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Research Article
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First Record of Three Species of Gerreids (Pisces: Perciformes) from the Jaffna Lagoon, Sri Lanka |
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S. Shutharsan
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K. Sivashanthini
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ABSTRACT
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The present investigation is an attempt to record three
species of gerreids for the first time from the Jaffna lagoon, Sri Lanka.
Gerreids are economically important fish found along the coastal regions
of Sri Lanka. Seven species namely Gerres abbreviatus, Gerres
acinaces, Gerres filamentosus, Gerres lucidus, Gerres
oblongus, Gerres oyena and Pentaprion longimanus have
been recorded in Sri Lankan waters. However, only two species of gerreids,
Gerres abbreviatus and Gerres oblongus have been recorded
from the Jaffna lagoon, so far. During the present investigation samples
were collected from Pasaiyoor, Kurunagar, Kakkaiteevu and Ponnalai coastal
areas from commercial catches by siragu valai, hand nets, hook and line
and bottom trawling. The morphometric characters were observed, measured
and examined and three new species of gerreids were recorded. Those are
Gerres filamentosus, Gerres acinaces and Gerres
lucidus. The distinctive features to identify those species and a
key for identification discussed in detail in the present study. The record
of these species is an important contribution to ichthyofauna of Northern
Sri Lanka. The occurrence of these species in the Jaffna lagoon can be
explained that they may have migrated due to the environmental changes
from the Indian ocean.
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INTRODUCTION
Gerreids are economically important food found in the Indo-Pacific region
included under family-Gerreidae. Nelson (1994) listed 40 species belonging
to 8 genera such as Diapterus, Eucinostomus, Eugerres,
Gerres, Paregueila, Pentaprion, Ulaema and
Xystaema in the world waters. Talwar and Kacker (1984) described nine
species (Gerres abbreviatus, G. filamentosus, G. limbatus,
G. macracanthus, G. oblongus, G. oyena, G. poeti,
Gerreomorpha setifer and Pentaprion longimanus) belonging
to 3 genera from Indian waters. Research on diversity of gerreids showed
ten of the twelve species of mojarras found in the western Atlantic Ocean,
to occur regularly in the Indian River Lagoon (Matheson and Gilmore, 1995).
Recently, nine species belonging to 2 genera (Gerres abbreviatus,
G. filamentosus, G. lucidus, G. macracanthus, G.
oblongus, G. oyena, G. acinaeces, G. setifer
and Pentaprion longimanus) have been recorded along the Indian
waters (Anonymous, 2000). Ramaiyan and Senthilkumar (1997) reported 5
species belonging to 2 genera from Parangipettai waters. Sivashanthini
and Subramanian (2003) reported six species of gerreids belonging to two
genera from Parangipettai waters.
Gerreid species from the Indo-Pacific have long been confused taxonomically
because of their similar overall appearance and coloration and similar
counts, necessitating an urgent taxonomic revision of the group (Woodland,
1983; Iwatsuki et al., 1999a). Three species complexes have recently
been erected in the genus Gerres: (1) the G. filamentosus
complex, including G. filamentosus Cuvier, 1825, G. infasciatus
and G. macracanthus Bleeker, 1854 (Iwatsuki et al., 1996;
Iwatsuki and Kimura, 1998); (2) the G. oyena complex, including
G. baconensis (Evermann and Seale, 1907), G. equulus (Temminck
and Schlegel, 1844) and G. oyena (Forsskål, 1775; Iwatsuki
et al., 1999a) and (3) the G. setifer complex, including
G. chrysops Iwatsuki, Kimura and Yoshino, G. decacanthus
(Bleeker, 1865), G. setifer (Hamilton, 1822) and G. silaceus
(Iwatsuki et al., 1999b, 2001).
In Japan, populations of gerreids have been identified genetically using
Random Amplified Polymorphic DNA Techniques (Miyanohara et al.,
1999) so also in identifying the G. oyena populations from Miyazaki
and Okinawa waters. The authors strongly suggested that both populations
were constituted by different species although considered as same species
all along.
While investigating gerreid fishes in Jaffna lagoon, Sri Lanka the authors
recognized three species of gerreids such as Gerres filamentosus,
Gerres acinaces and Gerres lucidus for the first
time. Seven species of Gerreids have been recorded in Sri Lanka, so far.
Those are G. abbreviatus, G. acinaces, G. filamentosus,
G. lucidus, G. oblongus, G. oyena and Pentaprion
longimanus (Anonymous, 1995). However, only two species of gerreids,
G. abbreviatus and G. oblongus have already been recorded,
from the Jaffna lagoon, Sri Lanka (Sivashanthini and Subramanian, 2002),
so far. In the present study, the above mentioned three new species of
Gerreids have been identified.
MATERIALS AND METHODS
Samples were collected from July to December 2007 from the landing centers
such as Pasaiyoor, Kurunagar, Kakkaiteevu and Ponnalai (Fig.
1). Gerres filamentosus was recorded for the first time among
the catches collected from Ponnalai landing center by nets on 19 July
2007. Gerres acinaces collected from the Passaiyoor and Ponnalai
landing centres on 26 July 2007 and 14 August 2007 respectively. Gerres
lucidus was collected from Ponnalai landing centers on 04 December
2007. Counts and measurements generally followed Hubbs and Lagler (1947)
and Woodland (1983, 1986). Institutional codes follow Leviton et al.
(1985). Additional institutional abbreviations are as follows: University
of Jaffna (UOJ), Department of Zoology (ZOO). The macroscopic and morphometric
measurements were taken in laboratory and the sample was then fixed in
10% formalin. The materials preserved in the Zoology laboratory of Jaffna
University with the catalogue numbers,
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Fig. 1: |
Figure showing the collection sites |
G. filamentosus |
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UOJ/ZOO/GF/2007 |
G. acinaces |
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UOJ/ZOO/GA/2007 |
G. lucidus |
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UOJ/ZOO/GL/2007 |
For morphometric identification the following measurements were taken
for those specific new species: Total length, fork length, standard length,
depth, head length, snout length, anterior point of snout to first dorsal
spine, eye diameter, scale count, caudal fin length, body color, level
of pectoral fin, spines and rays of anal, caudal, pelvic, pectoral and
dorsal fins. Length measurements were taken in centimeters with two decimal
place correction by using measuring board and measurement tape. Weight
measured in grams by electric balance with two decimal place correction.
RESULTS AND DISCUSSION
For Gerres filamentosus, second dorsal spine laterally compressed,
produced into a filament, whose tip extends and past the level of first
anal spine. It`s body depth contained 2 to 2.5 times in standard length
in larger specimen, up to 3 times in smaller specimen, mouth small, strongly
protrusible, fine teeth in jaws, second dorsal spine laterally compressed,
produced into a filament, whose tip extends past level of first anal spine
(filament often damaged) greater than head. Third dorsal spine laterally
compressed, as long as distance from tip of snout to preopercular margin,
Pectoral fin long, tip of depressed fin reaching to level of origin of
first anal spine, 2nd anal fin spine much shorter than fin base, Caudal
deeply forked, its longest rays 3 times the length of median rays. Color
silvery, with 7 to 10 columns of ovoid spots on upper portion of sides,
coalescing as bars in small specimens. Body compressed and elevated. Pectoral
fin long, tip of depressed fin reaching to level of origin of first anal
spine. On lateral line 44 to 47 scales. External morphology of G. filamentosus
is shown in Fig. 2.
For Gerres acinaces, 2nd anal spine fairly strong, much longer
than eye diameter. Caudal fin deeply forked and very long, its longest
ray longer than either pectoral fin or head. Scales on lateral line 42
to 44 to base of caudal fin and 3 to 5 more on scaly sheath on caudal
fin base. 4.5 to 5.5 scale rows between lateral line and base of 5th dorsal
spine. Depth contained 2.5 to 2.9 times in standard length. It consist
slender body. Color Olive green above to silver below, columns of dark
ovoid spots below lateral line, as many as 5 spots below highest part
of lateral line. External morphology of G. acinaces is shown in
Fig. 3.
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Fig. 2: |
External morphology of Gerres filamentosus |
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Fig. 3: |
External morphology of Gerres acinaces |
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Fig. 4: |
External morphology of Gerres lucidus |
For Gerres lucidus, 3 row scales between lateral line and 5th
dorsal spine. Length of caudal fin two times of median ray of caudal fin.
Pectoral fin short. Orange color in anterior part of Pelvic and Anal fin.
Dark black color between 2nd to 5th dorsal spines. Depth contained 2.3
to 2.7 times in standard length, Pectoral fin short, tip of depressed
fin reaching to level of anus but not to level of first anal spine, 2nd
anal fin spine strong and shorter than anal fin base. Lateral line scales
33 to 35 to base of caudal fin and 3 more pored scales on scaly sheath
on base of caudal fin, Color silvery, dusky dorsally. Four diffuse, dark
saddles along back, extending down sides to mid line. External morphology
of G. lucidus is shown in Fig. 4.
Several similar studies were held along the world waters by different
researchers. Iwatsuki and Kimura (1998) originally described Gerres
infasciatus (non-banded whipfin mojarra) on the basis of three specimens
collected from Samut Prakan, northern Gulf of Thailand, western Central
Pacific (Iwatsuki and Kimura, 1998). Gerres infasciatus, was characterized
by having the first and second soft dorsal fin ray tips yellow in fresh
specimens. Very recent investigations of Gerres species from the
Indian Ocean resulted in eight examples of G. infasciatus that
were recorded from Chennai, Tamil Nadu, India (Fukuhara et al.,
2006) and it was reported for the first time from Indian Ocean. Compared
to other gerreid species collected from the Indian Ocean, G. infasciatus
could be easily distinguished from the most similar species G.
filamentosus (Iwatsuki et al., 1996).
Chakraborty, A. and Iwatsuki, Y paid two visits to India and confirmed
that G. infasciatus was the most abundant gerreid species in a
number of markets in Chennai (Madras) compared to similar species of the
G. filamentosus complex: G. filamentosus and G. macracanthus.
However, specimens of G. infasciatus were neither collected nor
observed at other localities along the east and west coast of India, including
the vicinity of the Ganges River Mouth (West Bengal), Trivandrum, Mangalore
and Mumbai (Bombay).
In a study, performed by Iwatsuki et al. (2007) Gerres japonicus
Bleeker, 1854 and Gerres subfasciatus Cuvier in Cuvier and Valenciennes,
1830, are redescribed and Gerres akazakii sp. nov. (Japanese endemic),
Gerres ryukyuensis sp. nov. (Okinawa I., Japan) and Gerres shima
sp. nov. (Indo-Malayan region, including the Andaman Sea, Southeast Asia,
Southern China and Taiwan and Ryukyu Is., Japan) are described. Gerres
ovatus Ganther, 1859 and Gerres kapas Bleeker, 1854, are recognized
as junior synonyms of G. subfasciatus and Gerres oyena (Forsskal,
1775), respectively.
Iwatsuki et al. (2001) studied the taxonomic status of Gerres
limbatus Cuvier in Cuvier and Valenciennes, 1830 and G. lucidus
Cuvier in Cuvier and Valenciennes, 1830. The two species were reassessed
as the same species, the latter corresponding to young of the former,
on the basis of examination of their eight syntypes and other comparative
specimens. Distinguishing morphological characters of these species are
also studied clearly. The authors further specified that these species
were recorded from the southern and western coasts of India including
Sri Lanka, the Malay Peninsula, Gulf of Thailand and Indonesia, becoming
rare in occurrence eastward. The Indian species misidentified as Gerres
poieti (sic) by Cuvier in 1830 was described as a new species,
Gerres phaiya, of the Gerres erythrourus species complex by
Iwatsuki and Heemstra (2001).
CONCLUSION
Those three species have been recorded for the first time in the Jaffna
lagoon. There were no previous records in the northern region of Sri Lanka
for these species. Thus the record of these species is an important contribution
to ichthyofauna of Northern Sri Lanka. The occurrence of these species
in the Jaffna lagoon can be explained that they have migrated due to the
environmental changes from the Indian Ocean. Further studies to record
more gerreid species from the northern region of Sri Lanka is very much
essential to have a complete record of diversity of this species.
ACKNOWLEDGMENT
The authors are grateful for the authorities of University of Jaffna
for the financial assistance and facilities provided.
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