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International Journal of Marine Science 2014, Vol.4, No.59, 1-5
http://ijms.biopublisher.ca
4
Figure 3 Small specimen < 65 mm SL of
Gerres limbatus
from
Froese and Pauly, 2014. Note the four well-defined saddlebacks
3 Remarks
In present study, the four black saddles on the body
were barely discernible on nine of the specimens
whereas in the 60 mm SL individual the four saddles
were clearly visible (as in Figure 3); Almost all of the
meristic and morphometric characters of these
specimens agree with those reported by Iwatsuki et al.
(2001). The pectoral fin length is longer than head
length in the most (nine out of ten) Iraqi specimens
whereas the head length is greater than the pectoral fin
length in Iwatsuki et al. (2001). We considered this
minor difference as being due to intraspecific
variation resulting from differences in geographical
distribution of the species. The two largest specimens
of
G. limbatus
(154 and 163 mm TL) were collected
during March and August 2013 respectively. Both
exceed the largest reported lengths. Woodland (1983)
gave 150 mm TL as maximum size for
G. lucidus
(now
G. limbatus
). Iwatsuki et al. (2001) examined
53 specimens (45.9-111.5 mm SL) as well as the
single specimen (~75.9 mm SL) in Borkenhagen
(2010). Froese and Pauly (2014) listed 150 mm TL as
the maximum size. Hence, two of the specimens
collected from Iraqi waters represent new length
records for
G. limbatus
.
The actual distribution of
G. limbatus
in the Arabian
Gulf is still unknown. Bishop (2003) did not include
G.
limbatus
on his checklist of fishes reported from
Kuwaiti waters. Borkenhagen (2010) collected a
single specimen ~85 km upstream of the mouth of the
Mand River, Iran at a salinity of 2.5 PSU. The two
specimens we collected from the Shatt Al-Arab River
near Hamdan and Abu Al-Khaseeb villages were at
salinities of 1.4 and 2.7 PSU respectively. Woodland
(1983) used
G. lucidus
Cuvier, 1830 as the valid name
and
G. limbatus
as a questionable name under the
former species.
Iwatsuki et al. (2001) resurrected
G. limbatus
as a
valid species leaving
G. lucidus
a junior synonym.
They were able to distinguish it from the "
Gerres
setifer
complex" that occurred within the same area.
They found the distribution of
G. limbatus
was
restricted to the Southern and western coasts of India,
Sri Lanka, the Southern Malay Peninsula, Gulf of
Thailand, and Indonesia. Borkenhagen (2010)
considered the single specimen of
G. limbatus
from
the Mand River, Iran to be unusual since it
occurred >2000 km west of the known area of
distribution. He offered three possible explanations for
the rarity of confirmed records of this species from
Arabian Gulf: (i)
G. limbatus
has been present since
the postglacial re-colonization of the Gulf by marine
fish. However, the low sampling effort in estuaries and
the lower reaches of rivers and the lack of attention to
the identification of smaller fish species collected in
artisanal fisheries could explain the lack of records; (ii)
A recent natural colonization along the northern coast
of the Indian Ocean, which could possibly be
connected to global change; or (iii) the Arabian Gulf is
one of the busiest waterways in the world and ballast
water from ships is a possible, though unlikely, source
of
G. limbatus
larvae or juveniles.
The collection of 10
G. limbatus
individuals, including
eight from marine waters, suggests that this species
could be a winter migrant into the NW Arabian Gulf.
Such migration was also suggested for
G. longirostris
(Lacepède, 1801) (See Ali, 2013). Gratwicke et al.
(2006) found that a number of Caribbean lagoon fish
species, including
G. cinereus
(=
G. longirostris
),
migrated to reef habitats as adults.
In the present study, the smallest specimen (60 mm SL)
of
G. limbatus
was collected in an estuary (Shatt
Al-Arab River) and larger specimens (91-134 mm SL)
were collected in marine waters. Although this is a
small sample size, this finding could possibly suggest
that there is a seasonal migration of this species
between different habitats, as Gratwicke et al. (2006)
reported for
G. cinereus
.
To the best of our knowledge there are few, if any,
fisheries independent studies in the Arabian Gulf, Gulf