Plate 8.1 Bottlenose dolphins (Tursiops sp.) escort the boat to harbor. 242 Marine Atlas of the Western Arabian Gulf

Transcription

1 Plate 8.1 Bottlenose dolphins (Tursiops sp.) escort the boat to harbor. 242 Marine Atlas of the Western Arabian Gulf

2 Amanda Hodgson Murdoch University, Western Australia Chapter 7: FISHERIES

3 Introduction Saudi Arabia s coastline represents a vital part of the habitat of at least three species of marine mammals found in the Arabian Gulf: Dugongs (Dugong dugon), bottlenose dolphins (Tursiops sp.) and Indo-Pacific humpback dolphins (Sousa chinensis). These three species are members of two different marine mammal orders: Sirenia (represented by the dugong) and Cetaceans (dolphins and whales). Other species of dolphins and possibly some whales likely utilize Saudi s Gulf waters, however, little is known about Saudi Arabia s marine mammal inhabitants. This chapter provides an overview of the documented records of dugong and dolphin sightings in Saudi Arabia s Gulf territory, what is known of the general biology and ecology of these animals, and the human activities that threaten their survival in these waters. The vulnerability of marine mammals There are a number of characteristics of marine mammals that make them particularly vulnerable to human impacts. Dugongs and dolphins have long life spans and are relatively late to reach a reproductive age compared to other animals. Females only give birth to one calf at a time after a gestation period of one year, and then invest a lot of time in caring for that calf, meaning it can be many years between each offspring. These life history characteristics result in slow rates of population growth and the population will only continue to grow if there is a high rate of survival within the adult population (at least 90% per year; Marsh, et al., 1984). The death or killing of even a few adults is likely to cause a decline in the population (Marsh, et al., 2002; Taylor, 2002). For dugongs this effect is multiplied when their habitat quality (i.e., available forage) is degraded and dugongs respond by reducing their breeding rates (Marsh and Kwan, 2008). Marine mammals tend to have extensive fat stores on their body to help maintain their body temperature. As a consequence of these fat stores, their long life spans, and for dolphins, their position high in their food chain, some species carry tissue pollutant levels that are among the highest recorded in all animals (Reijnders, et al., 1999a, b). Plate 8.2 Dugong (Dugong dugon) the legendary mermaids of Arabia are abundant in the shallow productive marine waters of the Gulf of Salwa. 244 Marine Atlas of the Western Arabian Gulf

4 The three resident marine mammals in Saudi Arabian Gulf inhabit inshore waters, the areas where humans also concentrate their activities. Coastal dolphins, such as bottlenose and humpback dolphins, are among the most threatened species of cetaceans in the world because of their close proximity to human activities (Thompson, et al., 2000; DeMaster, et al., 2001). Dugongs also rely on a food source, seagrass, which grows only in shallow inshore waters, and are threatened by coastal developments throughout most of their global range (Marsh, et al., 2002). Direct impacts of human coastal activity on marine mammals include death or injury from boat strikes, entanglement in fishing nets and hunting. Coastal activity also indirectly impacts marine mammals by reducing the quality of, or totally removing, their habitat. As a result of human population growth and the proportion of people throughout the globe living in the coastal zone, Marsh, et al., (2003) conclude that by the end of the 21st century, the number of extant populations and species of marine mammals will be fewer, and that the decline will be more pronounced for coastal species than non-coastal. Marine mammals as ecosystem sentinels Plate 8.3 Dugongs (Dugong Dugon) in Arabian Gulf. Dugongs and dolphins each utilize different parts of the marine ecosystem, but both feed at or near the top of the food chain. Dugongs are herbivores, eating mainly seagrass, and so form part of a relatively short food chain. In contrast, dolphins are top predators of a wide variety of fish and squid. As discussed in the previous section, marine mammals can accumulate high levels of toxins within their body, which makes these animals excellent sentinel organisms: species that indicate the health of the environment (Reddy, et al., 2001; Bossart, 2006). Marine mammals can indicate changes in the ecosystem through: a. Changes in their distribution, which may coincide with changes to their environment or in their prey distribution. b. Levels of pollutants in their tissue. c. Changes in their diet or body condition which may reflect changes to food webs (Moore, 2008). Chapter 8: MARINE MAMMALS 245

5 In the Arabian Gulf, marine mammals and their food sources may be particularly sensitive to human impacts on their habitat. The Gulf is a harsh environment. Although the geographical location is subtropical, the surrounding large, hot, arid continental landmass makes summers hotter and winters cooler than might normally be the case at this latitude. Large areas of Gulf waters experience periods of high temperatures, which lead to high evaporation rates and consequently high salinity levels. The Gulf s narrow entrance at the Straits of Hormuz, between Iran and Oman, restricts water flow and exchange, resulting in the persistence of high salinity levels (Sheppard, 1993). Only biota that can cope with high temperature ranges (from 11.4 C to 36.2 C) and salinity extremes can exist in some parts of the Gulf. An example is the Gulf of Salwa where barrier reefs to the north of Bahrain cause excessively low flushing rates (Sheppard, 1993). Some species are living at their tolerance limits and these species are particularly susceptible to additional stresses imposed by human activities (Sheppard, 1993). Monitoring of marine mammals can produce evidence of any additional stresses from human activities. There have been at least four die-offs of marine mammals in the Gulf since the 1980s. Two were due to oil spills during wars in 1983 and 1991 (Preen 1989, 1991). The other two in 1986 and 1991 resulted in 415 and 71 carcasses along the east Qatar and Saudi Arabian coastlines (Preen, 2004) and were thought to have been caused by morbillivirus (Tony Preen, personal communication). This virus, similar to measles in humans, affects dolphins worldwide. It is suggested that dolphins become less resistant to this disease when they have high levels of organochlorine contaminants (an industrial pollutant) built up in their system (Van Bressem, et al., 2001). Marine mammals are also effective sentinel species because they are charismatic and have great public appeal (Reddy, et al., 2001; Bossart, 2006). People s sentimentality about marine mammals makes them more likely to respond to deteriorating ecosystem health if this is reflected by disappearing marine mammal populations or sick animals washing up on coastal beaches. Their role as sentinels makes monitoring of marine mammal populations, and a detailed understanding of their ecological needs, a critical part of safeguarding the health of Saudi Arabia s environment. Plate 8.4 Bottlenose dolphins (Tursiops sp.). 246 Marine Atlas of the Western Arabian Gulf

6 Plate 8.5 Large herd of dugongs (Dugong dugon) in Gulf of Salwa.. What is Known About Marine Mammals in Saudi Arabia? Overview Marine mammals are ecologically important species which shape their environment and local food web. Little is known about the marine mammals of the Arabian Gulf apart from data obtained during the Saudi Arabian Government s Dugong Project (Preen, 1989). The project was initiated in 1985 in response to the Nowruz oil spill in The spill caused the death of at least 37 dugongs and 22 dolphins found along the Saudi Arabian coastline. Because the Gulf population of dugongs was thought to number only around 50 animals at the time, there were extensive fears for the further survival of the population (Preen, 1989). The Dugong Project was the first strategic attempt in the Gulf to identify and map dugong distribution and habitat, and estimate population size in the region. The goal was to develop a dugong management plan for the conservation of dugongs in the Gulf (Preen, 1989). The Dugong Project revealed that the Southern and Western Gulf is the world s second most important habitat for dugongs (Marsh, et al., 2002) and the most significant dugong habitat in the western half of its range (Preen, 2004). This area extends from Ras Tanura in Saudi Arabia to Abu Dhabi in the United Arab Emirates, including the coasts of Bahrain and Qatar, and an important area of Saudi Arabia s coastline at Khawr Duwayhin and Ghaghah Island. As a result of the Dugong Project, there are published sighting records of three species of cetaceans within Saudi Arabian Gulf waters: bottlenose dolphins, Indo-Pacific humpback dolphins and finless porpoises (Neophocaena phocaenoides), though the latter is thought to be an uncommon resident (Preen 1989, 2004). Other species noted to occur according to Saudi Arabia s National Biodiversity Strategy Action Plan (NBSAP) (NCWCD 2005) are the rough-toothed dolphin (Steno bredanensis), common dolphin (Delphinus delphis), striped dolphin (Stenella coeruleoalba), Risso s dolphin (Grampus griseus), spotted dolphin (Stenella attenuata), and finless porpoise. However, the NBSAP does cite references for this list of species and does not specify whether they occur in the Red Sea or the Gulf. The NBSAP also suggests there are 10 species of larger whales, but does not list these. Lindén et al., (2004) list the larger whales that occur in the Arabian Gulf as comprising: Bryde s whale, the humpback, minke, fin, and blue whales sperm, killer, and false killer whales. The author does not specify where in the Gulf these species can be found. Species considered common in or near the Jubail Marine Wildlife Sanctuary include common, bottlenose and humpback dolphins, while finless porpoises and Bryde s whale are considered rare (Robineau and Fiquet, 1996). Chapter 8: MARINE MAMMALS 247

7 Marine mammal aerial surveys Dugongs are difficult to see from a boat, they spend a short amount of time at the water surface, only coming to the surface briefly to breathe and showing very little of their body above the water. The most efficient way to record numbers and locations of dugongs, which tend to be dispersed over a large area, is to conduct aerial surveys. Flying at a low altitude, observers onboard an aircraft can see dugongs at the surface, as well as some dugongs that are beneath the water surface (depending on water clarity). Preen (1989, 2004) conducted aerial surveys of the Southwestern Arabian Gulf in winter (January to March) and summer (August to October) 1986, which included the Saudi Arabian coastline. The surveys were designed to record dugong distribution and abundance. However, the observers also record other marine fauna, including dolphins. The dolphin sightings were opportunistic, and the species could not always be identified. The summer survey did not include the northern coastal waters of Saudi Arabia because no dugongs were seen in that area during the first survey or during additional overflights and beach surveys (Preen, 2004). Dugong abundance and distribution During the winter survey of the Gulf of Salwa and the northern Saudi Arabian coastline, dugongs were only sighted in the area between Bahrain and Qatar. Most were within the largest herd of dugongs ever recorded in the world: 674 dugongs (Preen, 2004). The proportion of calves within this herd was approximately 16% (Preen, 2004). Because the dugongs were clumped within this one herd, a population estimate could not be calculated from this winter survey. During summer the dugongs were much more widely spread throughout the Gulf of Salwa and along the U.A.E. coastline. The population estimate calculated for the entire summer survey area was 5,840 (± 903 se) (Preen, 2004). The proportion of calves sighted during summer was 14.5%. Preen divided this survey area up into 10 blocks and the three blocks incorporated Saudi Arabian territorial waters. The population estimate for each of these blocks was: Block dugongs ± 258 se Block dugongs ± 159 se Block dugongs ± 197 se Dolphin abundance and distribution Dolphins were seen throughout the survey area during both surveys. A total of 404 dolphins were seen in winter and 516 in summer. Most of those identified to species within Saudi Arabian waters were bottlenose and humpback dolphins. Three sightings of finless porpoise (Neophocaena phocaenoides) were also seen during the winter survey in northern Saudi Arabian waters. A population estimate cannot be derived for each dolphin species because: (a) not all dolphins could be identified to species level, and (b) there are no data to determine corrections for dolphins not seen. Preen (2004) conducted a repeat aerial survey of U.A.E. waters in This showed that dolphin numbers (including both bottlenose and humpback dolphins) had dropped in this region by 71% since the 1986 survey. No repeat survey has been conducted for dolphins in Saudi Arabian waters to determine if a similar decline has occurred there. Plate 8.6 Dugongs have two nostrils near the top of their heads on a "fleshy lip," which can curl up to make breathing easier on the surface. 248 Marine Atlas of the Western Arabian Gulf

8 Plate 8.7 Dugongs (Dugong dugon) in Gulf of Salwa. Survey and analysis methods Survey and Analysis Methods Used in the Gulf Waters of Saudi Arabia used in the Gulf waters of Saudi Arabia Flight details The surveys by Preen were conducted in a helicopter, with a pilot, a flight coordinator and two observers on board (Preen, 2004). The survey flights followed transect lines spaced 2 nm (3.7 km) apart. The helicopter was flown at an altitude of m (500 ft) and speed of knots ( km/hr). The observers recorded animal sightings within a 195 meter wide strip either side of the transect line marked out by equipment attached to the outside of the helicopter. This meant the survey covered (sampled) 10%-12% of the total survey area. Analysis to determine dugong population estimate Plate 8.8 Female dugongs deliver one calf after a 12 month pregnancy, and the mother assists her new calf to reach the surface in order to take its first breath. To calculate a dugong population estimate for the entire survey area from the dugongs seen in the sampled area, corrections were made for: (a) dugongs not counted because they were too deep in the water to be visible when the aircraft passed over them (availability correction), (b) dugongs at the surface but not seen by the observers (perception correction), and (c) dugongs that were not within the 10%-12% of area sampled within the survey area. The availability correction is dependent on water clarity and depth. It was calculated by comparing the proportion of dugongs classified as at the surface when sighted during this survey, to the known total proportion of dugongs at the surface in Moreton Bay, Australia, where the water is clear and shallow enough to see all dugongs throughout the water column (Marsh and Sinclair, 1989). This method assumes that the proportion of dugongs at the surface at any one time is independent of water depth, temperature and dugong behavior. The perception correction was calculated by having the flight coordinator act as an observer wherever possible. His sightings could then be compared to the observer seated immediately behind him. For these periods, each sighting was categorized as being recorded by the observer, flight coordinator or both. These categories were then modeled (using a mark recapture framework) to calculate the probability of a dugong group being seen (captured) by the observer (Marsh and Sinclair, 1989). The Ratio Method (Caughley and Grigg, 1981; Marsh and Sinclair, 1989) was used to calculate the population estimate in each survey block and the associated standard errors. Each sighting was corrected for availability and perception and the mean group size per block before calculating the population estimate. Standard errors were estimated by accounting for these correction factors also. Chapter 8: MARINE MAMMALS 249

9 Biology and Global Status of Saudi Arabia s Marine Mammals The aerial survey conducted in 1986 is the only research conducted to date on marine mammals in Saudi Arabian Gulf waters. Detailed and long-term research on these marine mammals in other parts of the world has shown that behavior and some life history characteristics can vary from population to population and from habitat to habitat. This section gives a brief description of the three species of marine mammal considered resident within Saudi Arabian waters. It is stressed that local research on marine mammals is needed to determine whether populations in the Saudi Arabia and the Arabian Gulf region show the same traits and behaviors as those found elsewhere. Dugongs Status Plate 8.9 Dugong (Dugong dugon) preparing to dive. The dugong is a unique animal, being the only living species within its Family, Dugongidae, in the Order Sirenia. The only other species of Dugongidae was the large Steller s sea cow (Hydrodamalis gigas), from North Pacific waters. The Steller s sea cow was hunted to extinction only 27 years after its discovery in 1741 (Stejneger, 1887). Sirenians also include three species of manatees (Family: Trichechidae), which occur in the Caribbean Sea, the Amazonian Basin and West Africa. All species of manatee rely on freshwater (Reynolds and Odell, 1991), meaning that dugongs are the only truly marine mammal that is herbivorous (feeding only on seagrass). The dugong is listed by the World Conservation Union (IUCN) as vulnerable to extinction at a global scale (IUCN, 2009). The geographic range of dugongs includes suitable habitat from Mozambique, around the rim of the Indian Ocean, to Vanuatu in the Southwest Pacific (Nishiwaki, et al., 1981), including 37 countries and territories (Marsh, et al., 2002). The only quantitative population estimates have been obtained from Australia, the Eastern Red Sea and Arabian Gulf (Marsh, et al., 2002). Though dugong populations still exist at the historical limits of the animal s global range, it is believed most are relict populations now separated by large distances (Marsh, et al., 2002). Description When at the water surface, the lack of a dorsal fin is the easiest way to identify a dugong. They have thick brown skin, which becomes scarred as the animals age, and a tail shaped similar to a dolphin. Their eyes are small, and their paired nostrils are situated at the end of their snout. The dugong s head is distinctively shaped, with their muzzle directed downward and a modified upper lip that forms a rostral disc, which is covered with short bristles. The dugongs use this upper lip to grasp plant material, including rhizomes, and move the food into their mouth (Nishiwaki and Marsh, 1985; Preen, 1989). Their flippers are short and rounded at the ends and their mammary glands are located under the armpit of each flipper. Their skeleton is of very dense bone that acts as a weight to counteract the buoyant effect of the animal s fat reserves and help it sink in salt water to feed on seagrass beds (Nishiwaki and Marsh, 1985). Adults can reach over three meters in length and weight up to half a ton. Habitat requirements The dugong lives in tropical and subtropical shallow, sheltered coastal and island waters. They are restricted to warm waters of at least 15 C-19 C (Anderson, 1986; Hodgson, 2004) as a result of their low metabolic rate. Dugongs rely on seagrass beds for almost their entire diet, which they graze and uproot: this gives the dugong its popular name of sea cow. Although dugongs spend most of their time at water depths of less than 3 m (Chilvers, et al., 2004), they have also been reported 58 km from the coast where water depth was 37 m (Marsh and Saalfeld, 1989), and feeding trails have been recorded at depths of 33 m (Lee Long and Coles, 1997). There are three main species of seagrass in Saudi Arabian waters, Halophila ovalis, Halophila stipulacea and Halodule uninervis, and dugongs likely forage on all three species. Preen (1989) suggested that a possible limitation for dugong foraging in the Gulf is sediment type. He noted that all three seagrass species occur in sediments ranging from coarse sand to fine silt. However, dugongs were mostly sighted in waters deeper than 5-6 m where there is fine lose sediment rather than the coarse, compacted sediment found in shallower waters. The dugongs rooting mechanism, where the whole plant including the rhizomes is removed, is probably facilitated by the sediments found in the deeper waters. Therefore, dugongs preferred habitat in the Gulf may be waters of 6-10 m (where light conditions are suitable for seagrass growth), particularly in winter when seagrass die-back occurs and dugongs are dependent of getting at accessible rhizomes (Preen, 1989). Winter sea temperatures are another factor preventing dugongs from occurring in the northern Arabian Gulf. Waters north of Ras Tanura appear to be too cold for dugongs to regularly access the seagrass in that area (Preen, 2004). In winter the dugongs may regularly aggregate in the area between Bahrain and Qatar where the large dugong herd was seen during Preen s (2004) survey. Plate 8.10 The Dugong (Dugong dugon) is the last strictly marine herbivorous mammal remaining on the planet. 250 Marine Atlas of the Western Arabian Gulf

10 Plate 8.11 The Southern and Western Arabian Gulf is one of the world s most important habitats for dugongs, with the largest herds ever observed occurring in the Gulf of Salwa. More research is needed to determine the cause of this, but Preen suggests that as water temperatures drop during winter the dugongs may be aggregating around freshwater springs known to occur in the area. High salinity does not seem to substantially limit dugong distribution as they inhabit the southern end of the Gulf of Salwa, where salinity reaches 70. Of the whole area surveyed throughout the Gulf, there were two areas considered critical dugong habitat in Saudi Arabian territory (Preen, et al., 1989): 1. Coastline between Qatar and the U.A.E. 2. Waters between Saudi Arabia and Bahrain, bounded in the north by the King Fahd Causeway and in the south by Dwhat Zalum in Saudi Arabia and Ras al Barr in Bahrain. Life history Dugongs are long-lived with the maximum age estimated from growth layers in their tusks being 73 years (Marsh 1980, 1995, 1999). They are slow to reach sexual maturity with females having their first calf at 6 to 17 years of age, and bear a single calf every 3 to 7 years (Marsh, 1995; Kwan, 2002). Lactation lasts for at least 18 months (Marsh, et al., 1984). In several regions, calving is thought to be seasonal and the timing may ensure that birth corresponds with warm seasonal waters, avoiding temperature stress in the kg newborns (Marsh, et al., 1984). Preen (1989) notes that in the Arabian region, seagrass grows in summer, and that dugong calving is diffusely seasonal to correspond with this growth, meaning the newborns and mothers have access to the most nutritional forage. Behavioral ecology Dugongs can be found as a solitary animal or in herds of up to several hundred animals. The only place where dugongs are known to form large herds all year round is in Moreton Bay, in Queensland, Australia (Preen, 1995). These herds do not appear to have a strong social structure (Hodgson, 2004) with the strongest social bond being between a mother and her calf (Nishiwaki and Marsh, 1985). The largest, densest dugong herds tend to be feeding rather than conducting any other behavior (Hodgson, 2004). The dugongs cultivate the seagrass beds by removing 95% of the seagrass as they pass through a meadow and encouraging new growth of their favored (pioneer) seagrass species, which has the highest nutritional content (Preen, 1995). The home range of individual dugongs varies from 0.5 to 733 km² (Sheppard, et al., 2006). Dugongs have to move in response to tidal movements in places where they are dependent on seagrass growing in intertidal and shallow subtidal areas (Heinsohn, et al., 1977; Anderson and Birtles, 1978; Marsh and Rathbun, 1990). In places were dugongs are living at the higher latitudinal limits to their range, they use deeper waters as a thermal refuge from cooler inshore waters during winter (Anderson, 1986; Preen, 1992). Dugongs make similar winter movements in the Arabian Gulf. Dugong with large home ranges make long journeys in relatively short timeframes: one dugong traveled 560 km in just under 17 days (Sheppard, et al., 2006); another migrated between areas that were over 140 km apart three times in less than seven weeks (Marsh and Rathbun, 1990). Reports of dugongs appearing at Aldabra Atoll between the Seychelles and the Comoros Islands in the open Indian Ocean in 2001, mean these animals had crossed an ocean trench that is up to 4 km deep (Marsh, et al., 2002). Large numbers of dugongs have been known to move in response to changes in seagrass quality. Dugongs respond to mass seagrass loss by either remaining in the area and surviving on minimal forage (risking starvation), or moving to find seagrass elsewhere (Preen and Marsh, 1995; Gales, et al., 2004; Marsh, et al., 2004). Chapter 8: MARINE MAMMALS 251

11 Bottlenose Dolphins Status Bottlenose dolphins are part of the family Delphinidae and genetic studies currently suggest at least two species exist: the Indo-Pacific bottlenose dolphin Tursiops aduncus and the common bottlenose dolphin Tursiops truncatus (Rice, 1998; Leduc, et al., 1999; Natoli, et al., 2004). Indo-Pacific bottlenose dolphins occur in temperate to tropical waters from South Africa in the west, along the rim of the Indian Ocean to the southern half of Japan and southeast Australia (Hammond, et al., 2008a). Common bottlenose dolphins are distributed in tropical and temperate waters worldwide (Hammond, et al., 2008b). In the Arabian region, the dolphins previously reported as T. truncatus are now thought to be T. aduncus (Wells and Scott, 2002) although both species possibly occur in the Gulf and within Saudi Arabian waters (Hammond, et al., 2008a, 2008b). The IUCN classifies common bottlenose dolphins as of least concern and Indo-Pacific bottlenose dolphins as data deficient; both population trends unknown (Hammond, et al., 2008a, 2008b). Description Bottlenose dolphins are medium sized animals, ranging from 2 m to 3.8 m in length for adults, with evidence that body size tends to be larger in colder regions (Wells and Scott, 2002). Their robust body is dark grey on top with a lighter colored belly and in some areas they have a light streak along their side (Wells and Scott, 2002). The dorsal fin is taller and more curved than that of the Indo-Pacfic humpback dolphin. Life history Almost nothing is known of the ecology of coastal dolphins in the Arabian region (Baldwin, et al., 2004). Elsewhere bottlenose dolphins have a lifespan of up to 50 years and start reproducing at 5 to 14 years (Mann, et al., 2000; Wells and Scott, 2002). Calves are born mostly in summer after a 12 month gestation period (Wells, et al., 1987; Connor, et al., 1996; Mann, et al., 2000). Calves start learning to catch fish from 4-6 months of age, but continue to suckle for the first 3 to 6 years of life (Wells, et al., 1987; Mann and Smuts, 1998; Mann, et al., 2000). Females can give birth the season immediately following weaning of a calf as they can be pregnant and lactate (produce milk) simultaneously (Mann, et al., 2000). Mating and calving of bottlenose dolphins in the Arabian Gulf appears to occur from April to November (Baldwin, et al., 1999). Habitat requirements According to Preen s (2004) survey, bottlenose dolphins in the Gulf occur equally in shallow and deep waters, embayments and open waters. This species is common in the lower Gulf of Salwa, where salinity is (Preen, 2004). In other parts of their range, the habitat use of bottlenose dolphins varies. Some populations migrate seasonally, however, many populations remain in one habitat area year-round, and individuals have been recorded within stable home-ranges for many years (Wells and Scott, 2002). This species prey and foraging strategies also vary between populations. In general bottlenose dolphins feed on a variety of fish and squid species found associated with reef, sandy bottom, inshore and seagrass habitats (Wells and Scott, 2002). The tactics used for capturing these prey items can vary between individuals within a single bay and these tactics are thought to be passed from mother to offspring (Mann and Sargeant, 2003). In some populations these dolphins cooperate to herd schools of fish for feeding on (Wells and Scott, 2002). Behavioral ecology Plate 8.12 Bottlenose dolphins in Saudi Arabia. Different populations of bottlenose dolphins exhibit various types of social organization. Nothing is known of their social behavior in the Gulf, however, from studies elsewhere they are known to have complex societies with a high degree of social structure (Connor, et al., 1992, 2000; Mann, et al., 2000). Bottlenose dolphin groups are mostly unstable where membership changes regularly and multiple groups constantly join and split; described as a fission-fusion society (Wells, et al., 1987; Smolker, et al., 1992). Female groups are typically larger than males (Scott, et al., 1990), although the size of groups can depend on the preference of individuals (Mann, et al., 2000). In some populations in Australia and the U.S., male bottlenose dolphins form coalitions where pairs of males have long-term alliances and team up with other pairs to form super-alliances when they are herding and competing for females (Connor, et al., 1992, 2000). Case studies from different geographical locations indicate that there is a wide range of factors influencing or aiding bottlenose dolphin movement. Dolphins in California were observed in the 1980s to travel 500 km northwards in response to an El Nińo warm water event (Wells and Scott, 1999), and a single satellite tracked dolphin in Japanese waters travelled 604 km in 18 days with the Kuroshio Current (Tanaka, 1987). Indo-Pacific Humpback Dolphins Status Indo-Pacific humpback dolphins also belong to the family Delphinidae. The taxonomy of Sousa in the Arabian Gulf remains unclear as this population more closely resembles Sousa plumbea than Sousa chinensis, particularly in its highly conspicuous dorsal hump (Baldwin, et al., 2004). However, pending further morphological and genetic studies, humpback dolphins in the Gulf continue to be considered S. chinensis. (Rosenbaum, et al., 2002; Baldwin, et al., 2004). Humpback dolphins are considered near threatened by the IUCN (Reeves, et al., 2008). The species is known, or thought to have, declined throughout most of its range, and is likely to become threatened in the near future (Reeves, et al., 2008). More genetic studies are needed throughout its range, including the Arabian Gulf region, to determine the biodiversity and conservation status of this species. There are no data to determine whether the population is declining in the Gulf. Anecdotal reports from fishermen suggest that the species has declined in the past few decades, possibly a result of coastal development (Baldwin, et al., 1999). Description Humpback dolphins in the Arabian Gulf are only slightly lighter in color than bottlenose dolphins. In part of their range, including the Arabian Gulf the dolphins develop spotting over their head and back as they age (Ross, 2002). Their most distinguishing feature is their pronounced ridge or hump below their relatively short dorsal fin. They also have shorter more rounded pectoral (side) fins than bottlenose dolphins, and a longer narrower beak (Jefferson and Karzemarski, 2001). Throughout most of their range they grow to meters, but the largest dolphin measured in Oman was 3.14 m (Baldwin, et al., 2004). In South Africa, the species is sexually dimorphic with males growing slightly larger than females and this may also be the case in the Arabian Gulf (Ross, 2002). Life history Much less is known of the life history of humpback dolphins. It is suggested that they live for up to 40 years (Parra, et al., 2004), and mature at 3 to 10 years (Ross, 2002). The calving interval is thought to be 3 years (Karczmarski, 1999), and gestation is approximately 10 to 12 months (Jefferson and Karzemarski, 2001). Habitat requirements Indo-Pacific humpback dolphins generally occur in waters less than 15 m deep and within 10 km of the coast, which is likely related to the high productivity associated with mangrove and estuarine areas (Karczmarski, et al., 2000; Jefferson and Karzemarski, 2001; Keith, at al., 2002; Parra, et al., 2006b). The distribution of humpback dolphins with the Gulf reinforces the importance of nearshore habitats for this species. In Oman, humpback dolphins are one of the most commonly observed species from the shoreline, while boat based surveys, which do not focus on nearshore areas, have low humpback dolphin encounter rates (Baldwin, et al., 2004). Preen (2004) recorded 96% of humpbacked dolphin sightings within the 10 meter isobath. Specifically, humpback dolphins in the Gulf appear to prefer coastal waters with soft sediments and a low energy, sandy shoreline (Baldwin, et al., 2004). They have been observed using a unique feeding strategy in these areas, herding fish onto exposed sand banks and deliberately beaching themselves in order to capture their prey (Baldwin, et al., 2004). It is suggested that in Oman, humpback dolphins feed on sciaenid fishes and their diet includes a relatively high amount of cephalopods and crustaceans, although detailed analyses of stomach samples is still needed (Baldwin, et al., 2004). Behavioral ecology In other populations of humpback dolphins, individuals do not permanently reside in particular bays or habitat areas, but rather show patterns of emigration and immigration, spending periods of months in each area (Parra, 2006). Mating behavior and the presence of calves occurs from April to December in the Arabian Gulf (Baldwin, et al., 1999, 2004). The social behavior of humpback dolphins is largely unknown, however, in the Arabian Gulf this species occurs in unusually large groups of up to 100 animals. Elsewhere, groups tend to be smaller, which may reflect a unique social behavior in the Arabian Gulf region (Baldwin, et al., 1999, 2004). Around Oman, humpback dolphins occasionally associate with other dolphin species, such as bottlenose dolphins and the longbeaked common dolphin (Delphinus capensis tropicalis) (Baldwin, et al., 2004). 252 Marine Atlas of the Western Arabian Gulf Chapter 8: MARINE MAMMALS 253

12 Conservation Patterns of human activity have changed extensively throughout the Arabian Gulf in recent decades (Price, et al., 1993; Abuzinada, et al., 2008). Rapid development activities have made a great impact on the coastal zone and its shallow waters. Saudi Arabia s National Strategy for Conservation of Biodiversity (NCWCD, 2005) seeks to address a range of threats to marine mammals in the Arabian region, including incidental capture in fishing nets, overfishing, agricultural activities, dredging and land reclamation and pollution. The proposed strategy is to: promote the conservation of biodiversity and the sustainable use of resources by placing biodiversity at the core of national planning and development. This is a complex undertaking, as the effects and ramifications of multiple individual threats can add together to create cumulative threats. Habitat loss and degradation As herbivores feeding almost exclusively on seagrass, dugongs rely on a food source that is very sensitive to human impact (Marsh, et al., 1999). Typically the areas that provide the ideal water conditions and shelter for seagrass growth are also the ideal sites for port development and/or are downstream from heavily disturbed catchments and as a result, degradation of their habitat has occurred throughout much of the dugongs range (Marsh, et al., 2002). Sedimentation can occur naturally, particularly as a result of cyclones and extreme rainfall events, but has been enhanced by human activities, such as clearing of inland and coastal vegetation, which has increased erosion (Green and Short, 2003), and dredging and land reclamation (Erftemeijer and Lewis, 2006). The stress caused by these human impacts then affects the ability of the seagrass to recover from natural events, such as flooding and storms (Wachenfeld, et al., 1998). By 1990, 40% of the coastline of Saudi Arabia had been reclaimed or greatly impacted by adjacent landfill or oil contamination (Sheppard et al., 1992). Land reclamation is one of the most destructive activities to coastal and marine ecosystems, causing severe and permanent destruction of habitat through burial and direct obliteration. Dredging destroys seagrass in the dredged area and the resulting increase in sedimentation is known to cause long-term smothering and destruction of seagrass beds (Price, et al., 1983). The physical scouring caused by dredging can make seagrass growth impossible for many years. The level of seagrass destruction caused by dredging and land reclamation in Saudi Arabia is unknown as there are no historical records of seagrass habitat and water turbidity levels with which to compare current conditions. The small colonizing seagrass species found in Saudi waters tend to recolonize relatively quickly following an impact, but do not endure long once environmental conditions are beyond that to which they can adapt (Erftemeijer and Lewis, 2006). Land reclamation can also change ocean current patterns and water movements (Al-Madany, et al., 1991; Erftemeijer and Lewis, 2006), and the changed wave action can have detrimental effects of seagrass beds. The effect of habitat loss on dugongs was exemplified in Hervey Bay, Australia. Widespread loss of seagrass beds during a cyclone resulted in the death and emigration of many dugongs from this important habitat area (Preen and Marsh, 1995). When their access to forage is limited, dugongs also respond by delaying breeding, which can significantly reduce population growth (Marsh and Kwan, 2008). The destruction of intertidal areas through land reclamation also is likely the most significant impact affecting dolphin populations. The humpback dolphins preferred nearshore areas of high productivity typically associated with mangroves and estuaries (Parra, 2006) were still being destroyed along the Saudi Arabian coastline in the early 1990s (Sheppard et al, 1992). The resultant loss of nutrient flow, together with the loss of fish nursery habitat through the destruction of seagrass beds, has likely reduced the fish stocks, and therefore, the areas of suitable habitat available to both dolphin species. Plate 8.13 Bottlenose dolphins (Tursiops sp.) in the Gulf of Salwa. Both bottlenose and humpback dolphins show a high level of site fidelity, consistently returning to particular habitats to forage and socialize (Parra, 2006). Species with high levels of site fidelity and restricted nearshore habitats are particularly vulnerable to population declines as a result of habitat degradation and loss (Warkentin and Hernandez, 1996). The various habitats within the home ranges of individual dolphins are unlikely to be of the same quality, and the distance between good quality habitat increases with continued degradation of coastal habitats, causing habitat fragmentation (Andrén, 1994). Dolphins that once regularly used the modified area can no longer find suitable food and will then have a lower chance of survival. Bottlenose dolphins can co-exist with coastal development (e.g., Chilvers, et al., 2005), however there are many studies providing evidence that this species exhibits subtle changes in their behavior in response to human impacts that can negatively impact and endanger local populations (e.g., Bejder, et al., 2006b). With our limited knowledge of the habitat requirements of these coastal dolphin species, their conservation can only be assured by adopting the precautionary approach of preserving the quality of their core habitat areas. Therefore, efforts to determine what areas within Saudi Arabian waters represent a key habitat for bottlenose and humpback dolphins, and to maintain or improve the habitat quality inside and adjacent to these key areas will play a key role in the persistence of local populations in Saudi Arabia. 254 Marine Atlas of the Western Arabian Gulf

13 Plate 8.14 Bottlenose dolphins live in groups, typically with between 10 to 30 members. These groups are known as pods. Pollution The principle sources of chemical pollutants and toxins in Saudi Arabia include oil that has spilled from oil tanker or oil facility accidents, ballast water from vessels containing oil and chemicals, pollution from industrial sources, and runoff from residential and agricultural areas, and discharge from wastewater treatment facilities (NCWCD, 2005). Environmental pollutants threaten marine mammals both directly, through accumulation of toxins in the body, and indirectly, by polluting their habitat (Reijnders, et al., 1999b). For example, some dugongs in Queensland, Australia, were found to have high levels of dioxins, which are attached to the sediment they ingest when uprooting their seagrass forage (Haynes, et al., 1999; McLachlan, et al., 2001). Dugongs can also accumulate high levels of heavy metals as they age, but the effects of this are unknown (Haynes, et al., 2005). Diuron, a component of herbicides, can reduce seagrass growth even when in low concentrations (Haynes 2001). Dolphins are particularly susceptible to persistent organic pollutants (POPs) because of their position high up in the food chain, meaning that the pollutants build up in their fish prey and then accumulate within their body fat throughout their life (Reijnders, et al., 1999b; Pierce, et al., 2008). The effects of these pollutants include depression of the immune system, increased risk of infection and disease, reproductive failure and the impairment of offspring (Reijnders, et al., 1999b; Pierce, et al., 2008). Pathogen pollution may also have considerable negative effects on populations of coastal marine mammals (Kreuder, et al., 2003). Humpback dolphins are known to be susceptible to Toxoplasmosis gondii (Bowater, et al., 2003), a terrestrial parasite that can be fatal or negatively affect the health of marine mammals. This parasite is probably transferred to the coastal ecosystem via runoff of contaminated water with cat faeces or litter (Miller, et al., 2002). Therefore, controls on the disposal of cat faeces, and improvements of the treatment of stormwater and sewage discharges is fundamental to prevent the pathogen infection. The amount of discharge into the marine environment from desalinization plants throughout the Gulf is equivalent to the flow of a major river and Saudi Arabia is the second biggest source of this pollutant (Lattemann and Höpner, 2008). The discharge is highly saline, has elevated temperatures and reduced oxygen content, and contains chemical pollutants including chlorine, antiscalants and heavy metals. Shallow coastal areas where seagrass occurs are vulnerable because they have low water exchange and sediment mobility so the pollutants are not flushed out of these ecosystems (Lattemann and Höpner, 2008). The Nowruz oil spill in 1983 led to the death of an estimated 60 dugongs and several times as many dolphins along the Saudi Arabian coast (Preen, 1989; Sadiq and McCain, 1993). A further 93 marine mammals died during the Gulf War in 1991, including 14 dugongs, 57 bottlenose dolphins, 13 humpback dolphins, one finless porpoise, and eight unidentified dolphins. The anti-clockwise circulation of Gulf waters carries spills along the Qatar, Bahraini and Saudi Arabian coasts, making these habitats particularly vulnerable to oil spills (Preen, 1989). Oil can harm dugongs or dolphins by covering nostrils, congesting or damaging the respiratory system, or inhaling droplets of oil or oil fumes (Krupp and Abuzinada, 2008). In dugongs it could also be ingested with seagrass or sediments or cause starvation due to seagrass death (Preen, 1989). The degradation of seagrass beds through oil pollution also affects dolphins by destroying their prey fish nursery habitat. However, if given the opportunity, dolphin populations can recover. One year after the Gulf War oil spill there was no evidence of increased deaths of dolphins within the proposed Jubail Marine Wildlife Sanctuary and a group of humpback dolphins had returned to a heavily polluted site (Robineau and Fiquet, 1994). Chapter 8: MARINE MAMMALS 255

14 Vessel strikes and disturbance Boats can interrupt dugongs feeding when they pass by dugong herds (Hodgson and Marsh, 2007). Although dugongs are more likely to respond to boats passing within 50 m, they have been observed responding to boats over 500 m away (Hodgson and Marsh, 2007). What determines dugongs detection distance and response to boats, and the effects of interrupting their feeding, have not been quantified (Hodgson and Marsh, 2007). Potential costs of disturbance include reduced energy intake, increased energy expenditure while fleeing from boats, and exclusion from preferred seagrass patches (Hodgson and Marsh, 2007). By effectively reducing dugong habitat quality disturbance from boats could cause emigration, reduced fecundity or even starvation in dugongs. Similarly, disruptions of the behavioral activities of dolphins leads to displacement from their preferred habitat and reduced fitness and fecundity, which can potentially result in population declines (Bejder, et al., 2006a, 2006c; Williams, et al., 2006; Stensland and Berggren, 2007). Boats can prevent dolphins from accessing particular areas within their home range (Allen and Read, 2000) and alter their behavior (Lusseau, 2003; Constantine, et al., 2004). Acoustic communication between humpback dolphins and their ability to maintain cohesive groups is also impaired by boat traffic and noise (Van Parijs and Corkeron, 2001). Boat strikes are a significant cause of dugong mortality in Australia (Greenland and Limpus, 2006), and can also cause serious injuries and mortalities to coastal dolphins (Wells and Scott, 1997; Parsons and Jefferson, 2000). The delayed response of dugongs to boats makes them particularly vulnerable to large and/or high speed vessels (Groom, et al., 2004; Hodgson, 2004). Shallow waters represent particularly high risk areas for dugongs as they cannot dive deep to avoid vessels (Hodgson, 2004) and in Australia they have been crushed between boats and the seabed (Yeates and Limpus, 2003). There are currently no dugong or dolphin mortality records for Saudi Arabia and therefore it is hard to assess the magnitude of this threat. However, it may be possible to minimize the risk of boat strikes to dugongs by defining critical dugong habitat as Go Slow Zones, or defining boating channels through deep waters and thereby directing boat traffic away from shallow high risk areas (Maitland, et al., 2006). However it is critical to maintain a high level of compliance with these regulations (Groom, 2003; Hodgson, 2004). Fishing activities Entanglements in fishing nets have long been recognized as a major threat for coastal dolphins (e.g., Cockcroft, 1990; Paterson, 1990; Hale, 1997). There have been reports of humpback dolphins being incidentally captured and drowned in fishing nets in the Gulf (Baldwin, et al., 1999). In Oman, dolphin carcasses have been found in the vicinity of fishing areas still entangled or with scarring evidence of entanglement (Baldwin, et al., 2004). Shrimp trawler boats operate Saudi Arabian waters (Abdulqadar, 2006) and may contribute to the degradation of dugong habitat areas. Bottom trailing is the most destructive fishing gear currently in use (Watson, et al., 2006). Trawling directly damages seagrass beds (Leriche, et al., 2006), degrades seagrass through increased turbidity (Preen, et al., 1995), and limits seagrass recovery by leaving sea beds unsuitable for recolonization (Tanner, 2003). Climate change In addition to natural stressors and human impacts, global warming threatens to add further pressure to these inshore marine mammals. Potential detrimental effects of global warming on seagrass beds include plant community changes, the decline or elimination of communities due to increases in water depth, changes to tidal regimes, salinity changes, increased UV radiation, increased turbidity and growth of epiphytes (Short and Neckles, 1999). Global warming has already bleached and killed coral communities in the Gulf (Anon, 2006). The effects of climate change on marine mammal habitats need to be considered in the context of the potential impacts of other human activities. When combined with other impacts, global warming presents a serious threat to marine mammals. Plate 8.15 Bottlenose dolphins socializing on the surface. 256 Marine Atlas of the Western Arabian Gulf

15 Plate 8.16 Dugongs are found in warm shallow waters of the Arabian Gulf where they feed exclusively on seagrass. Minimizing impacts on marine mammals through international cooperation Wild animals do not heed international borders, and so a regional approach to the management of human impacts on marine mammals is essential (Preen, et al., 1989). Dugongs proven capacity to undertake long distance journeys indicates that management should be coordinated internationally (Marsh, et al., 2002). The Gulf of Salwa, which is a hotspot for dugongs, exemplifies this geographical complexity: it is an embayment half comprised of Saudi Arabian Coast and half of Qatari Coast, and is almost closed off by the island of Bahrain. Saudi Arabia s commitment to conserve all species of wildlife within the Kingdom is demonstrated by ratifying the Convention on Biological Diversity and fulfilment of its obligation to prepare a National Biodiversity Strategy (NCWCD, 2005). Within their report to the convention on the Kingdom s protected areas, the NCWCD suggested that Saudi was in discussions with Bahrain and Qatar to establish a transboundary marine reserve in the Gulf of Salwa in recognition of the large dugong population residing there (NCWCD, 2003). This reserve has not yet been established. Saudi Arabia is also a signatory of the Convention on Migratory Species. Saudi Arabia is also a signatory of the Convention on Migratory Species, which specifically addresses the conservation of transboundary species. However, Saudi Arabia has not yet signed the Memorandum of Understanding on the Conservation and Management of Dugongs (Dugong dugon) and their Habitats throughout their Range, which recognizes that the conservation of dugongs and management of human impacts on this species requires the cooperation of the countries within their range. The MOU states that the signatories express their desire to work closely together to improve the conservation status of dugongs and the habitats on which they depend. All states within the dugongs range in the Arabian Gulf are also members of the Regional Organization for the Protection of the Marine Environment (ROPME), an organization which reflects the goodwill of these countries to cooperation in protecting their common marine environment. Through ROPME there is the potential to coordinate research of marine mammals and development regional protection policies. Chapter 8: MARINE MAMMALS 257

16 Research and management needs for the conservation of marine mammals in Saudi Arabia Preen, et al., (1989) provided the Saudi Arabian government with a comprehensive series of recommendations for the conservation of dugongs in the Arabian Region. A number of these recommendations have not been followed and to our knowledge there has been no research on marine mammals in Saudi Arabian waters since Preen s (2004) survey in The following outlines the research and management actions needed for the conservation of marine mammals in Saudi Arabia. 1. Defined objectives and management plan for marine mammal conservation The Saudi Arabian government needs to define the ecological and socio-economic objectives for marine mammal conservation and the management of human impacts on these animals in Saudi Arabian waters. It will be impossible to determine the effectiveness of management and research of marine mammals in Saudi Arabia without explicit objectives against which to assess the species conservation outcomes. Ultimately the management of human impacts on marine mammals needs to be coordinated at the scale of the Arabian Gulf as a whole. So, in addition, the Saudi Arabian government should work with Bahrain, Qatar and the U.A.E. to define the objectives for marine mammal conservation and management in the region. The government should then develop a management plan for the waters of Saudi Arabia in consultation with appropriate stakeholders. The plan should include a program of research and monitoring of threatened marine mammals to inform the agreed management objectives. This should be developed in conjunction with a management plan for the waters of the Arabian Gulf, which would provide overarching policy for the plans for individual countries. 3. Regular monitoring of marine mammal populations Regular surveys of dugong and dolphin populations provide standardized abundance estimates and therefore can indicate population trends within the survey area. Such surveys also provide information on marine mammal distribution, and therefore can indicate the relative importance of habitat areas, movements between these areas, and whether these areas change over time. Ultimately, the best information would be obtained by regularly surveying the entire Gulf region. For example, dugong surveys are conducted every five years in important habitat areas in Australia, providing long-term trends in dugong populations. 4. Research on behavior and movement patterns The two best methods to determine dugong movement patterns are: (1) regular aerial surveys, and (2) satellite tagging. Tracking dugongs using satellite tags has provided important information about dugong movements, habitat use and behavior in Australia (Sheppard, et al., 2006). Satellite tagging dugongs could potentially determine to what degree individual dugongs move across borders of the Gulf nations, and whether new land reclamation developments or other human activities have the potential to hinder dugong movement patterns. 7. Genetic research Recent genetic research using mitochondrial (maternally inherited) DNA shows regional differentiation between dugong populations along the coast of the state of Queensland, Australia (Blair, et al., in review). A similar study of dugong populations in Saudi Arabia and surrounding Gulf countries would enhance our knowledge of the interconnectedness between these populations and provide a baseline for determining the best spatial scale at which to manage dugongs in the Arabian Gulf. Genetic studies are also needed for both dolphin species as the taxonomic status of both is currently unclear. The bottlenose dolphins could be Tursiops aduncus or T. truncates, or possibly both species occur in Saudi Arabian waters (Hammond, et al., 2008a, 2008b). There is also debate as to whether the humpback dolphins in the Arabian Gulf are Sousa chinensis as their anatomical characteristics more closely resemble Sousa plumbea (Rosenbaum, et al., 2002; Baldwin, et al., 2004). Genetic work would help determine the biodiversity and conservation status of both species in the region as well as the population structure and relatedness of dolphins inhabiting the waters of Saudi Arabia and surrounding Arabian states. This information would provide a baseline for determining the best spatial scale at which to manage dolphins in the Arabian Gulf. 2. Updated status assessment of marine mammals in the Arabian Gulf Dugongs are known to conduct large scale movements in response to changes in seagrass availability (Kwan, 2002; Gales, et al., 2004; Sheppard, et al., 2006). Therefore an accurate comparison between the current status of the dugong population in Saudi Arabia and the 1986 estimate (Preen, 2004), requires a repeat of the entire aerial survey conducted in 1986 rather than a single territory. Even less is known about the status of dolphins in Saudi Arabia than is known about dugongs because the most accurate method to estimate populations of dolphin species is through boat based surveys (Parra, et al., 2006b), which have never been conducted in Saudi Arabian waters. Line transect boat based surveys throughout Saudi Arabian waters, or preferably, throughout the Southwestern Gulf, should be conducted as soon as possible to provide critical information about the status of both bottlenose and humpbacked dolphin populations, and the important habitats for these species. A repeat aerial survey for dugongs and a boat-based dolphin survey would provide an updated status assessment of marine mammals in the Arabian Gulf region. This contemporary data can be used to develop the management plan and outline the management actions needed to conserve this species. 5. Photographic identification surveys for dolphins Photographic identification surveys for dolphins provide information on abundance, site fidelity and residence patterns, and from this it is possible to identify the habitat areas critical for the conservation of each dolphin species (Parra, et al., 2006a). These surveys rely on taking photographs of the dolphins dorsal fins, which have unique shapes and scaring that are used to identify individuals. By calculating the encounter rates of new individuals per survey it is possible to estimate the abundance of dolphins within the survey area. The technique provides detailed information about local populations in defined areas. The surveys need to be conducted over a number of years (depending on the size of the population) to produce a rigorous population estimate, however, this technique provides the most accurate estimate of abundance along with insights into dolphin social structure through the analysis of group composition and from behavioral observations conducted during encounters. 6. Spatial models for each marine mammal species The data from previous and future aerial and boat based surveys should be incorporated into a spatially explicit density model for each marine mammal species (Grech and Marsh, 2007). These models can be used to prioritize areas for the conservation of marine mammals. They can also be used to produce a spatial risk assessment to determine the most threatening human impacts for marine mammals throughout the Arabian Gulf (Grech and Marsh, 2008). 8. Assessment of the major cause of mortality An assessment of the major cause of mortalities of marine mammals would provide an indication of the relative significance of threats caused by human activities to these animal populations. All vessel operators and users of the marine and coastal environment are a potential source of information if they are encouraged to report any deaths or injuries of marine mammals. In addition, it should be compulsory for fishers to report all by-catch of threatened species. There are various methods of encouraging the public to report strandings or mortalities such as a Marine Animal Hotline and/or website. The most appropriate method for Saudi Arabia should be determined through social research. A marine mammal mortality database should be established and administered by the government. The database records would provide information on mortality rates (and sustainability of human impacts) and species distribution. 9. Regular monitoring of seagrass A program that monitors seagrass distribution and health should be established in Saudi Arabia in collaboration with surrounding Gulf countries to assess the condition of these seagrass ecosystems. Seagrass monitoring can provide an early warning system for the health of nearshore habitats of dugongs and dolphins. 258 Marine Atlas of the Western Arabian Gulf

17 Plate 8.17 Dugongs (Dugong dugon) surfacing to breath between longer dive periods in which they feed on seagrass growing on the bottom of the Gulf. Plate 8.18 Bottlenose dolphins (Tursiops sp). Plate 8.19 Dugong (Dugong dugon). Chapter 8: MARINE MAMMALS 259

18 Map 8.1 Dolphin Observations - Northern Region.

19 Map 8.2 Dolphin Observations - Southern Region.

20 Map 8.3 Dugong Observations - Southern Region.

21 Map 8.4 Dugong Observations - Ras Abu Qamees.