kaya, 2006) and Pterois miles (Bennett, 1803) (Golani & Sonin, 1992); the latter has been also introduced through aquarium escapees along the western Atlantic Coast, where it is currently considered as a highly invasive species (Morris et al., 2009). However, as these species commonly occur in the Red Sea, an arrival through the Suez Canal cannot be excluded. For a third species, Scatophagus argus (Linnaeus, 1766), whose native range covers the Indian Ocean (excluding the Red Sea) and the Pacific Ocean, the most likely explanation of the presence in the Mediterranean Sea seems to be the aquarium escape (Zammit & Schembri, 2011). Nevertheless, at present, no documented introduction of bony fishes via aquarium trade is known in the Mediterranean. Another two western Atlantic species, namely Paranthias furcifer (Valenciennes, 1828) and Holacanthus ciliaris (Linnaeus, 1758), were recently reported, on the basis of single specimens, from a little bay in the central part of the eastern Adriatic Sea (Dragicˇevic´ & Dulcˇic´, 2012); these authors considered their presence related to the long rest of an oil platform coming from the Gulf of Mexico in a Croatian shipyard. Such an explanation, however, is not plausible for the present record. Apart from the way of introduction, about which only suggestions can be made, Acanthurus coeruleus is a highly thermophilic species; its survival in late autumn in the eastern part of the Mediterranean Sea is remarkable, probably related to the trend of global warming and especially to the warming of the Mediterranean waters (Francour et al., 1994). This record of A. coeruleus in the Mediterranean Sea

is probably an accident: the establishment of this western Atlantic species in the Mediterranean seems unlikely

ACKNOWLEDGEMENTS

 We are very grateful to B. Dragicˇevic´ and J. Dulcˇic´ for providing literature and to the anonymous referees for their valuable comments and corrections.