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OCCUREENCE, FOOD NATURE, AGE AND GROWTH OF
ORBICULATE BATFISH Platax orbicularis (EPHIPPIDAE) IN IRAQI
TERRITORIAL MARINE WATERS
Amjed K. Resen
Department of Fisheries and Marine Resources, College of Agriculture University of Basrah,
Basrah, Iraq
( Received 19 September 2016,Accepted 27 September 2016)
Keywords; Arabian Gulf, batfishes, omnivore.
ABSTRACT
A total of 313 Orbiculate batfishes Platax orbicularis were studied from the Iraqi marine waters
at the shallow tip of the Arabian Gulf during the period from March to September 2015. This
species is an omnivore (planktivorous) which migrate between surface and bottom for feeding
activity. Length –Weight relationship and growth rate were calculated for the 222 specimens.
The highest growth rate calculated was 5.16 which occurred at length group 23-27cm
equivalent to age group I+. The Iraqi marine waters were indicated as feeding ground but not
spawning ground.
INTRODUCTION
Iraqi marine waters at the most north-western part of the Arabian Gulf are characterized by
high fish diversity where 512 species belonging to 58 families were recorded as (1)
demonstrated the presence of 16 cartilaginous species and 109 bony fishes species.
The family Ephippidae encompasses eight fish genera with sixteen species. Among this
family, several types of protective mimicry are shared by some genera; Platax orbicularis, P.
teira and P. boersii in the Indo-Pacific and Chaetodipteru sfaber in the Atlantic. The orbicular
batfish P. orbicularis also has a broad distribution. It is found throughout the Indo-Pacific
systems, from the Red Sea and East Africa, northwards to the Tuamoto Islands, southern Japan,
and southwards to northern Australia and New Caledonia, and is also associated with coastal
environments such as reefs and mangroves (2).
In the Arabian Gulf, two species i.e. P. teira and P. orbicularis have been recorded
previously (3) with apparent juvenile cryptic mimesis, resembling and behaving like dry leaves
near the water surface( 4). Although some studies have analyzed the feeding and social ecology
of these species, including aspects of mimetic behavior, there is no particular study focusing on
their allometric growth patterns nor their biology in the Arabian Gulf area. It is important to
consider allometric growth data as both species suffer changes in shape, behavior and habitat use
at specific growth phases (2; 5; 4; 6; 7). P. orbicularis was explored to assess growth tendencies
during the transition of the species between mimetic and non-mimetic life stages. The
differences in morphology of juveniles and adult attracted scientists to further investigation the
interested shift in body shape and diet from juveniles to adults. The juveniles occurred near the
surface while the adults live in more deeper layers (5).
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The Orbiculate batfish is a species which has only recently been grown in aquaculture. This
species is reared in Taiwan and Polynesia and also produced on a small scale in Thailand for the
ornamental market. More scientific literatures was traced concerning the food nature of
juveniles of batfish (Barros et al., 2008), beside further concerned about the transition from
pelagic to benthic while other researches dealt with dietary and shape changing from juveniles to
adults (7).
MATERIALS AND METHODS
Fish samples were collected from the Iraqi marine waters at the north-west part of the
Arabian Gulf (E 48˚. 45̀- 48˚.50̀) (N 29˚.48̀-29˚.45̀) (Fig. 1) during the period extended from
March to September 2015 by using trawl nets. A total of 313 fish were collected and examined.
Measurements of total length (TL) and total weight (W) were taken for all fishes. The digestive
tracts of 180 fish were examined for food contents.
Fig. (1): Map of sampling orbicular batfish P. orbicularis collected from the Iraqi marine
waters.
The relationship between the total length and weight was calculated according to the
following equation W= a Lb where X axis represented the total length , Y axis represented the
other parameter, a and b are constants calculated from the data set. The equation of (8) was used
to establish the relationship between increasing length with unit of time [(L2- L1)/ (t2-t1)] and
with average length [(L1+ L2)/2] to give a straight line as follow:
K = - b Loo=a/-b
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The values of K and L∞ are measured by using the draft of (9) while the value of to was
measured by the following equation that derived from the above equation: t0 = { ln (L∞ - Lt)+ Kt
– ln L∞ }/ K
For feeding study, digestive tracts were removed and gave a degree of fullness (between 0 and
20) then opened in a Petri dish to count different food items. Frequency of occurrence and point
methods were used to analyze food items (10). Index of relative important (IRI) was calculated
according to the following formula of (11):
IRI = Pw× F
Where Pw is weight percentage of food item and F is its frequency of occurrence.
RESULTS
The distribution of total length frequency for all 313 fishes was shown in figure (2). It
illustrated the existence of 19 length groups with dominant group of 32 cm (15.3% of total fish),
followed by group 34 cm (11.5% of total fish). Total lengths of fishes were ranged from 20 to 56
cm and weight from 623 to 5442 gm.
Fig. (2): Length group frequency of orbicular batfish P. orbicularis from Iraqi marine waters.
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Fig. (3): The relationship between total length and weight of orbicular batfish (slope value 1.933).
Fig. (4): The relationship between increase length and unit of time (K = 0.23 and L∞=70.9) for
orbicular batfish.
The exhibited length groups and numbers of P. orbiculaisr were exploited to apply cohort
analysis technique. Six age groups were showed containing a minimum age of I+ at lengths of
18-23 cm. The oldest age group VI+ encompassed fishes of 53-57 cm lengths (table 1).
Food analysis was demonstrated according to the values of the index relative importance
(IRI). Algae scored the highest percentage (58%). Food composition dominance of batfish is
followed by zooplankton (21.6%) , benthic invertebrates (13.2 %) coming in third rank and
finally digested matter which represented only (5.7 %) of the diet composition as depicted in
figure (5).
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Table (1): Analysis the length of generation for orbicular batfish P. orbicularis.
Fig. (5): Diet composition of orbicular batfish ( index relative importance (IRI) from Iraqi marine
waters.
DISCUSSION.
Occurrence of batfish in Iraqi marine waters seem to be odd, since these waters represent the
estuarine part of the Arabian Gulf beside the area characterized by muddy substratum and
virtually no coral reef exists.
(12) miss recording batfish from the Arabian Gulf because most of their fish samples were
collected from deeper waters. Again, (13) failed to record batfish from Kuwaiti waters. On
contrary, (14) and (15) recorded batfish from the waters of Qatar and Bahrain. (16) mention that
T Ln (N/ Δt)
¯
No. of t1 t2 tΔ
fish
Mean
T.L
L.
Group
18-22 20 45 1.26 1.60 0.34 1.43 4.88
27-23 25 65 1.69 2.06 0.37 1.87 5.16
32-28 30 62 2.16 2.58 0.42 2.37 4.99
37-33 35 19 2.69 3.17 0.48 2.93 3.811
42-38 40 15 3.30 3.86 0.56 3.58 3.28
47-43 45 8 4.0 4.67 0.67 4.33 2.48
52-48 50 5 4.85 5.67 0.82 5.26 1.80
57-53 55 3 5.89 6.96 1.07 6.42 1.030
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this species occurred at eastern coast of Saudi Arabia and United Arab Emirates. It seems that
batfish occurs on the shallow side of the Arabian Gulf, associated with existence of coral reefs.
The existence of medium and large sizes (20 -56 cm) indicated that the Iraqi marine waters
representing a feeding ground and not spawning ground due to the disappearance of juveniles
and small size specimens as younger fish stay at the coral reef and the spawning grounds (2).
The deviation of batfish length-weigh correlation from the generalized formula for other
fishes is due to the body shape which compressed laterally and not the normal fusiform
correlation between the total length and weight (17). Current results which calculated from the
relationship of the total length of the four types of weight values b at this study did not deviate
significantly from the value 3, coincided with values of b. The relationship of length weight may
vary not only between species and even between individuals within the same sex and this is due
mainly to seasonal variations in the growth, development of the gonads, the level of nutrition
and the rate of deposition of fat in the body (18; 19). Younger ages of batfish of age II+ scored
the fastest and higher length increment (5.66) occurred at length group of 23-27 cm followed by
the next length group (28-32) with increment of (4.99). As its well known in fish biology, most
higher and fast increment in length occur at younger age stages (20).
One of the explanations for the occurrence of batfish in Iraqi marine waters could be due to
availability of important plankton food resources as phyto- and zooplankton since the Iraqi
marine waters is characterized by high primary productivity coincides with winter and spring
blooms followed by zooplankton flourishing as suggested previously (21). It seems that batfish
feed near the surface mostly on phytoplankton and to lesser extent on zooplankton and migrate
toward the bottom to supplement their diet with existed invertebrates, since the tip of Gulf is
considered as a very shallow area. Consequently, the batfish could be considered as an
omnivorous fish with a tendency to be planktivorous; a conclusion which also confirmed by (5).
ORBICULATE BATFISH تواجد وطبیعة تغذیة وعمر ونمو اسماک الوطواط
فی المیاه الاقلیمیة البحریة العراقیة Platax orbicularis (EPHIPPIDAE)
امجد کاظم رسن
قسم الاسماک والثروة البحریة ، کلیة الزراعة ، جامعة البصرة، البصرة ،العراق
الخلاصھ
فی ھذة الدراسة من المیاه البحریة الضحلة Orbiculate batfish Platax orbicularis جمعت 313 سمکة
فی الخلیج العربی للفترة من اضھر الى ایلول 2015 . ان ھذا النوع مختلط التغذبة والتی تنشط تغذیتھا من خلال ھجرتھا بین
السطح والفاع. علاقة الطول بالوزن والنمو حسبت ل 222 عینة. کانت الزیادة فی النمو 5.16 التی ضھرت فی مجموعة
27 سم فی العمر النسبی الاول. اتضح ان المیاه البحریة العراقیة منطقة تغذیة ولیس تکاثر لھذة الاسماک. - الطول 23
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