ANNALES · Ser. hist. nat. · 30 · 2020 · 2
227
received: 2020-09-28                 DOI 10.19233/ASHN.2020.27
ABUDEFDUF CF. SAXATILIS IN THE SARONIKOS GULF, GREECE: UNAIDED 
INTRODUCTION OR HUMAN AIDED TRANSFER?
Argyro ZENETOS
Hellenic Centre for Marine Research, Institute of Marine Biological Resources and Inland Waters, GR-19013 Anavyssos, Greece
e-mail: zenetos@hcmr.gr 
Anastasia MILIOU
Archipelagos Institute of Marine Conservation, P.O. Box 42, Pythagorio, Samos 83301, Greece
ABSTRACT
One specimen of the sergeant-major fish Abudefduf sp., provisionally named Abudefduf cf. saxatilis (Lin-
naeus, 1758) was observed for the first time in the Saronikos Gulf, Greece in summer 2020. Its distinctive 
characteristics and potential mode of introduction in the Gulf, whether unaided or man induced transfer, are 
discussed. 
Key words: Abudefduf sp., new record, Saronikos Gulf, crypto-expanding species, citizen science 
ABUDEFDUF CF. SAXATILIS NEL GOLFO DI SARONICO IN GRECIA: INTRODUZIONE 
ACCIDENTALE O INTENZIONALE DA PARTE DELL’UOMO?
SINTESI
Un pesce appartenente al genere Abudefduf, provvisoriamente identificato come Abudefduf cf. saxatilis 
(Linnaeus, 1758) è stato osservato per la prima volta nel Golfo di Saronico, in Grecia, nell’estate del 2020. 
Nell’articolo vengono discusse le caratteristiche distintive dell’esemplare e la potenziale via di introduzione nel 
Golfo, sia accidentale che intenzionale da parte dell’uomo.
Parole chiave: Abudefduf sp., nuova segnalazione, Golfo di Saronico, specie in cripto-espansione, citizen science
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Argyro ZENETOS & Anastasia MILIOU: ABUDEFDUF CF. SAXATILIS IN THE SARONIKOS GULF, GREECE: UNAIDED INTRODUCTION OR HUMAN AIDED TRANSFER?, 227–230
INTRODUCTION
The Saronikos Gulf is a hot spot for alien species 
in Greek waters (Zenetos et al., 2018) with many spe-
cies introduced by vessels. Of the seven introduced 
species of the family Pomacentridae reported in the 
Mediterranean (Osca et al., 2020), only two species 
of the genus Abudefduf are known from Greek waters 
to date. These are: Abudefduf sexfasciatus (Lacepède, 
1801) reported from the Saronikos Gulf (Aegean 
Sea) (Giovos et al., 2018), and Abudefduf vaigiensis 
(Quoy & Gaimard, 1825) reported from Kythira island 
(Ionian Sea) (Pirkenseer, 2020). Here we report on the 
presence of an alleged third species and discuss its 
potential mode of introduction.
MATERIAL AND METHODS
A collaboration agreement between the Archi-
pelagos Institute of Marine Conservation (https://
archipelago.gr/en/) and the Ellenic network on Aquatic 
Alien Species (ELNAIS: Zenetos et al., 2015) in raising 
public awareness on marine alien species was initi-
ated in 2015.
As a result, many new records provided by citizen 
scientists have filled in distribution gaps for some of 
the most invasive species in Greek waters or added 
new records in Greek waters (Miliou & Loudaros in 
Ragkousis et al., 2020). Here we report on one new 
record provided by a citizen scientist (Ms. Mairi D. 
Aga) in September 2020. The report was accompanied 
by 2 photographs. Identification of the species was 
confirmed by the ELNAIS expert Maria Corsini-Foka.
RESULTS AND DISCUSSION
On August 23rd 2020, a single specimen of Abu-
defduf was photographed along the south coast of Sa-
lamina island (Lat 37.877240, Long. 23.442463) at 2 
m depth, during a snorkeling session. The species was 
tentatively identified as A. saxatilis (Linnaeus, 1758).
Abudefduf saxatilis is a tropical and subtropical 
fish of Atlantic origin that has become a commonly 
encountered species along the Israel coasts (Tsadok 
et al., 2015). The first occurrence of A. saxatilis in 
the Mediterranean Sea was reported by Azzurro et 
al. (2013) from Spain. Subsequent records are from 
Malta (Deidun & Castriota, 2014; Vella et al., 2016); 
Turkey (Bilecenoglu, 2016); Israel (Tsadok et al., 
2015) Italy (Lipej et al., 2019); Slovenia (Lipej et al., 
2019); and Libya (Osca et al., 2019). For a detailed 
account of their Mediterranean distribution, see 
Lipej et al. (2019).
Abudefduf saxatilis has been confused in the past 
with A. vaigiensis. The meristic counts and morpho-
metric parameters of two species overlap a lot. As 
illustrated in Lipej et al. (2019) Abudefduf saxatilis is 
morphologically distinguished from A. vaigiensis by 
the following characteristics:
a. in A. saxatilis, the origin of the 4th vertical bar 
is located under the last dorsal spine, while in 
A. vaigiensis it is placed behind the spine in 
the soft part of the dorsal fin;
b. the continuous extension of the fifth dark verti-
cal bar from the origin of the dorsal fin to the 
anal fin in A. saxatilis, which is shorter and 
Fig. 1: Abudefduf cf. saxatilis from Salamina Island. The arrow indicates the two black spots that are the 
distinguishing features of the species (Photo credit: Mairi D. Aga).
Sl. 1: Abudefduf cf. saxatilis iz otoka Salamina. Puščica označuje dve črni piki na repnem korenu, po katerem 
lahko to vrsto prepoznamo (Foto: Mairi D. Aga).
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discontinued in A. vaigiensis and is located on 
the caudal peduncle;
c. the presence of two black spots on the caudal 
peduncle (Fig. 1), which are absent in A. vai-
giensis.
However, some researchers go as far as doubting 
the presence of consistent meristic or morphometric 
differences (see Deidun & Castriota, 2014; Osca et al., 
2019) and, therefore molecular analysis is needed to 
confirm the correct identification of the species. In the 
absence of concrete data (only photographic evidence 
is available) we have provisionally named our finding 
Abudefduf cf. saxatilis (Linnaeus, 1758).
The presence of Abudefduf cf. saxatilis in the Sa-
ronikos Gulf cannot be attributed with certainty to any 
particular pathway because many potential pathways/
vectors could be implicated (range expansion, ves-
sel transfer, release from an aquarium). Considering 
that the closest record is that of Çandarlı bay, Turkey, 
east Aegean Sea (Bilecenoglu, 2016), and that other 
alien fishes attributed to aquaria releases have been 
recorded recently from the Saronikos area (Giovos 
et al., 2018; Karachle et al. in Bariche et al., 2020), 
the most plausible explanation is that of release from 
an aquarium. This is the first record of the species in 
Greek waters. If its occurrence is due to ship transfer 
or to an aquarium release (pathways questioned by 
Lipej et al., 2019), it should be considered a new 
alien species for the area. Evans et al. (2020) classify 
A. saxatilis as a range expanding species (unaided 
introduction via the Gibraltar Strait, since there are at 
least three records which show an eastward progres-
sion in the Mediterranean). We provisionally classify 
it as crypto-expanding until molecular phylogenetic 
analysis shed more light. 
In case it proves to be a man-induced transfer, 
it will be added to the list of alien species in the 
Mediterranean, which according to the latest up-
date includes 666 established species (Zenetos & 
Galanidi, 2020).
This is yet another case evidencing the potential 
of citizen scientists to revealing the undetected as 
highlighted by Azzurro et al. (2013), who reported 
the first finding of A. saxatilis from Spain.
ACKNOWLEDGEMENTS
We wish to thank Ms. Mairi D. Aga for provid-
ing the information and photographs, and Maria 
Corsini-Foka for confirming the species identifica-
tion of the species.
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ABUDEFDUF CF. SAXATILIS V ZALIVU SARONIKOS (GRČIJA): NENAMEREN ALI 
NAMEREN VNOS?
Argyro ZENETOS
Hellenic Centre for Marine Research, Institute of Marine Biological Resources and Inland Waters, GR-19013 Anavyssos, Greece
e-mail: zenetos@hcmr.gr 
Anastasia MILIOU
Archipelagos Institute of Marine Conservation, P.O. Box 42, Pythagorio, Samos 83301, Greece
POVZETEK
Primerek seržanta Abudefduf sp., ki sta ga avtorici provizorično poimenovali kot Abudefduf cf. saxatilis (Linnaeus, 
1758), je bil poleti 2020 prvič opažen v zalivu Saronikos (Grčija). Avtorici razpravljata o razlikovalnih znakih in 
možnem načinu prihoda te vrste v zaliv v smislu namernega (antropogenega) ali nenamernega vnosa. 
Ključne besede: Abudefduf sp., novi zapis o pojavljanju, zaliv Saronikos, prikrito razširjajoča se vrsta, ljubiteljska znanost 
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