Wadi Fish of the UAE [2]

Introduced Species

Two introduced varieties of freshwater fish are known to occur in the UAE. One, the tilapia, has been actively introduced and is now relatively widespread and well established in suitable habitats. It is thought to be represented by at least two or three species and their hybrids. The other, the molly, is so far known from only a single agricultural site.

Tilapia (Oreochromis spp.): The tilapiines are a sub-group of the very large and diversified family of fishes, the Cichlidae, most of which are native to tropical and subtropical Africa. The name tilapia is used to refer to several related genera including the genus Tilapia. A few tilapia species are bred commercially in large numbers as a food fish. In Arabia, tilapia have been introduced in modern times to many freshwater bodies of all kinds (including water tanks and irrigation channels) for purposes of algae, weed and mosquito control. Some are now bred locally for these purposes.

Tilapia are typically much larger than other local wadi fish, reaching in excess of 15 cm. The most common variety is a pale beige colour. Smaller and/or immature individuals are usually marked with a line of several diffuse dark blotches (or sometimes vertical bars) along the side of the body. Larger individuals show vertically striped and variably tinted dorsal and tail fins and the dark blotches on the body are reduced or absent. A few populations are a dull blue-green colour overall. A variety bred in Abu Dhabi in large numbers is black with red margins on the pectoral and tail fins. This variety has not been seen in the mountains, with the exception of the Wadi Shi reservoir near Khor Fakkan, but it can be found elsewhere in irrigation ditches and pond environments in certain agricultural areas. Tilapia colour patterns may vary with the emotional state of the fish, and in breeding colour local tilapia males of all varieties exhibit vivid blue-white lips.

Apart from colour, all of the tilapia found in the UAE are very similar in appearance. Seen from above, the large dark eyes are prominent. The body is widest at the head and tapers forward to a broad, blunt mouth. Seen from the side, the body is relatively deep in comparison with other local fish. The tail is unforked and the dorsal fin is greatly elongated. Sexual dimorphism is generally limited to features that are not always easy to observe under field conditions, e.g., males typically have longer pelvic and dorsal fins. The different colour varieties seen in the UAE can sometimes be found together. Black and pale individuals were observed in mutual courtship behaviour in a pond near Ruwayyah in Dubai, along with occasional intermediate, mottled forms. It is not known to the author whether the observed varieties represent different species or whether the less conspicuous pale form represents a colour reversion.

Identification of the tilapia species present in the UAE is uncertain and problematic. At least four species are reported to have been introduced elsewhere in Arabia: Tilapia zillii [6], Oreochromis aureus (the blue tilapia), O. mossambicus (the Mozambique tilapia), and O. niloticus (the Nile tilapia) [11]. Large scale commercial culture of tilapia is limited almost exclusively to the latter three Oreochromis species, with the Nile tilapia being by far the most common. Unfortunately, breeding stocks are not always pure, and tilapia species hybridise readily. As a result, it is often difficult to be certain what species may be present in a given population. Even experts do not rely confidently on appearance, but resort nowadays to biochemical methods [12]. At least two and possibly all three of the commercial Oreochromis species, as well as hybrids, may be present in the UAE. The black variety resembles the typical O. mossambicus, the most common pale variety is a reasonable candidate for O. niloticus, and the blue-green variety may correspond to O. aureus. These identifications remain to be confirmed, however.

Behavioural characteristics support the general taxonomy suggested above, and can also facilitate field identification of tilapia. At breeding time local tilapia males each excavate a shallow bowl in a sandy bottom area, which they then patrol as their territory and defend against other males. This appears to be true of all colour varieties seen in the UAE. In suitable areas, many territories may be established adjacent to each other, separated by less than a bowl’s width, each patrolled by its resident male. This behaviour is typical of Oreochromis species, all of which are polygamous female mouthbrooding species in which the eggs are fertilised and hatched in the female’s mouth, without further involvement by the male [13].

Tilapia are omnivores with a strong herbivorous tendency. The common varieties are notoriously voracious, hardy and prolific species native to African rivers that vary seasonally, predisposing the fish to be able to tolerate considerable fluctuations in temperature, salinity, water quality and food resources [13]. They can sometimes survive even limited temporary desiccation of their environment by burying themselves in damp mud. As a result, concern has been expressed that the introduction of tilapia will adversely affect the native fish population.

Molly (Poecilia spp., formerly Mollinesia spp.): While not strictly a wadi fish, the molly is mentioned here because it is the only other freshwater fish presently known to ocur in the UAE, and it may yet be found in mountain front areas in association with agriculture and human settlements. Mollies are native to tropical and subtropical America. The black molly, a selectively bred variety, is a popular aquarium fish available worldwide. It is live-bearing, prolific, and easily bred. Mollies were reported more than a decade ago from scattered wells and irrigation works in eastern Saudi Arabia, where they originated from private aquaria [11]. They are also known in similar circumstances from Bahrain [14]. In both places they have been observed to occur in three colour varieties – black (the commercial variety), pale beige (considered to be the original wild colour) and mottled black-and-pale. This represents a reversion of the aquarium stock to the original wild colour due to indiscriminate breeding [11].

In the UAE, mollies were recognised only in early 1998 [14] and exhibited the same three colour patterns as mentioned above. They were seen in irrigation ditches at Ruwayyah, an agricultural area about 30 km inland from Dubai, and may also be present in other large agricultural areas in the Dubai hinterland. Surface water in these areas is maintained by pumping ground water, and the molly population is in this sense artificially sustained.

Geographical Distribution of Species

Figure 1 shows the distribution of freshwater fish species in the wadis of the UAE and neighbouring Oman, where they have been observed by the author. Wadi Jizzi in Oman is shown for orientation but was not investigated. Most fieldwork was conducted during the period May 1996 to July 1998. The resulting compilation gives a reasonably comprehensive account of the existing distribution, although not all wadis are included nor were they all surveyed with wadi fish exclusively in mind. In the wadis shown, the fish fauna was observed conscientiously and the failure to observe a species is believed to indicate its absence. In a few instances local residents were consulted, and their information always confirmed the author’s observations, even where this was not what was anticipated.

At least a few generalisations can be made from the distributions shown:

(1) Garra barreimiae is the most common and widespread species, and is often the only species present. With few exceptions it is present at every location where any wadi fish at all are present. In addition, where G. barreimiae is present along with other freshwater fish, its distribution normally continues further upstream than that of the other species. Nevertheless, G. barreimiae is absent anomalously in several significant freshwater locations, including Wadi Safad and Wadi Hiluw on the East Coast of the UAE and Wadi Baraq on the west flank of the mountains. A. dispar, by contrast, is present and abundant in those three wadis. These sites bear further investigation.

(2) Cyprinion microphthalmum is not found north of Wadi Hatta and the mountain corridor from Hatta to the Madam plain. Moreover, it has been found only in larger wadis and tributaries which support relatively large freshwater pools year round.

(3) Aphanius dispar is not found on the west flank of the mountains except in the area from Wadi Hatta northwards. This corresponds to the area of wadis whose route to the sea, although intermittent, can still be discerned in the modern landscape.

(4) Within the area studied, A. dispar and C. microphthalmum are found together only in the Wadi Hatta and Wadi Fayd watersheds. This appears to reflect the northern limit of the range of C. microphthalmum rather than a relationship of mutual incompatibility. Both species are present in significant numbers in Wadi Hatta and Wadi Fayd, and they are understood to co-exist in the many large wadis to the south along the Batinah coast of Oman [6,7].

(5) No freshwater fish are present in the Ru’us Al-Jibal, i.e., the high peaks of the Musandam Peninsula, north and west of Dibba. This area differs both geologically and hydrologically from the mountains to the south. There are no permanent streams and very few permanent pools. Those pools which do exist have been the subject of field attention, and other investigators confirm the absence of fish [1]. On the southern edge of the Ru’us Al-Jibal, A. dispar is present in Wadi Khabb and its tributaries in a few wells and small streams fed by runoff from groundwater pumped for agricultural use, but local residents confirm that these fish have been introduced. Freshwater fish may yet be introduced into modern cisterns or water tanks in other settlements within the Ru’us Al-Jibal, but this is not known to have occurred to date.

Additional possibilities

No native freshwater fish species other than those listed above have been reported in the literature from the UAE or northern Oman. Several different species of Garra, Cyprinion and Barbus (another genus in the carp family), have been identified from the mountains of Yemen and western Saudi Arabia, where the somewhat less arid conditions may support a more diverse freshwater fish fauna than in the UAE. All authors are in agreement that there is no evidence for the exchange of freshwater species between the mountain regions of east and west Arabia [6,7,15]. Primary freshwater fish are not known from other areas of the Arabian Peninsula.

In the course of the present study, a previously unrecognised and apparently native fish was observed in nearby northern Oman, and might potentially be found in the UAE. This is described below in advance of professional investigation and definitive scientific determination.

‘The Hatta Goby’ (identification pending):

This fish was first observed in October 1997 in a remote section of Wadi Qahfi, a tributary of Wadi Hatta, several kilometres below the well-known Hatta Pools. This area is within the Sultanate of Oman, near the UAE border town of Hatta. Live specimens were collected in April 1998. Using the key contained in Krupp (1983) it was possible to identify the fish with reasonable confidence as a goby (Family Gobiidae). This conclusion was seconded by professionals at the Breeding Centre for Endangered Arabian Wildlife in Sharjah, where the specimens are now held.

The Hatta goby is typically found in deeper pools in the wadi bed (i.e., more than one metre deep) along with both G. barreimiae and C. microphthalmum. It is readily distinguishable by its size, colouration and behaviour. In most cases the gobies are the largest fish present, being approximately twice the length of the largest G. barreimiae and as much as one half longer than the largest C. microphthalmum. Maximum length is more than 15 cm. The body is flat-bottomed and elongated, tapering uniformly from the back of the skull to the base of the tail. In colour it is a mottled grey-brown with several brighter, broad, yellow-buff transverse bands across its back. Viewed closely, these are not solid colour bands but are made up of an overall camouflage pattern of yellow and brown.

The tail fin is small, faintly striped and blunt-ended. The pelvic fins are distinctive, being pale, rather round and oriented horizontally, resembling two decorative fans. Consistent with the distinguishing characteristics of gobies, the Hatta goby has two dorsal fins and its pelvic fins are positioned far forward and are fused to form a sucker or grasping organ, but these features are not easy to see in the field. The head is short and wedge-shaped and the skull tapers upwards like that of G. barreimiae. The eyes are small and narrowly set in a dorsal position. The snout is blunt and the broad mouth has a thick upper lip and is set at the anterior ventral edge of the body.

Gobies, most of which are marine species, are typically solitary and territorial, living in holes or under stones [11]. The Hatta goby seems to follow this pattern. It is relatively sedentary, generally resting on the substrate. If approached by an observer while in shallow water, it will normally withdraw or seek cover. In an area of open sand or gravel, it may take cover by burying itself, which it can do almost instantly.

Krupp (1983) mentioned that “unidentified species of marine fishes entering freshwater were reported from Arabia (Gobiidae, Mugilidae) [i.e., gobies and mullets]”. He gave no further details but included gobies in his identification key. The marine goby Bathygobius fuscus, which is distinct from the Hatta goby, has been reported from a tidal influenced drainage ditch in the Qatif oasis along the Arabian Gulf coast of Saudi Arabia [11]. In contrast, it should be emphasised that the Hatta goby is found in a bona fide mountain wadi environment of bedrock, boulders and medium to coarse gravel, more than 35 km upstream from the sea (25km inland and over 15 km within the mountain front itself) at an elevation of almost 300 metres.

Like wadis throughout the Hajar Mountains, Wadi Qahfi is subject to both torrential flooding and significant desiccation. Flash floods have claimed human lives in this wadi within the past decade, but for much of the year water does not flow continuously at the surface, being limited to intermittent shallow channels and isolated deeper pools. Moreover, the outflow from Wadi Qahfi and other tributaries of Wadi Hatta does not normally reach the sea across the broad Batinah coastal plain, except very briefly after exceptional rains. This is not a frequent phenomenon, nor is it believed to have been so in historical times. Archaeological and geological evidence indicates that the climate of southeastern Arabia turned distinctly more arid beginning approximately 4000 years ago, and it is generally accepted that the present day wadi systems of the Hajar Mountains were developed primarily during wetter periods in earlier times.

Against this background, it is significant that the goby population in Wadi Qahfi, although not large, seems well-established and consists of individuals of varying sizes, suggesting the maturation of multiple generations in situ. Assuming an ultimate marine origin, the question remains to be answered as to when and under what conditions the arrival and adaptation of this population occurred.

Additional introduced species

The presence of additional introduced species at discrete permanent freshwater sites in the UAE must be considered likely. Aquarium fish such as guppies (Poecilia reticulata) and platties (Xiphophorus maculatus), in addition to the mollies mentioned above, have been released to the wild in the Eastern Province of Saudi Arabia [11]. Another possibility is Gambusia affinis, which has been introduced elsewhere to control mosquitoes and in Iran is considered to have displaced Aphanius dispar from much of its former range [15]. All of the foregoing species are members of the live-bearing toothcarp family (Poecilidae) and are prolific in captivity. In addition, it would be somewhat surprising if the many foreign agricultural labourers did not occasionally consider the unofficial introduction of species known to them from their home countries.

Conclusion

The study of freshwater fish in the mountains of the UAE and northern Oman remains in its early stages. Scientific studies have so far emphasised western Arabia. Amateur observation remains important in establishing the ranges and behaviour of the various species. Little is known in detail about the life cycles and survival strategies of the local freshwater fish. All of the fish described here, with the exception of tilapia, are maintained at the Breeding Centre for Endangered Arabian Wildlife in Sharjah, which is attempting to learn more about Garra barreimiae in particular. It is hoped that the present contribution will stimulate additional interest and attention.

References

1. pers. comm., M. Sawaf (Arabian Leopard Trust) 1998.

2. Siebert, D. (1994). Preliminary Report on the Freshwater Fish from the Emirate of Fujairah. In: Whybrow, P.J., ed., Preliminary Studies of the Geology and Biology of the Emirate of Fujairah, Report to the Ruler of the Emirate of Fujairah.

3. pers. comm., M.A.R. Khan (Director, Dubai Zoo) 1993.

4. pers. comm., C. Gross (Breeding Centre for Endangered Arabian Wildlife) 1998.

5. pers. comm., S. Jordan (Breeding Centre for Endangered Arabian Wildlife) 1998.

6. Krupp, F. (1983). Freshwater Fishes of Saudi Arabia and Adjacent Regions of the Arabian Peninsula. Fauna of Saudi Arabia, Vol. 5.

7. Banister, K.E. and Clarke, M.A. (1977). The Freshwater Fishes of the Arabian Peninsula. In: The Oman Flora and Fauna Survey 1975, Journal of Oman Studies Special Report, Ministry of Information and Culture, Sultanate of Oman.

8. Krupp, F. (1988). Freshwater Fishes of the Wadi Batha drainage. In: J. Oman Studies Spec. Rept. No. 3, pp. 401-404.

9. Boer, B., Love, M., and Mitchell, W. (1995). Records of Freshwater Fish from the Hatta Area. Tribulus 5.1:28.

10. “Mangroves: Food Factories of the Gulf”. News release, Shell Markets Middle East, 14 July 1996.

11. Ross, W. (1985). Oasis Fishes of Eastern Saudi Arabia. Fauna of Saudi Arabia, Vol. 7.

12. pers. comm., K. Hyland, 1998.

13. Loiselle, P.V. (1987). A Fishkeeper’s Guide to African Cichlids. Salamander Books, London.

14. Anon. “Tropical Fish at Ruwayyah.” In: The Gazelle, newsletter of the Dubai Natural History Group (Feb. 1998).

15. Alkahem, A.F. and Behnke, R.J. (1983). Freshwater Fishes of Saudi Arabia. Fauna of Saudi Arabia, Vol. 5.

16. Krupp, F., and Schneider, W. (1989). The Fishes of the Jordan River Drainage Basin and Azraq Oasis. Fauna of Saudi Arabia, Vol. 10.

Gary R. Feulner, P.O. Box 9342, Dubai, U.A.E.