ACTA ICHTHYOLOGICA ET PISCATORIA (2010) 40 (2): 105–108 DOI: 10.3750/AIP2010.40.2.02 THE SLENDER SUNFISH, RANZANIA LAEVIS (ACTINOPTERYGII: TETRAODONTIFORMES: MOLIDAE), IN THE COASTAL WATERS OF THE OMAN SEA Laith JAWAD*, Juma AL-MAMARY, and Lubna AL-KHARUSI Marine Science and Fisheries Centre, Ministry of Fisheries Wealth, Muscat, Sultanate of Oman Jawad L., Al-Mamary J., Al-Kharusi L. 2010. The slender sunfish, Ranzania laevis (Actinopterygii: Tetraodontiformes: Molidae), in the coastal waters of the Oman Sea. Acta Ichthyol. Piscat. 40 (2): 105–108. Abstract. Captures of the slender sunfish, Ranzania laevis, are reported off the coastline of the cities of Sohar and Seeb, Oman Sea, Sultanate of Oman in February and March 2009. Their association with the environmental factors such as warming process is discussed. Keywords: unusual occurrence, Ranzania laevis, slender sunfish, Sultanat of Oman, Oman Sea In February and March 2009, an unusual occurrence of the slender sunfish, Ranzania laevis (Pennant, 1776) (Fig. 1), was recorded along the coasts of the Oman Sea. Two specimens were captured from the coasts of Oman Sea, one from the coast of Sohar city and the other from the coast of Seeb city, by a local fisherman in surface waters (< 10 m) using seine net. The fishes were 495 mm and 507 mm in total length (TL) and 3450 g and 3700 g respectively. Morphometric and meristic details following Jardas and Knežević (1983). The specimens were deposited in the fish collection of the Marine Science and Fisheries Centre, Ministry of Fisheries Wealth, Muscat, Sultanate of Oman, catalogue numbers OMMSFC 0633 and 0666, respectively. Morphometric and meristic details are given in Table 1. Ranzania laevis, the monotypic type species of Ranzania, is epipelagic and cosmopolitan. Its distribution includes Florida (USA), Martinique, Venezuela, and Brazil in the Western Atlantic (Dennis et al. 2004); from Scandinavia to Sierra Leone in the Eastern Atlantic (Tortonese 1986, 1990), the Mediterranean Sea (Specchi and Bussani 1973, Parenzan 1978; central California, USA to Chile in the Eastern Pacific where it is rare north of Mexico (Eschmeyer et al. 1983), in the western central Pacific (Masuda et al. 1984, Shao unpublished**) and in the eastern Indian Ocean (Fujita and Hattori 1976, Hutchins 2003). Previous studies on the ichthyofauna of the Red Sea, the Arabian Sea, Oman Sea, and the Persian Gulf have not indicated the presence of R. laevis (see: Botros 1971, Kuronuma and Abe 1972, Chakraborty 1984, Al-Baharna 1986, Randall 1986, 1995, Hussain et al. 1988, El-Etreby 1993, Al-Sakaff and Esseen 1999). Although several captures have been reported from * temperate waters (Parin 1968), the capture reported herein is the first for the Oman Sea and the northernmost record of slender sunfish adult for the Indian Ocean. Frasser-Brunner (1951) recognized two subspecies of the slender sunfish, R. laevis laevis in the Atlantic Ocean, and R. laevis makua in the North Pacific. The two subspecies differ in a number of characters such as the position of the axil of pectoral fin in relation to the level of centre of eye and height of anal fin relative to the head length. The external morphology of the specimens at hand agrees with the description provided by Frasser-Brunner (1951) and matches the characteristics of the subspecies R. laevis laevis in having axil of pectoral fin well below level of centre of eye and height of anal fin less than 3/5 length of head. The latter character fits one of the specimens, but not the other. Mixture of subspecific characters Fig. 1. Ranzania laevis, 495 cm TL, Sohar, Sultanate of Oman, Gulf of Oman, OMMSFC 0633 (photo: Laith A. Jawad) Correspondence: Laith A. Jawad, Marine Science and Fisheries Centre, Ministry of Fisheries Wealth, P.O. Box 427, Postal Code 100, Muscat, Sultanate of Oman, phone: +968 9961 0015, fax: +968 2474 0159, e-mail: laith_jawad@hotmail.com ** Shao K.-T. 1997. A checklist of fishes recorded in Taiwan and their distribution around Taiwan. Unpublished database. 106 Jawad et al. Table 1 Morphometric and meristic characters of Ranzania laevis collected from the Gulf of Oman compared with the specimens obtained from the literature (NA = not available) Character (mm) and ratios (%) Morphometrics Total length (TL) Standard length % TL Head length (HL) % TL Prepectoral fin length % TL Predorsal fin length % TL Preanus length % TL Preanal fin length % TL Greatest body depth % TL Body depth at pectoral fin origin % TL Pectoral fin length (PFL) % TL Dorsal fin length (DFL) % TL Clavus length % TL Anal fin length (AFL) % TL Preorbital length % HL Eye diameter % HL Mouth diameter % HL Interorbital distance % HL Dorsal fin base % DFL Pectoral fin base % PFL Anal fin base % AFL Meristics Number of dorsal fin rays Number of pectoral fin rays Number of anal fin rays Number of clavus fin rays Present study specimens OMMSFC 0633 OMMSFC 0666 495 470 94.9 168 99.7 85 17.2 443 89.5 370 99.3 379 99.2 250 50.5 235 47.5 102 20.6 127 25.7 182 36.8 110 22.2 67 39.9 28 17 25 15.2 50 25.8 57 1.2 26 25.5 62 56.4 17 14 18 19 in slender sunfish is not unusual event and was reported for a specimen collected from Mauritius (deposited in Natural History Museum, London) reported by FraserBrunner (1951), and it is also observed in the two slender sunfish specimens collected recently from marine waters of Iraq, northwestern Persian Gulf (Jawad et al., unpublished data). As far as the authors are aware, few studies have given morphological measurements and meristic data for the 507 470 92.7 186 36.7 190 31.8 450 88.8 356 70.2 418 82.9 230 45.4 218 43.0 106 20.9 129 25.6 170 33.7 130 25.8 70 37.6 30 1.61 15 8.1 59 31.9 52 40.3 24 22.6 48 34.6 15 12 17 18 Phillipps (1941) Jardas and Knežević (1983) 374 NA NA 142 37.9 NA NA NA NA NA NA NA NA 152 40.6 NA NA 66 17.6 NA NA 104 27.8 84 22.5 NA NA NA NA NA NA NA NA 89 NA NA NA NA NA 420–560 490–528 92.5–94.3 152–193 34.3–36.8 200–220 37.7–39.3 385–496 88.4–91.7 325–400 76.9–77.4 NA NA 168–280 38.6–50 NA NA 103–110 194–196 130–160 24.5–28.6 NA NA 137 25.8 55–73 35–38.5 255–350 13.4–18.1 NA NA NA NA 45–70 34.6–43.8 27–30 26.2–27.3 45 32.8 15 14 18 19 17–18 13–14 18–20 17–19 recorded sunfish specimens collected from the seas around the world (Phillipps 1926, Jardas and Knežević 1983). These data are here compared with data obtained in the present study (Table 1). The maximum size reached by this species is 1000 mm in total length (TL) (Claro 1994). The size of our specimens fall near the upper maximum size limit given for a series of R. laevis specimens collected from various localities around the world (Phillipps 1926, Jardas and Knežević 1983, Castro and Ranzania laevis in coastal waters of the Oman Sea Ramos 2002). The other body proportions agree well with those given by other authors (Table 1). Although it could be several explanations for the presence of this fish in the coastal waters of Oman Sea (e.g., ballast water of ships playing between Europe and the Persian Gulf). Strictly marine and cosmopolitan, R. laevis is a taxon with different ecological preferences, one of which for example, has a larval pelagic existence in coastal waters (Robison 1975, Wan and Zhang 2005). It could be related with changes in environmental factors such an increase of sea surface temperature. Warmer water masses might cause the slender sunfish to proceed further north of its native distribution. A sudden southern warming process of the sea surface in the Oman Sea area was evident during the period January–February 2009 where warm water masses were recorded entering through the Straight of Hurmoz (Al-Yamani, personal communication). The relation between a sudden rise in sea surface water temperature and the presence of R. laevis was also observed by Castro and Ramos (2002), who related the presence of R. laevis off Gran Canaria (Canary Islands) to the sudden west-east warming process of the sea surface in the central Atlantic. Since only two specimens were collected and since no further individuals were obtained, it is premature at this stage to consider this species among the fish fauna of Oman. It should only be considered as such, if a breeding population of this species is maintained in the area. 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