Description of the morphological deformities in fish in general and skeletal abnormalities in particular have very good attendance in the literatures (Tutman et al., 2000; Jawad and Hosie, 2007; Jawad and Öktoner, 2007;Jawad et al. 2007; Jawad et al., 2010; Al-Mamry et al., 2010). Because of their high incidence .in polluted areas, they are used as indicators of the environmental pollution (Bengtsson, 1979). In aquaculture and in the wild, cases of deformity involve absence of the tail, or partial tail (single-lobed), double or triple tail or lobes, compression (Honma, 1990; Dunham et al., 1991; Lemly, 1993; Honma, 1994; Divananch et al., 1996; Jawad et al., 2010). The only caudal deformity case reported from the Omani waters is that of the mullet species, Moolgarda pedaraki (Jawad and Al-Mamry, 2012). Pampus argenteus (Family: Stromateidae) is a benthopelagic, marine and oceanodromuous species that lives in the Omani waters of the Arabian Gulf in particular and in the Indo-West Pacific from the Arabian Gulf to Indonesia, north to Hokkaido and Japan (Froese and Pauly, 2010). In these areas, it has high local economic importance, mostly living and reproducing in the sea during its whole life cycle (Cruz et al., 2000). It is exposed to many physical and chemical variations, from temperature to pollution, in these most threatened ecosystems (Araghi, 2010). This study describes a case of tail deformity in one specimen of the teleost fish P. argenteus and shows how it possible for the environmental pollution to have such an effect on fishes which in turn it draws the attention of the society to care for the health of their environment.
 

Ten specimens of Pampus argenteus showing variable cases of deformity of the caudal fin (TL 250-258mm, SL 168-170 mm, 320g) were caught by cast net from the Omani waters of the Arabian Gulf at Khasab City, South west of the Arabian (Figure 1).Ten normal specimens varying in size between 183-260 mm, TL, 173-180mm SL were obtained from the same locality for comparison. There were a total of 250 fish specimens in the catch and the deformed specimens represent 4% of the total catch. The specimens were measured using digital calliper to the nearest mm and weight using electronic balance to the nearest gram. One of the deformed specimens that shown to bear all types of abnormalities present in the other deformed specimens and considered the most deformed specimen among the rest of the abnormal specimens is radiographed with ordinary X-rays to interpret the skeletal anomaly and to check for other anomalies. The specimens were deposited in the fish collection of the Marine Science and Fisheries Centre, Ministry of Fisheries Wealth, Muscat, Sultanate of Oman, catalogue number OMMSTC 1095. Water sample was taken to measure the ecological variables such as water temperature, salinity, dissolved oxygen and pH using the instrument ‘Hydrolab’ (Model SVR 2-SV) which can measure the hydrographic parameters within the ranges of the following: temperature -5 to +45 C; DO 0 to 20 mg/l; salinity 0 – 50 ppt; pH 0 to 14 and depth 0 to 200 m. For measuring the heavy metals in the water where the deformed fish specimens obtained, the method of Alyahya et al. (2011) was used. In this method, the water sample was filtered through a 0.45-μm membrane filter before being acidified with concentrated nitric acid. The dissolved trace metals were concentrated by using chelex-100 resin following the procedure of Riely and Taylor (1968). Then the water sample was analyzed, in triplicate, using an atomic absorption spectrophotometer (Model SP 9) for analysis of As, Cd, Hg, Pb, and Zn. Deionised water was used throughout the analysis. Values for hydrographic parameters are shown in Table 1 and values of heavy metals are shown in Table 2.

 

Caudal fin deformity was visible on the fish bodies immediately after capture when compared with the normal specimen (Figures 2 a, b). The external examination of the deformed caudal fin showed that this fin has lost its both dorsal and ventral lobes. In addition, the caudal fin rays appeared to be short, wavy and stuck together. In comparison with the x-ray of the normal specimen (Figures 3 a, b), the abnormal specimen showed some severe anomalies, these are: missing the whole caudal skeleton which includes the following bones, the hypural bones, urostyle, epurals and parhypural; missing two caudal vertebrae; deformed centrum of the vertebra number 35, the last vertebra in the vertebral column of this specimen, and losing its both the neural and haemal spines; neural spine of the vertebrae 33 and 34 are not straight and not curved backward as in the normal specimen; haemal spine of vertebrae 32, 33 and 34 are straight and short with haemal spine of vertebra 32 is the shortest; and vertebra 33 has two haemal spines. Other minor anomalies were also detected these are: strongly undulated caudal fin rays; wavy posterior 14 pterygiophores (counting from the posterior end of the dorsal fin) supporting the dorsal fin; and wavy last five anal fin rays and their supporting pterygiophores.

 

Figure 2 A: Normal fish specimen of Pampus argenteus (TL 183 mm, SL 173 mm). B: Abnormal fish specimen (TL 250 mm, SL 168 mm)

 

Figure 3 Radiograph of A. normal specimen of Pampus argenteus (TL 183 mm, SL 173 mm). B. abnormal specimen (TL 250 mm, SL 168). Caudal fin of abnormal specimen

 

The disturbances in the environment where the fish lives can be traced and monitoured through the appearance of spinal deformities which can be a sign of the existence of such disturbances in the ecosystem.Therefore, it is important to makr people are aware of how healthy is the environment that they living in. In fishes, in general, the caudal fin has an important role in maneuvering and steering functions; therefore it must be constructed so as to cope with hydrodynamic stresses with the least possible expenditure of energy (Boglione et al., 1993). Any anomaly in the caudal fin will impair the flexibility of the tail, so hindering the performance of the fish (including the capacity to get food and to avoid predators). As far as the author is aware, no similar case of anomalies is reported on any other fish species.
 

There are several potential environmental factors that cause the caudal fin deformities, these are: heavy metals such as As, Cd, Hg, Pb, and Zn (Sloof, 1982); and the effect of exposure to light and heat during reproduction (Koo & Johnston, 1978). The data for temperature of sea water shown to be higher than those reported by Thangaraja et al. (2011) for the same area and the results of the heavy metals analysis has shown that the levels of of As, Cd, Cr, Pb, and Zn exceeded the standard values in sea water. Such factors are also reported by others to be present in the Omani waters of the Arabian Gulf where biota in the Omani waters has shown to be exposed to different environmental factors and vulnerable to different levels of heavy metals (Reid et al., 2004; De Mora et al., 2004, 2005; Tolosa et al., 2005; Araghi, 2010). Those environmental and pollution factors could well affect the specimen of P. argenteus as they are shown to be the cause behind skeletal anomalies in the other fish species collected from the Arabian Gulf area (Laith Jawad, unpublished data).
 

In the present report, the percentage of the deformed fish is moderate (4%), but on the other hand is alarming. If such percentage showed gradual increase in the future, then it could influence the fishery especially P. argenteus is considered high commercially important species (Tutman et al., 2000).
 

I would also like to thank the Ministry of Fisheries Wealth, Marine Science and Fisheries Centre, Ministry of Fisheries Wealth and the directorate of Agriculture and Fisheries Developmental Fund for giving us the opportunity to work on the fish samples within the qualitative and quantitative distribution of marine organisms in Sultanate of Oman and to provide the appropriate financial support.