Gary R. Feulner
The three freshwater fish species native to the mountains of the UAE, Garra barreimiae, Cyprinion microphthalmum and Aphanius dispar, are described from a field perspective and their distribution is illustrated and discussed. C. microphthalmum is reported from the UAE for the first time. Introduced tilapia, probably Oreochromis spp., are also described and their distribution illustrated. The recent recognition of introduced mollies Poecilia spp. is also noted. Finally, a newly observed fish believed to be a native species of goby Gobiidae found within Oman, adjacent to the UAE border, is described pending determination.
Native Species
The scarcity of fresh surface water in the UAE (as in Arabia generally) limits both the number and variety of freshwater fish that are found. Only three native species of fish are known to occur in the mountain wadis of the UAE. These are Garra barreimiae, Cyprinion microphthalmum and Aphanius dispar (the Arabian killifish). The first two are members of the carp family (Cyprinidae), the third belonging to a large family commonly known as egg-laying toothcarps (Cyprinodontidae). Except for the Arabian killifish these species do not have common names either in English or, apparently, in Arabic [1]. No UAE wadis flow continuously at the surface throughout the year, so all local wadi fish must be able to survive for extended periods in isolated pools. However, little is known in detail about their adaptations and life histories and even basic information on diet, reproduction and longevity is presently lacking [2].
@
Garra barreimiae: This is by far the most common species, and if fish are present in a mountain wadi in the UAE, G. barreimiae is normally among them. First described in 1956 and named after the Buraimi oasis, it is endemic to the UAE and northern Oman. It is the only species seen in many wadis and may be the only local species that is able to survive regular and complete desiccation of its environment.
G. barreimiae is a bottom-feeder feeding by means of a specialised plate within the oral opening (called the “mental disc”) which functions as a sort of suction device. G. barreimiae resembles a catfish as it nuzzles its way across gravel or over rock surfaces. The body is relatively long with a flat underside, blunt snout and a wedge-shaped head that is trapezoidal in cross-section, tapering upwards. Its large, heavy scales give it an armoured, somewhat primitive appearance. The pectoral fins are large ovals and the tail fin is forked symmetrically. The maximum size is estimated to be about 8.0 cm but the normal range is approximately 3.5-6.0 cm.
In colour it is a mottled brown, typically rather dark but varying with the surroundings. One consistent feature that is particularly useful in the field is a thin but distinct, pale transverse line just behind the head, that appears to demarcate the head from the body of the fish. The dark eye has a yellow or orange spectacle. Larger adults (>4.0 cm) characteristically have a red-tinged tail and pectoral fins, a white tip on the dorsal fin and a blue-white marking at the fork of the tail. The population in a given pool may exhibit consistent distinctive variations, e.g. orange head markings.
Larger adults are relatively sedentary and sometimes rest on the bed, whereas juveniles are more active, but all move frenetically when approached in a shallow pool where they are vulnerable to terrestrial predators. Occasionally, when feeding, they may be seen to twist sharply and rub their bodies against rocky surfaces or gravel, briefly flashing their white bellies. The purpose of this motion is unknown, but it may be an attempt to dislodge parasites. Larger individuals often appear to maintain at least temporary territories with a radius of several inches, within which they forage and chase away smaller intruders.
G. barreimiae can travel limited distances out of water. For example, they can easily negotiate damp rock surfaces between small puddles in shallow mountain rivulets. Khan has described a video taken by Mike Shepley in which G. barreimiae are seen to ascend a steep rock face during rain [3]. Gross suggests that it is a behavioural tendency of the fish to explore upstream in this manner. Captive G. barreimiae sometimes exit their tanks at points where water has dripped down the inside glass above the waterline [4].
The author once observed some two dozen or more medium size G. barreimiae attempt to climb a 4-metre waterfall consisting of several steep chutes. They ascended on the wet surface of the splash zone immediately adjacent to the main flow of water, sometimes wriggling, sometimes jetting forward, resting periodically with pectoral fins spread, the mental disc apparently engaged for suction, and the tail twisted and pressed flat against the rock. Most did not ascend more than about a metre but several managed to ascend almost 3 metres, although it was not clear that any fish were ultimately successful, owing to the difficulty of the uppermost chute. The fish were unfortunately not observed climbing until after one of the author’s companions had settled into the pool at the base of the waterfall, and so it is not known whether their behaviour was entirely spontaneous. However, fish continued to embark on the falls intermittently over a period of 15 minutes or more, typically in small groups.
According to Khan, G. barreimiae are thought to lay their tiny eggs in wadi gravel, where they hatch only when conditions are suitable. Some of the eggs may adhere to the feet of birds that come to feed or drink, and so be transported and released in distant pools [3], although not everyone accepts this conventional wisdom. Gross notes that attempts to breed G. barreimiae have been notoriously unsuccessful. Adults are reported to eat the eggs of their own species and Gross suggests that this is to be expected in a nutrient-poor environment like that of most UAE mountain wadis. He speculates that spawning is somehow triggered by rain or thunderstorms, thereby ensuring rapid dispersal of the eggs, which are known to hatch within 24 hours [4]. This hypothesis is apparently strengthened by recent successful breeding at the Breeding Centre for Endangered Arabian Wildlife in Sharjah, UAE [5], although would require a reservoir of freshwater and adult fish to exist year-round in every wadi in which G. barreimiae is found. It remains to be determined whether this criterion is satisfied in all cases.
The genus Garra is known from East Africa to South Asia [6]. A small number of species and subspecies are endemic to the mountains of southwestern Arabia [6]. The closest relative of G. barreimiae is thought to be Garra persica, a species widespread in southern Iran [6]. Early work distinguished two subspecies of G. barreimiae in the UAE and Oman,G. b. barreimiae and G. b. shawkahensis, as well as a second species of Garra from the south of the Jebel Akhdar, G. longipinnis [6,7]. However, the total number of G. barreimiae specimens was small, and these were collected from only five sites including Muscat, Buraimi and Wadi Shawkah. It remains to be seen whether work based on more extensive sampling and a better understanding of the widespread but disjunctive distribution of G. barreimiae within the Hajar Mountains will validate these early distinctions. Krupp has since described an additional subspecies, G. b. gallagheri, that inhabits the relatively distant and discrete Wadi Batha watershed in Oman, east of the Wahiba Sands [8]. The criteria by which experts generally distinguish subspecies of freshwater fish are arcane and often statistical, and are not well suited to field application by non-specialists. The author has not attempted to distinguish possible subspecies in the course of the present study.
G. barreimiae is caught and eaten by some mountain residents. Although this is presumably now relatively rare, the author has observed local fishermen harvesting this species from a stream, using a stone dam to channel the fish onto a portable sieve-like platform that can be made from palm ribs, wire mesh or nylon netting. The remains of such operations can be seen on occasion. This method can be very effective, eliminating virtually every fish in the affected area [4]. The author’s own observations of recently fished streams, where only the smallest juvenile fish could be found, supports this claim. Discussion with local fishermen and examination of their catch indicates that only G. barreimiae is taken, even when other species are present in significant numbers.
@
Cyprinion microphthalmum mascatensis: Cyprinion is an Asian genus of the carp family. C. microphthalmum has long been known from Pakistan, Afghanistan, Iran and the Muscat area [6], but was only confirmed from areas near the borders of the UAE in 1995 [9] and from just inside the UAE itself (at Hatta and Hadf) by the author in 1998. Congeners are known from within its Asian range as well as the Levant, the Hadhramaut, and the east flank of the ‘Asir range in Saudi Arabia. Specimens from the Hajar Mountains have been designated as a distinct subspecies, C. microphthalmum mascatensis [6].
C. microphthalmum is a free-swimming fish with a streamlined body and a large, transparent, deeply forked tail. Individuals may be pale grey to mottled golden brown on top (smaller fish are better camouflaged), but when seen from the side they are a striking silvery white that may sometimes reflect like the flash of a knife blade. A dark yellow-black iridescent lateral line can be seen both in side view and from above. The individual body scales are prominent and have a dark outline, giving the pale sides a hachured appearance. The mouth is set forward but directed downwards. Close-up examination reveals a single pair of very thin barbels.
Adults are unmistakable, being larger than even the very largest G. barreimiae, up to an estimated maximum of 10-12 cm. Adults also exhibit a distinctive, elongated blue-white patch behind the eye as well as blue-white cheeks and lips, and sometimes blue-white pectoral fins. These colours appear to be independent of breeding status. In the aquarium setting breeding males are distinctly darker dorsally than females [5]. Young C. microphthalmum can be mistaken for young Garra barreimiae, with whom they are normally found. They are nevertheless relatively longer and thinner, golden rather than brown in colour, and they behave differently, swimming more continuously and without making contact with the bottom. C. microphthalmum is the least common of the native species and is normally absent from very small or shallow pools.
@
Aphanius dispar (Arabian killifish): The Arabian killifish is abundant in many UAE mountain wadis, but its primary environment is marine coastal lagoons and estuaries in around the Arabian Gulf, the Gulf of Oman and the Red Sea [6,7], where it may be the most common fish [10]. For this reason it is described as a “secondary” freshwater fish. Closely related species are found in similar environments throughout the Mediterranean and Asia Minor [6,7,16] and some other egg-laying toothcarps are kept as aquarium fish. Dispersal of the Arabian killifish from one wadi system to another is presumed to be aided by its ability to migrate along the seacoast, but this cannot satisfactorily explain its modern day presence in wadis on the west flank of the Hajar Mountains, far from the sea, except by reference to a much wetter climate in earlier times. This explanation has been invoked to explain the presence of many plants and animals, as well as most other freshwater fish, as relict species in isolated areas of the Arabian Peninsula, especially in the mountain regions of southern Arabia.
The Arabian killifish has been artificially introduced into certain UAE environments where fish would not otherwise occur, such as small agricultural runoff streams on the southern edge of the Ru’us Al-Jibal, and bulldozed ponds in coastal areas, where it has probably been introduced for mosquito control. This raises the possibility that it has been artificially introduced into some natural environments as well, although the author has not investigated the nature or extent of any such introductions.
The Arabian killifish is similar in size to most Garra barreimiae, adults being about 3.5-5.0 cm. Seen from above they are mottled golden brown in colour, always paler than any associated G. barreimiae. The tail is not forked, which can be the most useful feature in distinguishing smaller fish. The killifish typically swims somewhat higher in the water column than G. barreimiae, and may “hover” occasionally with the tail curved slightly to one side. The mouth is directed upwards and the killifish is a surface feeder by design, but in the wadi environment it is somewhat opportunistic. It may feed on the bottom from time to time, or scavenge dead insects, and it is known to eat mosquito larvae. The killifish has teeth in its jaws, which the other native fish do not.
Adult killifish exhibit marked sexual dimorphism. Males are pale and faintly white-stippled with a few vertical stripes near the tail. The tail fin itself is marked with 2-3 dark vertical bands which are diagnostic in the field. In breeding colour, the lips and fins are a vivid blue-white. The tail is fluttered like a matador’s cape when displaying to females. Mature females show numerous dark vertical bands like zebra stripes on the side of the body, although these markings are variable in detail.