MARINE MAMMAL SCIENCE, (MONTH 2018)
© 2018 SOCIETY FOR MARINE MAMMALOGY
Stranding patterns of the striped dolphin (Stenella
coeruleoalba, Meyen 1833, Delphinidae) along the Sicilian
coast (Mediterranean Sea)
SANTO CARACAPPA,ROBERTO PULEIO,GUIDO RUGGERO LORIA,ANTONINO GENTILE,
MARIA FLAMINIA PERSICHETTI,GIULIA CARACAPPA and FRANCESCA LICITRA,
Istituto Zooproﬁlattico Sperimentale della Sicilia, Via G. Marinuzzi, 3, 90129
Palermo, Italy; MARCO ARCULEO,
Università di Palermo, Dipartimento
STEBICEF, Via Archiraﬁ, 18, 90123 Palermo, Italy.
The aims of the Marine Strategy Framework Directive (MSFD -
2008/56/EC) are to “attain good environmental status”of the marine
waters managed by each EU member state by 2020. Marine mammals
are included in Annex III of the MSFD. Thus, assessing the status and
furthering our knowledge regarding all marine mammal species in the
region is important to this effort. All cetacean species present in the
Mediterranean Sea are included in Annex III but knowledge about many
species is incomplete (Notarbartolo di Sciara 2002).
One of the main causes of cetacean deaths in the Mediterranean Sea is
bycatch, due to the accidental ingestion of hooks and lines from long-
lines or entanglement in ﬁshing nets (trawl nets, trammel nets, gill nets)
(Bearzi 2002, Goetz et al. 2014). Of the various ﬁshing nets, gill nets are
probably the most harmful (Read et al. 2006). Other causes of marine
mammal deaths in the region include the ingestion of plastic, airgun
blasts, and high levels of pollutants (Marsili et al. 1997, Fossi et al. 2004,
Baulch and Perry 2014, Castellote and Llorens 2016).
The striped dolphin (Stenella coeruleoalba, Meyen 1833) is one of the
most abundant species in the Mediterranean Sea and occurs in its high-
est density in the western Mediterranean region where the Gulf of Lyon
Corresponding author (e-mail: firstname.lastname@example.org).
and the Pelagos Sanctuary are located (Carlucci et al. 2016). The Medi-
terranean Sea subpopulation is listed as “vulnerable”on the Interna-
tional Union for Conservation of Nature’s Red List (IUCN 2012 http://
www.iucnredlist.org/details/16674437/0). Until now, there has been
only limited data regarding the strandings of the Mediterranean striped
dolphin, and much of it has been reported in an Italian database (http://
mammiferimarini.unipv.it). This database is an important source of
information with which to address the potential causes of death of
striped dolphins and the spatio-temporal ﬂuctuations in stranding pat-
terns. For example, the 2013 and 2016 records show a marked increase
in striped dolphin strandings along the Italian coast due to a morbillivi-
rus epidemic (Giorda et al. 2017). However, causes of death are typically
unexplained because necropsies are often unable to detect particular
pathologies or the contributory factors are unknown.
Building on what is known from the Italian database, the aim of this
study was to examine the biological data collected from striped dolphin,
stranded along the Sicilian coasts for the period 2013 to 2016. These
data were compared to those found in the literature in order to identify
possible management implications for the species and the ﬁshing activi-
ties taking place in these areas.
Along the coasts of Sicily, 73 striped dolphins strandings were
recorded from 2013 to 2016. The specimens were collected at the Centro
di Monitoraggio e Controllo per Tartarughe marine e Cetacei [Monitor-
ing and Control Centre for Marine Turtles and Cetaceans] at the Istituto
Zooproﬁlattico Sperimentale della Sicilia. Subsequent necropsies were
performed to determine the cause of death. The date and stranding loca-
tion were recorded for each specimen. Total body length, weight, sex,
and other key biometric measurements were also recorded for fresh and
moderately decomposed specimens, in accordance with Geraci and
Lounsbury (2005). Following Carlini et al. (2014) and references therein,
the individuals were divided into three life stage categories on the basis
of total body length: (1) newborns <100 cm, (2) juveniles from 100 cm
to 190 cm, and (3) adults >191 cm.
Finally, stranding data were grouped according to Mediterranean geo-
graphical subareas (GSAs), as identiﬁed for the Italian seas by the GFCM
(General Fisheries Commission for the Mediterranean Resolution
31/2007/2), which are used to manage ﬁsheries. The Mediterranean Sea
is recognized as one of the world’s more than 60 great marine ecosys-
tems and is divided into 30 GSAs of different sizes and characteristics.
According to these, Sicily’s coastline falls into GSA 10 (central and low
Tyrrhenian), GSA 16 (central Mediterranean), and GSA19 (Ionian Sea)
(Fig. 1). This subdivision is also used to facilitate decisions in different
GSAs to reduce the possible impact of ﬁshing activities on cetaceans,
which are subject to speciﬁc regulations.
Most specimens were collected during the summer and autumn sea-
sons. All specimens came from the three Mediterranean GSAs: 18 from
GSA 10, 8 from GSA 16, and 47 from GSA 19 (Fig. 1). The numbers of
individuals stranded during 2013 (n= 22) and 2016 (n= 23) was higher
than those in 2014 (n= 17) and 2015 (n= 11) (Table 1; Fig. 2).
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An external body examination of the stranded specimens revealed
signs of injuries for only four individuals (5.4% of the total sample), and
this may be attributable to accidental catch by drift nets or gill nets. This
low percentage would suggest that the majority of deaths are unrelated
to ﬁshing activities. The condition of the specimens, referring to their
state of decomposition (Geraci and Lounsbury 2005), showed that most
individuals were in Code 3 (38.3%) and Code 2 (30.1%). Necropsy exam-
inations performed on all individuals (73) identiﬁed 30 males and
28 females. Of the remaining 15 specimens, it was not possible to iden-
tify their sex due to the advanced state of general and gonad deteriora-
tion or the young age of individuals (Fig. 3). The sex ratio of all
specimens analyzed (juvenile and adults) was 1.07M:1F. Of note, nec-
ropsy did not reveal any pregnant females or the presence of plastic
bags, hooks, or ﬁshing line in the internal organs.
The minimum and maximum total lengths (TL) of stranded dolphins
were 91 and 207 cm for females and 84 and 243 cm for males, respec-
tively (Fig. 4).
Taking into account the sizes and the sexes of the few individuals
available and according to other authors (Notarbartolo di Sciara and
Demma 1994, Marsili et al. 1997, Carlini et al. 2014), 13 females, 5 males,
and 5 of indeterminate sex had a total length (TL) >190 cm, the typical
size of adult individuals. 11 dolphins were <100 cm, corresponding to
newborn animals, which were only a few days old, with 39 specimens
measuring between 101 cm and 190 cm (Fig. 4). Adults comprised
Figure 1. Map of striped dolphin strandings along the Sicilian coasts. Sicily with
the Mediterranean geographical subareas. GSAs Source: http://www.fao.org/
Table 1. Summary of data of strandings of Stenella coeruleoalba along the
Sicilian coasts (2013–2016).
(kg) Sex GSAs
2013 2 202 80.5 F 19
4 172 41 M 19
3 202 130 M 19
3 178 58 F 16
3 243 120 M 10
2 195 47.5 F 19
3 196 72.5 F 10
5 156 30 M 16
3 144 26 M 19
3 116 6 M 19
4 163 68 F 19
5 155 29 M 19
3 124 15 M 10
3 184 57.5 M 19
4 130 24 M 19
3 190 50.5 M 19
3 144 23 M 19
2014 3 133 19 M 16
4 210 74 F 10
5 200 48 M 19
5 161 36 M 19
3 210 63.5 M 19
4 162 42 —10
2 90 7.5 M 19
4 188 52 —19
2 216 68 M 19
4 120 14.5 M 10
4 118 13 M 16
5 110 17 —19
4 100 8.5 —19
2 195 78 F 10
2015 2 203 89 —19
2 206 72 F 19
3 111 13.5 F 10
2 179 42 M 10
2 199 90 F 19
3 106 8 M 10
4 163 35 M 10
3 133 28 —19
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31.9% of the sample, thereby highlighting a greater prevalence of
young/immature individuals in the sample under investigation. A low
presence (15.1%) of stranded newborn (TL < 100 cm) striped dolphins
was also observed.
The numbers of individuals stranded during 2013 (n= 22) and 2016
(n= 23) were higher than those in 2014 and 2015, and in general, than
those reported in other region of the Italian coasts (http://
mammiferimarini.unipv.it) (Fig. 2). According to Casalone et al. (2014),
Giorda et al. (2017), Pintore et al. (2018), and Puleio et al. (2018), it
seems that the high number of stranded specimens during 2013 and
2016 in Sicilian and Italian waters (Fig. 2) was probably caused by Mor-
billivirus epidemics. This was evidenced by histopathological assays,
although other causes of mortality could not be ruled out. Moreover, the
presence of this high number of individuals in GSA 19 was possibly con-
nected to: (1) particular oceanographic conditions (current circulation)
that carried the weakened or already dead specimens from more eastern
areas (Sciacca et al. 2015) and (2) the presence of high sources of
Table 1. Continued
(kg) Sex GSAs
2 121 17.5 F 10
2 84 4.9 M 10
3 155 29.9 F 19
2016 2 175 68 M 16
3 163 45 F 19
3 200 70 F 19
3 164 46 F 10
3 145 26 F 19
3 188 58 F 19
4 135 35.5 M 10
3 125 25 M 19
3 202 75 M 16
2 169 43.5 F 16
2 207 80 F 19
2 98 14.5 F 19
3 133 18 F 19
3 192 64 F 19
4 111 12.5 —19
2 205 82 F 19
4 169 32.5 M 19
4 107 9 M 19
3 190 10.5 —19
4 187 59.5 M 19
2 198 69 F 10
Carcass condition according to Geraci and Lounsbury 2005.
Geographical subareas (GSAs).
disturbance (acoustic and chemical pollution), which could negatively
inﬂuence the survival of this species. The latter seems more likely, con-
sidering the presence of one of the largest oil reﬁneries in Italy along
the eastern coast of Sicily (GSA 19). Skin biopsies of striped dolphins
sampled from different areas of the Mediterranean Sea (GSA 19 included)
Figure 2. Number of individuals stranded during the period 2013–16 along
the Italian and Sicilian coasts. Data relating to Italy was obtained from http://
Figure 3. Number of individuals per sex and years recorded in the three
GSAs (10, 16, 19).
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provided evidence of environmental pollutants such as PCBs, DDTs, etc.
(Panti et al. 2011).
It is also known that pollutants reduce immune defenses, thereby
increasing the chances of contracting various kinds of infections (Fossi
et al. 2004). Acoustic pollution could potentially derive from the inten-
sive trafﬁc of commercial ships and/or airgun blasts. In the former case,
Sciacca et al. (2015) have highlighted the very high background noise
level in the main frequency band of ﬁn whale communication, while in
the latter case, the Ionian Sea and an extensive area off the coast of
Greece have had the highest concentration of seismic exploration activ-
ity in the previous 10 yr period (Maglio 2016). Moreover, according to
Sciacca et al. (2015), the GSA 19 also represents an important feeding
ground for cetaceans. Despite these possible explanations for strand-
ings, to date it has been very difﬁcult to obtain actual data from the
Finally, considering the low number of individuals stranded in the two
other GSAs and the fact that only a small percentage of individuals
revealed injuries due to ﬁshing gear would suggest that the majority of
deaths are unrelated to ﬁshing activities. Indeed, it can be hypothesized
that the concept of GSAs is of limited use to this research and, therefore,
not easily applicable to these studies. Moreover, the habits of the striped
dolphin species must also be taken into consideration: unlike other dol-
phins living in the Mediterranean Sea, the striped dolphin has fewer
coastal habitats, preferring to inhabit areas several miles off the coast.
This could suggest reduced interaction with ﬁshing activities and recrea-
Figure 4. Total length and number of individuals stranded in the three GSAs
(10, 16, 19) for 2013–2016.
The maximum TL of individuals in this study was higher than those
observed by Calzada et al. (1997) in the western Mediterranean but it is
similar to those observed by Carlini et al. (2014) in the north-central Tyr-
rhenian Sea. Moreover, our data conﬁrmed that adults were represented
by approximately one third of the sample, while the remaining part is
made up of young/immature individuals. Particular attention should be
paid to the stranded newborns, probably still nursing. Their stranding
can often be caused by prolonged separation from the mother due to
bad sea conditions, the presence of morbillivirus (as previously indi-
cated in 2013 and 2016), or other causes hitherto unknown.
Our data for stranded striped dolphins along the Sicilian coast and
data reported in the literature are insufﬁcient to ascertain the real causes
of deaths of striped dolphins in the Mediterranean Sea more broadly.
Thus, further study on a larger scale (areas and specimens) is needed to
highlight the need for better data and diagnostic approaches. Moreover,
it is also of primary importance that cetacean monitoring centers liaise
with each other and that they are adequately supported ﬁnancially by
local administrations and ministries.
The authors are grateful to Valeria Vitale Badaco and Daniela Crucitti (IZS
Sicily) for their assistant with the ﬁeld and laboratory work. The authors are
grateful to reviewers who provided valuable suggestions and comments during
revision of the manuscript. This work was supported by the Zooproﬁlattico
Institute of Sicily (Italy).
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Received: 17 January 2018
Accepted: 21 October 2018