Age Determination of Archer Fishes (Toxotes jaculatrix and Toxotes chatareus) Inhabiting Malaysian Estuaries
In this study the most common bony structure (scales)
and method was investigated for age determination of archer fishes. A
total of 85 specimens of archer fishes (Toxotes chatareus and Toxotes
jaculatrix) from the estuaries of South Johore, Malaysia were examined
for age. Scale length is linearly proportion (r = 0.816) to standard length
(SL). Relationship between scale length (L) and scale weight (W) can be
expressed by the formula W = 0.0155L2.917. Daily growth rings
and annulus of scales count up demonstrated that the ages of the samples
for both species were mostly 1-2 years and a handful samples of T.
jaculatrix were above 2 years.
There are seven species in the genus Toxotes, commonly referred
to as archer fishes (Allen, 2004). According to Smith (1945), Luling (1955)
and Allen (1978) they live mainly in the brackish water of mangrove-lined
estuaries. These fishes are renowned for their habit of spitting water
at insects and other arthropods, knocking them down to the water`s surface
where the shooter or another member of the school can then feed upon them
(Timmermans, 2000, 2001; Timmermans and Vossen, 2000; Rossel et al.,
2002; Schuster et al., 2004; Schuster et al., 2006; Temple,
There have been few reports on the biology and ecology of this fishes
(Smith, 1936; Luling, 1963; Allen, 1978; Temple, 2007; Simon and Mazlan,
2008a, b). Studies on the age and growth of fish are important for solving
common problems in fishery management (Polat et al., 2001). Knowledge
of age structure of fish populations allows estimation of growth, mortality
and recruitment and thus contributes to calculations of production rates
of populations (Hilborn and Walters, 1992; Chung and Woo, 1999).
However, to the best of our knowledge there have been no studies concerning
the age characteristics and method of age determination of archer fishes.
Therefore, our main aim was to determine age of these two fascinating
archer fishes (Toxotes jaculatrix, Pallas, 1767 and Toxotes
chatareus, Hamilton, 1822) inhabiting Malaysian estuaries. These data
might help to facilitate further understanding about the biology of this
intriguing fish species.
MATERIALS AND METHODS
Field sampling and laboratory preparation: Samplings of the fishes
were carried out every two months in the estuaries of south Johore (Latitude
01°24`53N, Longitude 104°09`44E) Peninsular Malaysia. A total
of 85 archer fishes comprising Toxotes chatareus and Toxotes
jaculatrix were collected during the period from September 2006 to
June 2007. Out of these specimens, a total of 21 T. chatareus
and 33 T. jaculatrix individual scales were examined and
yielded interpretable age estimates. The rest of the scales were rejected
because they were either broken or unreadable. The sex of the fish was
determined through dissection and direct observation of gonads of the
Samples were collected using 3 layered trammel net, cast and scoop nets,
traps as well as long lines. These gears were set up at random in appropriate
places along the study areas. The mesh sizes of the trammel and cast nets
were 4.2, 6.5, 7.5 and 2 cm, respectively and of the scoop nets 1.5 cm.
The length of the trammel net was 2000, 250 cm for cast net and 40 cm
diameter for scoop net. Specimen identification was carried out in the
field according to the description given by Allen (2004).
Standard length (SL) of the fishes was measured to the nearest centimeter.
Body weight was determined to the nearest 0.01 g accuracy using an electronic
balance. For each specimen about 10 scales were sampled from the central
portion of the body below the lateral line according to Chung and Woo
(1999) and Paul (1967). The scales were treated in 0.5% ammonia solution
for at least 2 days, rinsed thrice with distilled water, dried and mounted
between two microscope slides (Chung and Woo, 1999). The mounted scales
were labeled, observed and photographed under a HITACHI Table Top Scanning
Microscope TM-1000. The scales were weighted to the nearest 0.0001 g precision
using an analytical balance A and D, Model-GR-200.
The daily increment or rings of the scale were repeatedly counted using
the AdobeTM graphic software with slight modification of Mazlan
and Rohaya (2008). Age of the fishes was estimated based on back-calculation
of the number of daily rings (age in days) as well as the annulus (age
in years) on the scale, as shown in Fig. 1a, b (Campana
and Neilson, 1982; Werder and Soares, 1985). Determination of a and b
values were performed by a non-linear equation and the values were obtained
using Chi-square iterative goodness of fit methods with Levenberg-Marquardt
and Simplex algorithms readily developed in MicroCalc. OriginTM
Version 6.0 computer programme (Simon and Mazlan, 2008a). Mean while analysis
of correlation (Pearson`s correlation, r) between scale and fish standard
length was performed using a normal linear regression analysis readily
developed in similar computer programme.
RESULTS AND DISCUSSION
Scales of archer fishes are ctenoid, with 3-9 radii extending from the
focus to the anterior margin. While the inner surface of the scale is
smooth, the anterior and lateral fields of the outer surface are deposited
with regular concentric circuli comprising individual platelets and in
the posterior field circuli are replaced by rows of ctenii (Fig.
1a). Scales of two species showed clear growth zones (Fig.
1a) with each zone consisting of wide translucent band and narrow
The rate of somatic growth is indicated or corresponded by the interspaces
between circuli. Rapid growth is characterized by circuli which are relatively
apart and slow growth is characterized by closely packed circuli. An annulus
is identified as the region with most densely packed circuli preceded
and followed by regions of smooth transitions to regions with wide interspaces
between circuli (Fig. 1a).
Scale from an age 2+ individual archer fish (a) external
morphology with annulus (I = 1st annulus, II = 2nd annulus) (b)
electron micrograph showing daily increment/growth rings
The length and weight of scales were highly correlated (r2
= 0.925) (Fig. 2) and exponent b = 2.917 indicated that
scale length augmented as scale weight increased. There was a linear correlation
between scale length and SL (r = 0.8166) (Fig. 3).
A total of three age classes were identified from the 54 specimen examined.
The results demonstrated for T. jaculatrix in the size
of range 7.8-12.7 cm SL (n = 33, 9 female and 24 male) that estimated
ages were from 260-733 days or less than 1 years to above 2 years, while
for T. chatareus ranging from 6.9-12.4 cm SL (n = 21, 5
female and 16 male) the estimated ages were from 265-413 days or less
than 1 years to 1-2 years respectively (Fig. 4). In
the present study we observed that <1 years samples were dominated
in number than 1-2 years and >2 years samples (Fig. 4).
||Relationship of scale length and weight of archer fishes
Relationship between scale length and SL of archer
fishes (Number of sample, n = 54)
||Age of archer fishes (<1 = < 365 days, 1-2 = 365-730
days, >2 = >730 days)
Ageing of fishes from tropical waters has been reported through annual
increments in calcified structures such as scales (Werder and Soares,
1985; Mayekiso and Hecht, 1988; Chung and Woo, 1999), dorsal and pectoral
spines (Pantulu, 1961; Ezenwa and Ikusemiju, 1981), vertebral centra (Brown
and Gruber, 1988) and otoliths (Fowler and Doherty, 1992). Nevertheless
scales are the easiest to collect and process. Using scales as structures
for ageing also avoids sacrificing the precious rare specimens like in
ageing methods employing otoliths. In this study the reliability of scale
readings was increased by sampling scales only from a fixed position,
at the ventral side where the scales have large uniform size, better symmetry
and high legibility. In other similar study elsewhere, the use of scales
for aging of Oncorhynchus clarki, Pomacantus imperator and
Parapersis colias resulted a significant accuracy with some ambiguity
depending on the fish species (Kruse et al., 1997; Chung and Woo,
1999; Carbines, 2004).
Present results also in fully agreement with Chung and Woo (1999) as
extremely senescent specimens were unavailable in this research; annuli
readings have been relatively legible and reliable. Information on the
growth of archer fishes in the Asiatic regions is still lacking, because
the species is relatively scarce and specimen collection is cumbersome
within a complex rooting system of mangrove forest complimented with their
sharp eye vision and fast swimming speed.
In conclusion, the present study found that most of the archer fish population
in the study areas comprises juvenile age group (<1 year) in comparison
to sub-adult and adult age group (1-2 years). Present results also found
that, the use of scales in age determination for archer fishes is more
efficient likewise those reported for Pomacantus imperato in tropical
waters. Furthermore the population of archer fish species in Malaysian
estuaries is dwindling over time due to fishing pressure and habitat destruction.
Therefore, the use of scales in age determination method in the present
study provides a significant finding without scarifying this rare fascinating
The authors gratefully acknowledge suggestions and criticisms of three
anonymous reviewers that greatly improved the manuscript. This study was
funded by the Malaysia government through UKM-Science Fund grant # 04-01-02-SF0124.
The authors would like to express their thanks to all dedicated laboratory
technicians especially Mr. Azarindra and Mr. Husdy for their help in collecting
fish used in this study. The technical assistance swiftly provided by
Dr. Azman throughout capturing photographs of scales is deeply acknowledged.
This study represents part of first author`s Ph.D work.
Allen, G.R., 1978. A review of the archer fishes (family Toxotidae). Rec. West. Aust. Mus., 6: 355-378.
Allen, G.R., 2004. Toxotes kimberleyensis, a new species of archerfish (Pisces: Toxotidae) from fresh waters of Western Australia. Records Aust. Mus., 56: 225-230.
Direct Link |
Brown, C.A. and S.H. Gruber, 1988. Age assessment of the lemon shark, Negaprion brevirostris, using tetracycline validated vertebral centra. Copeia, 3: 747-753.
Campana, S.E. and J.D. Neilson, 1982. Daily growth increments in otoliths of starry flounder (Platichthys stellatus) and the influence of some environmental variables in their production. Can. J. Fish. Aquat. Sci., 39: 937-942.
Carbines, G., 2004. Age determination, validation and growth of blue cod Parapercis colias, in Foveaux Strait, New Zealand. N. Z. J. Mar. Freshw. Res., 38: 201-214.
Chung, K.C. and N.Y.S. Woo, 1999. Age and growth by scale analysis of Pomacanthus imperator (Teleostei: Pomacanthidae) from Dongsha Islands, southern China. Environ. Boil. Fish., 55: 399-412.
Ezenwa, B.I.O. and K. Ikusemiju, 1981. Age and growth determinations in the catfish, Chrysichthys nigrodigitatus (Lacepede) by use of the dorsal spine. J. Fish. Biol., 19: 345-351.
CrossRef | Direct Link |
Fowler, A.J. and P.J. Doherty, 1992. Validation of annual growth increments in the otoliths of two species of damselfish from the Southern Great Barrier Reef. Aust. J. Mar. Fresh. Res., 43: 1057-1068.
Hilborn, R. and C.J. Walters, 1992. Quantitative Fisheries Stock Assessment: Choice, Dynamics and Uncertainty. 1st Edn., Chapman and Hall, International Thomson Publishing, New York.
Kruse, C.G., W.A. Hubert and F.J. Rahel, 1997. Using otoliths and scales to describe age and growth of yellowstone cutthroat trout in a high-elevation stream system, Wyoming. Northw. Sci., 71: 30-38.
Luling, K.H., 1955. Schutzenfische (Toxotidae). Die. Aquarien. Terrarien. Z., 8: 179-184.
Luling, K.H., 1963. The archer fish. Scientific Am., 209: 100-109.
Mayekiso, M. and T. Hecht, 1988. Age and growth of Sandelia bainsii Castelnau (Pisces: Anabantidae) in the Tyume River, Eastern Cape (South Africa). S. Afr. J. Zool., 23: 295-300.
Mazlan, A.G. and M. Rohaya, 2008. Size, growth and reproductive biology of the giant mudskipper, Periophthalmodon schlosseri (Pallas, 1770), in Malaysian waters. J. Applied Ichthyol., 24: 290-296.
CrossRef | Direct Link |
Pantulu, V.R., 1961. On the use of pectoral spines for the determination of age and growth of Mystus gulio (H). Proc. Natl. Inst. Sci. India, 27B: 1-30.
Paul, L.J., 1967. Early scale growth characteristics of the New Zealand Snapper, Chrysophrys aurats (Forster), with reference to selection of a scale-sampling site. N. Z. J. Mar. Freshwat. Res., 2: 273-292.
Polat, N., D. Bostanci and S. Yilmaz, 2001. Comparable age determination in different bony structure of Pleuronectes flesus luscus Pallas, 1811. Inhabiting the Black Sea. Turk. J. Zool., 25: 441-446.
Direct Link |
Rossel, S., J. Corlija and S. Schuster, 2002. Predicting three-dimensional target motion: How archer fish determine where to catch their dislodged prey. J. Exp. Biol., 205: 3321-3326.
Direct Link |
Schuster, S., S. Rossel, A. Schmidtmann, I. Jager and J. Poralla, 2004. Archer fish learn to compensate for complex optical distortions to determine the absolute size of their aerial prey. Curr. Biol., 14: 1565-1568.
Schuster, S., S. Wohl, M. Griebsch and I. Klostermeier, 2006. Animal cognition: How archer fish learn to down rapidly moving targets. Curr. Biol., 16: 378-383.
Simon, K.D. and A.G. Mazlan, 2008. Length-weight and length-length relationship of archer and puffer fish species. Open Fish Sci. J., 1: 19-22.
Simon, K.D. and A.G. Mazlan, 2008. Trophodynamic analysis of archer fishes (Toxotes chatareus and Toxotes jaculatrix). Proceedings of the IOC/WESTPAC 7th International Scientific Symposium, May 21-25, 2008, The Magellan Sutera, Sutera Harbour Resort, Kota Kinabalu, Sabah, Malaysia, pp: 1-18.
Smith, H.M., 1936. The archer fish. Nat. Hist., 38: 2-11.
Smith, H.M., 1945. The fresh-water fishes of Siam, or Thailand. Bull. US. Nat. Mus., 188: 1-622.
Temple, S.E., 2007. Effect of salinity on the refractive index of water: Consideration for archer fish aerial vision. J. Fish. Biol., 70: 1626-1629.
CrossRef | Direct Link |
Timmermans, P.J.A. and J.H.M. Vossen, 2000. Prey catching in the archer fish: Does the fish use a learned correction for refraction?. Behav. Process., 52: 21-34.
Timmermans, P.J.A., 2000. Prey catching in the archer fish: Marksmanship and endurance of squirting at an aerial target. Neth. J. Zool., 50: 411-423.
Direct Link |
Timmermans, P.J.A., 2001. Prey catching in the archer fish: Angles and probability of hitting an aerial target. Behav. Process., 55: 93-105.
CrossRef | Direct Link |
Werder, U. and G.M. Soares, 1985. Age determination by sclerite numbers and scale variations in six species from the central Amazon (Osteichthyes, Characoidei). Anim. Res. Dev., 21: 23-46.