Fishes of the Emirates

Abstract

Fishes are among the most diverse and abundant groups of animals in the United Arab Emirates (UAE) and support fisheries that are second most important economic resource in the UAE, after oil. Most fishes are found in the coastal waters, and several species even live in the freshwater pools and streams up in the mountain wadis. Fishes are most abundant in the Gulf of Oman and gradually decline in both abundance and diversity passing through the Strait of Hormuz and towards the southwestern region of the Arabian Gulf, mirroring the increasingly extreme environmental conditions. As fish in the southern Gulf experience extreme environmental conditions, such as high temperatures, that would kill fish from populations elsewhere in the world they are of great scientific value for understanding how fish and their communities might respond to climate change, with studies demonstrating the behavioural and physiological changes that result from these extreme conditions. Fishes in the Emirates are, however, heavily overfished and like fishes elsewhere vulnerable to climate change resulting in Arabian Gulf fish now being vulnerable to local extinction. While fisheries are now being managed to protect vulnerable species, further management is required to protect fish populations for future generations.

1 Diversity and Abundance of Fishes

Fishes are the most diverse vertebrate group with around 36,000 species, compared with 11,000 species of birds and 6500 species of mammals (IUCN 2021). Having evolved several hundred million years ago, fishes have diversified to the point they can be found in almost all major aquatic habitats on earth, from mountain to lakes to the depths of the oceans, under the ice of the polar seas, intertidal mudflats, the darkest caves, and everything in between. Indeed, fishes are ecologically dominant in most aquatic habitats where they are found and play a central role in maintaining the functioning and health of their various ecosystems (Helfman et al. 2009). Fishes also represent a valuable resource for humanity, providing 178 million tonnes of food globally at a value of USD 406 billion (2020 data; FAO 2022). It is of little surprise that fishes are an important economic and ecological resource in the United Arab Emirates (UAE), second only to oil in terms of economic value as a resource sector (van Lavieren et al. 2011).

The UAE is predominantly a desert, yet freshwater habitats do exist and consist of pools and streams in the wadis of the Hajar Mountains as well as in various man-made dams, wells and related structures. However, most of the UAE’s aquatic environments are marine, and encompass 58,000 km² across the national exclusive economic zone, including both the Arabian Gulf and the Gulf of Oman. Overall, approximately 479 species of fish from 95 families are reported to inhabit the marine and brackish waters of the UAE (Froese and Pauly 2022), with an additional 3 species being freshwater (Freyhof et al. 2020) (‘fish’ refer here to ‘bony fishes’, not cartilaginous fishes (e.g. sharks and rays) which are discussed separately in Chap. 20). Freshwater fishes are discussed separately in Box 21.1, with the remainder of the chapter focused on marine fish assemblages.

Several fish families dominate in terms of the number of species and total abundance in the UAE, with the trevallys and jacks (Carangidae), tuna (Scombridae), snapper (Lutjanidae), and seabreams (Nemipteridae) families being particularly diverse and abundant, along with some families of smaller fishes that are closely associated with coral reef systems, including wrasses (Labridae), blennies (Blenniidae), gobies (Gobiidae) and cardinal fish (Apogonidae). Among this diverse group are species that highlight the marked variety of fishes, with members of the Gobiidae family being just a few centimetres in length while ocean sunfish (Fig. 21.1c; Mola mola) are the largest bony fish in the world. Some species, on the other hand, such as the spotted seahorse (Hippocampus kuda), the stonefish (Synanceia verrucosa) and humpback turretfish (Fig. 21.1f; Tetrosomus gibbosus) defy expectations of what a fish should look like.

Fig. 21.1

The UAE is home to diverse array of fish species. (a) Broomtail wrasse (Cheilinus lunulatus), (b) Arabian butterflyfish (Chaetodon melapterus), (c) Ocean sunfish (Mola mola), (d) Sailfish (Istiophorus platypterus), (e) Yellowtail tang (Zebrasoma xanthurum), (f) Humphead turretfish (Tetrosomus gibbosus), (g) Moon wrasse (Thalassoma lunare), (h) Flathead grey mullet (Mugil cephalus), (i) Picasso triggerfish (Rhinecanthus assasi), (j) Yellowfin tuna (Thunnus albacares), (k) Dory snapper (Lujanus fluviflamma), (l) Painted sweetlips (Diagramma pictum). Photo credits: (a) Cheilinus_lunulatus...DSCF8074BE.jpg by Kora27 (CC BY-SA 4.0); (b) IMG_3683.JPG by Parviz Tavakoli Kolour (CC-BY 3.0); (c) modified from Mola mola géant Bali.JPG by Franck Fauvel (CC BY-SA 3.0); (d) 8063763187_f18b7f7e96_o by CFoceanimages (CC BY-ND 2.0); (e) Zebrasoma xanthurum2.JPG by Gdiggers (CC BY-SA 3.0); (f) Humpback Turretfish – Tetrasomus gibbosus.jpg by Bernd (CC BY 2.0); (g) Thalasoma lunare 1.jpg by Leonard Low (CC BY 2.0); (h) Mújol (Mugil cephalus), Parque natural de la Arrábida, Portugal, 2020-07-23, DD 19.jpg by Diego Delso (CC BY-SA 4.0); (i) Picassofish_(a_triggerfish),_Rhinecanthus_assasi_(35735682754).jpg by Derek Keats (CC BY 2.0); (j) Al mcglashan tuna.jpg by Al McGlashan (CC BY-SA 4.0); (k) Lutjanus_fulviflamma.jpg by Erics (CC BY-SA 4.0); (l) Painted_Sweetlips_(Diagramma _pictum)_subadult_(8501952361).jpg by Bernard Dupont (CC BY-SA 2.0)

When compared to other regions at similar latitudes within the Indo-Pacific, the diversity of UAE fishes is lower than expected and several taxonomic groups that are common elsewhere are missing from this region (Carpenter et al. 1997; Coles and Tarr 1990). This lower diversity reflects the biogeographic isolation of the UAE and extreme environments found in its waters (Burt et al. 2011; Grandcourt 2012; Sheppard 1993). The UAE is situated in the far northwest corner of the Indian Ocean and is isolated by a range of environmental and oceanographic barriers that minimise the influx of new species from the adjacent Red Sea, western Indian Ocean, and Indo-Pacific regions (Burt et al. 2011; Grandcourt 2012). Consequently, the Gulf of Oman and Arabian Gulf fish communities represent distinct biogeographic subregions, home to progressively more depauperate fish communities. The diversity and abundance of fishes is highest in the Gulf of Oman. This is due to its proximity to the Arabian Sea, from where the majority of the UAE fishes originated, but also due its high productivity due to upwelling of deep, nutrient rich waters during the summer monsoon, and the relatively benign environment, where temperatures range from 22 °C in the winter to 32 °C in the summer, while salinity hovers around 36 PSU which is typical of open ocean systems (Reynolds 1993; Sheppard et al. 1992). In contrast, the Arabian Gulf is young, only forming around 16,000 years ago following the last ice age, and only reaching its current shorelines 6000 years ago (Sheppard et al. 1992) (see Chap. 4 for further details on the Gulf’s origin and environment). Due to being formed only recently, endemic species have had little time to evolve and there are no species endemic to the Arabian Gulf alone (Froese and Pauly 2022), although a few Gulf species are endemic to the broader Arabian region (DiBattista et al. 2020). Consequently, the diversity of fishes in the Arabian Gulf has been dependent on the colonisation of species from the Gulf of Oman via the narrow Strait of Hormuz. Furthermore, those species that made it into the Arabian Gulf must be able to survive the extreme environmental conditions of the southern Arabian Gulf where most of the UAEs marine area occurs. The southern Arabian Gulf is very shallow (<30 m deep) and experiences extreme environmental conditions, with temperatures ranging from 12 °C in winter to >36 °C in summer, hyper-saline conditions (~44 PSU) and periods of low oxygen (hypoxia) and near-absence of oxygen (anoxia) during summer months (Sheppard et al. 1992; de Verneil et al. 2021). As a result, as shown in Fig. 21.2, the diversity and abundance of fish declines as you move into the Arabian Gulf and environmental conditions get progressively more challenging towards the southwest (Burt et al. 2011; Feary et al. 2010).

Fig. 21.2

A 2019 survey of fishes in the southern Arabian Gulf shows both the diversity and abundance of fish clearly declines from the Strait of Hormuz moving into the more environmentally extreme southern Arabian Gulf. The location of the reef surveyed are shown on the map while the total number of species recorded (blue bars) and the average abundance of fish (orange bars) are shown in the graph. Image credit: Google Earth Pro version 7.3, (2017) UAE coastline 25°27′15.61″N, 54°41′18.09″E . 3D buildings data layer. [Online] Available at: http://www.google.com/earth/index.html [accessed 10/07/2022]; Data Source: Matthew Mitchell, unpubl. Data.)

Box 21.1 The Freshwater Fishes of the Hajar Mountains and Coastal Systems

Three species of freshwater fishes are native to the UAE. Two species, the Hajar Lotak (Cyprinion muscatense) and Orange-ear Garra (Garra barreimiae) are within the family Cyprinidae (barbels and carps) and are restricted to the freshwater streams and pools of the Hajar Mountains. A single salt-tolerant species, Arabian killifish (Aphaniops stoliczkanus) from the family Aphanniidae (Eurasian killifish) is found in both coastal and freshwater bodies.

Hajar Lotak—endemic to the Hajar Mountains, which are shared between Oman and UAE, with the latter being the most northern distribution range for the species globally. Within the UAE, the species is restricted to a small geographical area near Hatta (Dubai). It is found within larger pools with seasonal fluctuations in discharge. A fast-moving and mid-water dweller which form small schools, the Hajar Lotak feeds on periphyton as well as aquatic and terrestrial invertebrates. Adult fish are 134 mm in size and spawn for the first time at 8–13 months of age. There is no specific spawning season, but is likely triggered by the rain season. During the spawning season, adults develop a prominent light blue colour on the head, lips and pectoral fin.

Box Fig. 21.1 Hajar Lotak (Cyprinion muscatense) from the Hajar Mountains. Photo credit: Johannes Els 

Orange-ear Garra—endemic to the Hajar Mountains within Oman and United Arab Emirates. It is found within pools, streams, falaj systems and springs with fresh or brackish waters along both flanks of the northern Hajar Mountains, extending southwards from the southern edge of the Ru’us al-Jibal range (Musandam peninsula) to the Sultanate of Oman border. The species distribution range extends into the Sultanate of Oman to Wadi Hawasina on the Gulf of Oman coast. Adult fish are 70 mm in size. Orange-ear Garra are opportunistic feeders consuming periphyton, dead insects and decaying plant materials. The Orange-ear Garra can survive under extreme conditions and can withstand very high temperatures, fluctuating salinities and seasonal flash floods. Unique adaptations include a reduced air bladder to lessen buoyancy and an adhesive structure (mental disc) which with the assistance of their large, paired fins maintain their position in fast flowing waters.

Box Fig. 21.2 Right: Orange-ear Garra (Garra barreimiae) from Wadi Shawka. Left: Ventral view of the adhesive structure behind the lower jaw of the Orange-ear Garra. Photo credit: Johannes Els

Arabian killifish—A widespread coastal species from the shores of north-West India, Iran, Iraq, Kuwait, eastern Saudi Arabia, UAE and Gulf of Oman. It is found in lagoons, estuaries, lower parts of streams and in a variety of inland water bodies. Within the Hajar Mountains they are restricted to lower pools and streams and are absent from the uppermost mountain pools where only Orange-ear Garra are present. Arabian killifish were widely introduced into water bodies throughout the country, most likely to aid in the control mosquito larvae. Adult fishes are 53 mm in size. Females, juveniles and non-reproductive males form shoals in open water. Adult and reproductive males are territorial and during spawning season defend spawning sites. Males grow larger than females with a lifespan of 2–3 years. A male and female will pair up for spawning on plants, algae and in rock fissures. The species can tolerate salinities up to 14.5‰ and for short periods up to 25.0‰. Arabian killifish feed on algae, detritus and a variety of aquatic invertebrates.

Box Fig. 21.3 Arabian killifish (Aphaniops stoliczkanus). Photo credit: Barbara Nicca

2 Fish Habitats of the Emirates

2.1 Natural Habitats

The benthic (i.e., sea bottom) environment of the UAE primarily consists of soft sediments with little to no structural complexity on either coast. Yet this structurally benign environment supports a matrix of interconnected habitats that provide critical resources for fishes throughout their lives. Many of these habitats are located within the intertidal and subtidal areas adjacent to the coast (Fig. 21.3a, b; Mateos-Molina et al. 2020, 2021; Vaughan et al. 2019). These habitats are highly productive and support a greater diversity and abundance of fishes in coastal waters than in offshore regions, particularly in the Arabian Gulf (Egerton et al. 2018; Lin et al. 2021), and are far more diverse than the neighbouring terrestrial environment (Van Lavieren et al. 2011).

Fig. 21.3

Fish have colonised all marine habitats in the UAE including intertidal (a) mudflats and (b) mangroves which they access during high tide, as well as subtidal (c) seagrass beds and (d) coral reefs. Photo credits: (a, d) Matthew Mitchell and (b, c) Noura Al-Mansoori

Fringing the coastline, intertidal habitats, which include salt flats (sabkha in Arabic), mangrove forests, and mudflats are particularly productive and provide important feeding grounds for fish. These intertidal habitats have a very shallow gradient (in the UAE), cover large areas, and provide substrate for extensive algae mats (Barth and Böer. 2002; Burt 2014). In turn, the algae support a diverse invertebrate community on which fish can feed during high tides. As these sites are only accessible periodically during high tide and provide shelter via mangrove root systems and in the pools and drainage channels during low tides, they provide important nursery grounds for a range of fishes such as juvenile sweetlips, snappers, and mojarras (Fig. 21.4; Barth and Böer 2002; Burt 2014). The only fish able to live permanently in these habitats are Walton’s mudskippers (Periopthalmus waltoni) which even inhabit mangrove areas during low tide when water is out (Feulner and Roobas 2013). These unusual fish are amphibious and can survive for extended periods out of the water by breathing through their skin.

Fig. 21.4

Intertidal habitats provide shelter for juvenile fish from larger predators. (a) shallow pools and channels in mangroves allow juveniles to avoid predators during low tide, while at high tide the above ground roots provide shelter. (b) Juvenile sweetlips hide in a shallow mangrove pool. Photo credits: Matthew Mitchell

Adjacent to these habitats, subtidal habitats are dominated by extensive seagrass beds, seasonal macroalgal beds and coral reefs (see Chaps. 9, 10, and 11, respectively) (Fig. 21.3c, d; Vaughan et al. 2019). Coral reefs are by far the most productive and important habitat for fishes in the UAE. The complex structure provided by corals support highly biodiverse fish communities, including most species found in the UAE. For example, 280–300 of the 540 species (incl. sharks and rays) in the Gulf of Oman (ca. 55%) are reef-associated fishes (Bento 2009). Indeed, the abundance of fish on coral reefs is such that reef-associated fish contribute 70% of fisheries catches within the Arabian Gulf (Grandcourt 2012). Seagrass beds cover an area of 5500 km² in the UAE representing 4% of the total seagrass habitat in the world. They are also considered to be the second most diverse habitat in the UAE following coral reefs, and they support a range of commercially important fish species (Basson et al. 1977). Macroalgal beds are seasonally abundant and reach their peak during spring where they can cover up to 85% of available hard substrate, creating a complex new habitat for fishes (John 2012). Yet, while it is thought they provide important spawning and nursery habitats for fishes (Sheppard et al. 1992), macroalgae is a poor food source for most fishes and is eaten by only a few species (Sheppard et al. 2010). It has also been suggested that the proliferation of macroalgae on reefs during the winter and spring period may have a negative effect on reef fish abundance (Coles and Tarr 1990; Grandcourt 2012), a pattern seen on reefs in Australia where fish actively avoid dense algae patches (Hoey and Bellwood 2011).

Offshore pelagic (i.e., deep) waters, while less diverse in terms of habitats compared to coastal waters, are by far the largest in terms of area and include limestone mounds and salt domes which can form islands with fringing coral reefs. While these offshore waters support a lower diversity and abundance of fishes, they still maintain important fisheries and provide critical support for a range of species (Egerton et al. 2018; Lin et al. 2021). Recent studies have shown that for several pelagic species, adults tend to be more abundant offshore and some species such as sailfish (Istiophorus platypterus) and mackerel tuna (Euthynnus affinis) migrate from inshore to offshore waters in the spring to breed (Hoolihan 2003, 2004; Hoolihan and Luo 2007; Robinson et al. 2013). As with inshore habitats, fishes tend to be associated with the more complex habitats such as oyster beds and coral reefs (Egerton et al. 2018; Lin et al. 2021). This is particularly true around offshore islands such as Sir Abu Nu’Ayr, where extensive coral reefs host a higher abundance and diversity of fishes due to being surrounded by cooler deeper waters compared to their inshore equivalents (Burt et al. 2016; Sheppard et al. 1992).

Beyond these broad gradients in fish abundance resulting from environmental and biogeographic conditions, there is little information as to how and why fishes are distributed across the various habitats of the UAE. Most fish species are highly mobile and move between different habitats depending on their resources requirements or to avoid deleterious environments. This is done over temporal scales including diurnal, seasonal or at critical junctions in their life-histories (e.g., for spawning, or transitioning from juvenile to adult habitats) (Clark et al. 2009; Dahlgren and Egglestone 2000; Mumby and Hastings 2007). In doing so, they act as important vectors for transporting nutrients and energy between these different habitats (Clark et al. 2009; Sheaves 2009). In tropical coastal systems mangrove forests, seagrass beds and coral reefs have been shown to be highly connected due to fish movements, where juveniles recruit to seagrass beds and mangrove forests before moving to coral reefs as adults (McMahon et al. 2012; Mumby et al. 2004). Yet the ecological value of the UAE aquatic habitats for fish and the connectivity between them is still to be determined. However, many fishes in the UAE do appear to move between different habitats, e.g., pelagic species like sailfish (Istiophorus platypterus) are thought to migrate offshore to breed (Hoolihan 2003; Hoolihan and Luo 2007). Coastal habitats appear to be important nursery grounds (Burt 2014; Vaughan et al. 2019), but their relative value as such remains unknown, and knowledge of where fish go once they leave these habitats is also unknown. Possibly the most striking movement of fishes between habitats occurs on coral reefs, where seasonal abundance of fish can vary by 40%, with fish numbers peaking during the hottest summer months (Vaughan et al. 2021). Again, where and why these fishes leave the reefs during the winter months has still to be determined. Studies have suggested fishes move offshore to avoid colder waters in the shallows (Coles and Tarr 1990), while others argue that fish may not leave at all and are just less active and therefore less visible during cold spells (Vaughan et al. 2021).

2.2 Artificial Habitats

Following the discovery of oil and gas in the region, the human population has expanded rapidly over the last few decades with an increasing amount of people moving to coastal cities in the UAE. Consequently, there has been a rapid acceleration of coastal development to the point where breakwaters and seawalls form extensive marine habitats in urban areas (see Chap. 23) (Burt et al. 2012, 2013b; Burt 2014). Further offshore, structures pertaining to the oil and gas industry provide complex, novel habitats in what is mainly a low complexity, sand-bottom environment. These structures rapidly develop marine assemblages, and act as large-scale unplanned artificial reefs. Similarly, more typical planned artificial reefs have been built with the aim of attracting species for fisheries and tourism (Feary et al. 2011), and diverse communities rapidly develop around them as well (Burt et al. 2009; Feary et al. 2011). Surveys of fish communities in these habitats have revealed that densities of fish can exceed those on local reefs, including commercially important species such as snappers, groupers, jacks, and barracudas (Al-Cibahy et al. 2009; Burt et al. 2010). While these various human-made structures support large communities of fishes, their ecological value and role towards population productivity are poorly understood (Feary et al. 2011). A study of breakwater fish communities in Dubai showed that fish species composition differed from those on local coral reefs (Burt et al. 2009). Furthermore, seasonal changes in abundance and diversity did not match natural fluctuations observed on coral reefs (Burt et al. 2010), suggesting that artificial habitats are not surrogates for natural habitats. However, there is evidence that human-made reefs can maintain key ecological roles, as juvenile fish colonise breakwaters in similar numbers as they do on coral reefs (Burt et al. 2010) and mackerel tuna (Euthynnus affinis) aggregate under oil rigs during spring and possibly use them as spawning sites (Robinson et al. 2013) (Fig. 21.5).

Fig. 21.5

With the rapid increase in coastal development and the petroleum industry, fishes have learned to use these artificial habitats as novel homes. (a) underwater structures of oil rigs are home to many fishes, (b) seawalls are common along the UAE coastline, (c) fishes including snapper and seabreams are regularly seen along these structures. Photo credits: (a) Mubarek Offshore Platformes.jpg by Crescent Petrolium/Icethorn (CC BY-SA 3.0); (b, c) Matthew Mitchell

3 Ecology of Fishes on the World’s Hottest Reefs

Fishes are central to the ecological functioning of marine habitats, and through their various behaviours and activities, they maintain ecosystem health and support marine food webs. Our understanding of the ecology and demography of fishes in the waters of the UAE is rather rudimentary. Few studies over the years have directly examined fish ecology and much of what we know is based on fisheries trawls, which are subject to bias from gear selectivity that targets commercial species (Grandcourt 2012). However, over the last 15 years or so, there has been a significant increase in ecological studies focusing on the impacts of the extreme environment in the southern Arabian Gulf on coral reef fish communities. Extremes in temperature, dissolved oxygen, and salinity pose significant physiological challenges to fish, impacting neurological function, inducing deleterious stress effects, and impacting energy budgets which in turn can impact growth, reproduction, survival, population dynamics and, ultimately, the structure and functioning of communities (Munday et al. 2008; Pankhurst and Munday 2011). The variation in environmental conditions within the UAE, and particularly between the two Gulf regions, provides a unique ‘natural laboratory’ for comparative studies on how fish communities persist under the extreme environmental conditions seen in the southern Arabian Gulf.

Studies into the life-history traits of fishes in the UAE have largely focused on commercially important species such as orange-spot grouper (Epinephelus coioides), Spangled emperor (Lethrinus nebulosus), Painted sweetlips (Diagramma pictum), and the Dory snapper (Lutjanus fulviflamma) (Grandcourt et al. 2011a; Grandcourt 2012). Such studies show that fishes within the UAE vary greatly in their age and growth characteristics, but certain global life-history trends persist e.g., shorter lived species tend to grow much faster than the more long-lived species (Grandcourt 2012). What is also apparent is that fishes in the southern Arabian Gulf along the Abu Dhabi coast tend to be smaller at a given age, reach smaller maximum size, and are younger than individuals from other locations in the Arabian Gulf and Gulf of Oman (Grandcourt et al. 2011a; Grandcourt 2012; Priest et al. 2016). For example, the maximum size of Yellowfin hind (Cephalopholis hemistiktos) caught in Abu Dhabi was just 288 cm compared to 443 cm in the Gulf of Oman (Priest et al. 2016). These differences in life-history traits conform to those of stocks that are overfished, which tend consist of smaller fish that reproduce earlier (Grandcourt et al. 2011a; Grandcourt 2012). However, recent studies on non-commercial species suggest that environmental conditions may also be having an effect on fish life-histories (Brandl et al. 2020; D’Agostino et al. 2020, 2021). These studies have shown that in the southern Arabian Gulf, fishes, including tiny cryptobenthic fishes, are smaller than their counterparts in other regions of the UAE, although age does not seem to differ between locations (Fig. 21.6; Brandl et al. 2020; D’Agostino et al. 2021; Feary et al. 2010). The reduction in size of these fishes has generally been ascribed to the extreme summer temperatures of the southern Arabian Gulf limiting the energy available for growth (Brandl et al. 2020; Feary et al. 2010). Additionally, a recent study suggested that salinity was in fact the primary cause of smaller sized fishes, as osmoregulation can require up to 30% of a fish’s daily energy production (D’Agostino et al. 2021). Indeed, there is growing evidence that despite exceeding the upper thermal limits of fishes elsewhere in the world, the extreme temperatures of the southern Arabian Gulf are within the range of tolaerance of many species from either of the UAE’s coasts (Brandl et al. 2020; D’Agostino et al. 2021). Research investigating the impacts of the extreme environments on fish physiology and life-history are only in their infancy in the UAE, but it is likely that both environmental stressors (for all fishes) and overfishing (for larger fishes) contribute to changes seen in fish life-history traits.

Fig. 21.6

Growth curves for Blackspot snapper (Lutjanus ehrenbergii) (upper graph) and Yellowbar angelfish (Pomacnthus maculosus) showing the greater sizes reached for fish populations in the Gulf of Oman (blue lines) compared to the hotter and more saline Arabian Gulf (red lines). Image credits: Modified from Fig. 3 in D’Agostino et al. (2021), reproduced under Creative Commons (CC-BY-4.0)

Beyond the impacts on life-history traits, temperature appears to have a profound effect on the ecology of fishes in the southern Arabian Gulf. Observations of Paletail damsels (Pomacentrus trichrourus) on coral reefs around Abu Dhabi have shown that these fish modify behaviours to mitigate the effects of temperature (D’Agostino et al. 2020). Both laboratory and field studies demonstrated damsel foraging rates, activity and distance moved were kept to a minimum when thermal stress was at its highest in both winter and summer, but feeding activity peaked during spring when thermal stress was minimal (D’Agostino et al. 2020). Such plasticity in behaviour is thought to reflect either the physiological constraints of temperature on the performance of ectotherms or behavioural optimisation of energy expenditure versus energy acquisition. Diet also appears to vary within species on geographical and seasonal scales. A range of fishes have distinct diets between Gulf of Oman populations and the southern Arabian Gulf populations, with Yellowbar angelfish (Pomacanthus maculosus) switching from primarily feeding on sponges and algae across most its global range to eating live coral on reefs around Abu Dhabi (Shraim et al. 2017), while cryptobenthic species eat a greater diversity of prey in the Gulf of Oman compared to Arabian Gulf populations (Brandl et al. 2020). This plasticity in diet choice also occurs across seasons, with Paletail damsels and Dark damsels (Pomacentrus aquilus) both consuming a diverse array of prey during the spring months of April and May before switching to feeding predominantly on corals during the hottest month of August (Shraim et al. 2017). It is unclear if these changes in diet reflect active selection for foods with different nutritional values in response to changing temperature, selection for food based on what is available across seasons, or simply what they are able to physically capture and consume during the hottest months (Shraim et al. 2017). What is clear, however, is that with increasing temperature, the quality and volume of food consumed by fishes declines (Brandl et al. 2020; D’Agostino et al. 2020; Shraim et al. 2017). Consequently, Arabian Gulf individuals tend to be of poorer body condition than their counterparts in cooler environments such as the Gulf of Oman, and the seasonal variation of food quality likely contributes to variable growth patterns seen in many fishes from the southern Gulf. Additionally, the lower productivity of these smaller fish will have a negative effect on the transfer of energy and nutrients through higher trophic levels (Brandl et al. 2020). This is particularly true for the cryptobenthic communities which are thought to be a major food source that support reef fish communities (Fig. 21.7; Brandl et al. 2019). Extreme temperatures may, therefore, act to constrain the ability of coral reef ecosystems to maintain abundant and diverse fish communities indirectly via declines in abundance and/or quality of food resources available on reefs.

Fig. 21.7

Cryptobenthic fishes are small (<5 cm length), often camouflaged and with a tendency to hide, and consequently they are generally overlooked. Yet they actually make up around half the number of fish on coral reefs and play and important role in supporting reef communities. As they are fast growing and short lived, with several generation per year, it is thought they provide the major food source that sustain fish communities on coral reefs (Brandl et al. 2019); (a) Anomalous goby (Coryogalops anomalus), (b) Lemon goby (Gobiodon citrinus), (c) Gulf blenny (Ecsenius pulcher), (d) S tarry goby (Asterropteryx semipunctata) Photo credits: (a, c) Matthew Mitchell; (b) Lemon_Goby.jpg by Rob (CC BY 2.0); (d) HoshiHZro.jpg by Izuzuki (CC BY-SA 3.0)

These environmental effects on fishes appear to drive community level changes on coral reefs, as communities in the southern Arabian Gulf have low abundance of most trophic guilds (i.e. feeding groups, for example ‘herbivores’) compared to reefs in less extreme regions in the UAE (Burt et al. 2011; Feary et al. 2010). Reef fishes in the southern Arabian Gulf are predominantly made up of grazing herbivores, omnivores, and small generalist predators while several important groups such as large herbivores, corallivores, planktivores and species closely associated with coral are rare or missing entirely (Burt et al. 2011). Many of these important functional groups perform key services that maintain the diversity and functioning of reefs, none more so than large herbivores such as parrotfishes (Hoey et al. 2016). Parrotfishes are the most important guild of herbivores, making up the majority of ‘scraper’ and ‘excavator’ fishes that are responsible for removing algae from the reef, clearing ground for coral juveniles to settle and grow. In the absence of these herbivores, and with low abundance of sea urchins, it is not clear which processes control algal communities on these reefs (Hoey et al. 2016). Corallivores are also usually well represented within coral reef communities globally, but are rare throughout the UAE, where only five species are present, most of which are generalists rather than the specialists that are common elsewhere (Pratchett et al. 2013). In the southern Arabian Gulf, they are represented by just one species, the Black-spotted butterflyfish (Chaetodon nigropunctatus). That corallivores are rare here would suggest there is no link between corals and higher trophic groups on these reefs (Pratchett et al. 2011, 2013). However, recent studies on the diets of fishes in the southern Arabian suggest that the functional role of specialist corallivores might be fulfilled by other species switching to more generalist diets, as both damselfishes and angelfish have been shown to consume significant amounts of coral rather than their normal diets of plankton, algae and sponges (D’Agostino et al. 2020; Shraim et al. 2017).

4 Fisheries in the UAE

Fishes have played a central role in the history of coastal communities of southeast Arabia. With deserts covering much of the terrestrial environment, fishes have historically provided an important source of food and valuable commodity for trade (Beech 2003). The earliest records of fishing activity in the region date back to 8000 YBP, during the Neolithic period, when fishers predominantly caught species found in shallow waters associated with mangroves and seagrasses (Lidour and Beech 2019, 2020). The presence of stone sinkers in settlements suggests that beach seines and gill nets, along with hadrah’s (Fig. 21.8a; semi-permanent tidal barriers traps) were the main methods used to capture fish (Beech 2003; Lidour and Beech 2020). Gargoor’s (Fig. 21.8b; baited basket traps made from palm fronds) were also likely to have been employed, although being made from palm fronds there is little evidence for their use due to their poor preservation (Lidour and Beech 2019, 2020). Fish bones found at UAE archaeological sites have revealed that neolithic communities ate a diverse variety of fish species not too dissimilar from the species targeted by modern fisheries, with seabreams, emperors, anchovies, tuna, groupers and sweetlips being the main species caught, along with small sharks and sawfish commonly captured (Fig. 21.8d, e; Lidour and Beech 2020).

Fig. 21.8

The communities inhabiting the northeast Arabian Peninsula have been fishing since Neolithic times using many techniques still used today, including (a) Hadra, intertidal fence traps. Today fish are still caught using traditional boats (b) Dhow’s and many of the species sold in (c) local markets have remained the same as caught by people during the Neolithic period , such as (d) hammour and (e) jesh. Photo credits: (a) Shamsa Al-Hameli; (b, c) Matthew Mitchell; (d) Noura Al-Mansoori; (f) 46864187155_7a7040181c_o Rickard Zerpe (CC BY 2.0)

Today, fishes still represent an important source of nutrition and trade in the UAE. While revenues from commercial fisheries account for only a modest portion of the UAE’s GDP (Wabnitz et al. 2018), it is nonetheless the country’s second most valuable natural resource following oil and gas (Grandcourt 2012). In the emirate of Abu Dhabi alone, 1267 tonnes of fish were landed in 2020, generating a revenue of 24.4 million Dirhams (EAD 2020). Fishing is still an important part of the Emirati cultural heritage, cuisine and a popular sport, and healthy fish stocks are therefore of national importance. Typically, modern fisheries operate from traditional wooden dhow boats (Fig. 21.8c; lansh) fitted with engines, with fishing trip duration averaging around 3–5 days (Grandcourt et al. 2009). The current contribution of lansh  (small boats launched from land) to total landings has however steadily decreased since the introduction of recent fishing restrictions (Environment Agency Abu Dhabi 2020). Some fishers hold privileged concession rights to fish in private areas (known as buhoors) and the right to use restricted fishing methods (Environment Agency Abu Dhabi 2020). These rights are passed on through generations in an effort to conserve cultural elements of the UAE maritime way of life.

Overall, fish catches are diverse, and reef-associated species form the bulk of all fish landings, with the key species encountered at fish markets dominated by emperors, groupers, sweetlips, jacks, trevallys, snappers, mackerels and seabreams (Grandcourt 2012). The total fish landing volume is largely represented by four valuable species: the Narrow-barred Spanish mackerel, the Orange-spotted grouper, the Blackspot snapper and the Orange-spotted trevally. Gargoors have traditionally been the most used technique to non-selectively target demersal (bottom-dwelling) species but were banned in 2019 in the emirate of Abu Dhabi due to concerns over declining fish stocks. Other techniques currently in use include hadrah, gill nets, barrier nets, beach seines and handlines (Grandcourt 2012; Grandcourt et al. 2009). Due to supply and demand imbalances, the UAE is an active seafood importer, with 72% of consumed seafood originating from other countries and the local fisheries and aquaculture operations supplying the remaining 28% of consumed seafood (Environment Agency Abu Dhabi 2019; Jawan and Waryani 2021).

5 Threats to the Persistence of Fishes in the UAE

As fishes are both ecologically and economically important to the UAE, they are susceptible to both changes in their environment and over-exploitation from commercial fisheries. Fishing practises, in particular, have led to significant declines in fish populations. In the Arabian Gulf 47% of marine bony fishes are impacted by extractive fishing and 8.2% of fish species are classified as ‘threatened’ as per the IUCN Red List standard (Buchanan et al. 2019). Fishing intensity has climbed over the last 30 years (Vaughan et al. 2019), with areas of low fish abundance converging with zones of high human population density, thus further highlighting the increasing strain on renewable but finite resources (Grandcourt et al. 2011b). Traditional inshore fisheries are thought to operate within sustainable levels owing to the use of non-destructive methods and the implementation of fish catching permits; however, very little data is available on actual recreational catches (Jawad and Waryani 2021). On the other hand, most commercial fisheries are currently classified as fully exploited or over-exploited, with declines in abundance seen across most fish stocks (Grandcourt 2012). Furthermore, by targeting specific size-classes of fish (typically the largest), fisheries can disproportionately impact demographics of fish populations reducing their capacity to reproduce and replenish stocks (Grandcourt 2012).

The rapid growth of the population of the UAE following the development of the petroleum industry has resulted in the urbanization of coastal regions, to the point that 40% of the Arabian Gulf’s coastline has now been modified to accommodate these growing populations (Naser 2014). Processes such as dredging and land reclamation to build these projects has resulted in considerable damage to and loss of coastal habitats, which have either been built directly on or smothered by dredged material (Fig. 21.9; Burt 2014; Feary et al. 2011; Vaughan et al. 2019). The loss of these habitats places addition stress on what are productive but threatened habitats that support fish populations. Furthermore, to sustain the human population of the UAE in this arid environment, numerous desalinations plants have been built throughout the UAE to provide potable water (Sale et al. 2011). The production of this water results in over 1000 m³/s of waste brine, water that is both higher in salinity and (often) temperature than the surround water, being pumped into coastal waters producing plumes that can extend several kilometres (Burt et al. 2013a; Hamza and Munawar 2009). These plumes not only represent a significant additional physiological challenge for fish osmoregulation in an already thermally and osmotically challenging environment (D’Agostino et al. 2021) but toxins in the form of heavy metals, chlorates and radioactive isotopes might, along with those from wastewater discharge explain the increasing levels heavy metals found in fish (Vaughan et al. 2019).

Fig. 21.9

Coastal development has led to the destruction of significant areas of coastal habitat. (a) The Dubai coastline is heavily developed and consists of sea walls, harbours, and offshore developments such as the manmade islands of (b) the World Islands and (c) the Palm Jumeirah. Image credits: (a) Google Earth Pro version 7.3, (2017) Dubai coastline 25°04′33°N, 55°13′38″E. 3D buildings data layer. [Online] Available at: http://www.google.com/earth/index.html [accessed 13/07/2022]; (b) Google Earth Pro version 7.3, (2017) The World Islands 25°13′30″N, 55°09′57″E. 3D buildings data layer. [Online] Available at: http://www.google.com/earth/index.html [accessed 13/07/2022]; (c) Google Earth Pro version 7.3, (2017) Palm Jumeirah 25°07′11″N, 55°07′50″E. 3D buildings data layer. [Online] Available at: http://www.google.com/earth/index.html [accessed 13/07/2022]

Climate change poses a significant threat to fishes throughout the UAE. While fishes in the Arabian Gulf already live at temperatures above those predicted to kill fishes elsewhere in the world by 2100, they are still susceptible to further increases in temperature and are likely living at the upper limits of what they can physiologically tolerate. The frequent fish kills seen in coastal waters during the hottest periods in summer would certainly suggest this is the case (Al-Ansi et al. 2002). As discussed earlier, temperature is already impacting fishes living in the hotter areas of the UAE, and with temperatures increasing in the Arabian Gulf at twice the rate of global oceans (Al-Rashidi et al. 2009), we can expect to see these effects exacerbated in the future and extend to Gulf of Oman populations as well. Fishes will also be indirectly affected by climate change through habitat degradation and loss. Coral reefs, in particular, will be affected by climate change as corals, which build the structure of reefs and provide food for many species, experience ‘bleaching’ events and often die during periods of high temperatures (see Chap. 11). If not replaced by new corals, this can lead to the erosion of reef complexity as well as loss of food resources that supports fish communities (Munday et al. 2008; Pratchett et al. 2009). These bleaching events have already happened on UAE reefs in 1996 and 1998 when 90% of corals were killed, and in 2017 when 73% of corals were lost (Burt et al. 2019; Riegl 2002). As a result, important structure-forming corals like table corals (Acropora) are no longer found on inshore reefs in the southern Gulf and are becoming rare on the east coast of the UAE. Indeed, with continued habitat loss and fragmentation, along with the effects of climate change, most of the UAE’s fishes will be vulnerable to extinction within the coming decades (Buchanan et al. 2019).

6 Management and Conservation

While it may seem that the future is bleak for the UAE’s fishes, steps are being taken by the government to reduce the impacts on fishes and to protect them for future generations. Given the various pressures on fish populations, management effort are being applied through two main avenues: management of fisheries and the protection of key habitats. Regulation of fisheries has been steadily increasing since the turn of the century, with increased monitoring followed by progressively more stringent restrictions on fishing gear. Fisheries resource assessments, complemented with traditional knowledge surveys, are now regularly conducted by the relevant government and environmental agencies to assess the exploitation levels of commercially important species (Grandcourt et al. 2009). Alongside this increased monitoring, various restrictions on gear use are being promoted, with bans on trawling and fishing gear such as drift nets, gill nets and gargoors implemented to protect sensitive habitats. Similarly, seasonal closures and species-specific catch permits have been enacted to protect over-exploited species and species vulnerable at certain times of year (e.g., spawning periods) (EAD 2020).

Throughout the emirates a series of Marine Protected Area (MPA) networks have been developed to protect fishes and their habitats, including in the Arabian Gulf (10 MPAs) and Gulf of Oman (5 MPAs) (IUCN 2022). Around 12% of the UAEs marine environment is now protected in these areas, many of which are located in Abu Dhabi and are showing promising signs of ecological recovery (Grandcourt et al. 2011b; IUCN 2022). Reports have noted increased abundance, biomass and average size of commercially exploited species within MPAs when compared to areas without fishing restrictions (Grandcourt et al. 2011b). Additionally, access restrictions around oil and gas platforms also result in de facto MPAs, as permits are required to approach within 5 km of these areas and where fishing prohibitions are strictly enforced. With several hundred of these restricted zones in place within UAE waters (>800), this consequently offers undeniable benefits to marine ecosystems within their borders and to the fishes that inhabit them (Bouwmeester et al. 2020). Finally, efforts are also being made to restore and conserve certain habitats. Under the guidance of UAE’s Ministry of Climate Change and Environment an extensive coral restoration project was announced in 2018 off the Fujairah coast. This project aims to build an artificial reef covering some 300,000 m³ which they suggest will help to protect and replenish fish population in the area, although care should be taken to ensure that this reef is placed within an MPA so as not to exacerbate overfishing on these highly concentrated fish communities (Feary et al. 2011).

7 Conclusion

The UAE is home to a diverse and abundant array of fishes that have contributed over several thousand years, and continue to do so, to the success of communities living in the UAE. Their value has always been associated with fisheries, providing a key source of nutrition, and supporting the second largest economic resource in the UAE. Yet our understanding of the true diversity of fishes in the UAE and their ecological value is vastly understudied. Recent studies have started to highlight how the extreme environments of the UAE alter fish physiology, behaviour and ecology, and have attracted attention from the global scientific community who are looking to the fishes of the UAE as a valuable model system for understanding how climate change will impact the worlds fishes. Hence, the fishes of the UAE represent a unique and internationally critical resource to research addressing the impacts of climate change and their conservation should be a priority at the national level.

8 Recommended Readings

Additional information on the overall ecology of the Arabian Gulf can be found in Vaughan et al. (2019) while Burt et al. (2011) and Feary et al. (2010) discuss how local fish communities fit into the broader regional picture and their value to understanding climate change impacts on fishes. Finally, Grandcourt (2012) provides a concise overview of coral reef fishes and fisheries in the Gulf.