BIODIVERSITY ANNUAL REPORT 2016 STATUS OF DOLPHINS IN ABU DHABI

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1 BIODIVERSITY ANNUAL REPORT 2016 STATUS OF DOLPHINS IN ABU DHABI

2 EXECUTIVE SUMMARY Dolphins are apex predators that bio-accumulate marine toxins, consequently, they are good indicators of marine environmental quality. As very little was known about the ecology and conservation status of dolphin species in Abu Dhabi waters, the Environment Agency Abu Dhabi started a dolphin survey in This aimed to determine baseline population size estimates, distribution and threats as a basis for monitoring and conservation management planning. Between 2014 and end of 2016, 64 days of vessel based surveys were completed covering 5,592 km of survey track. A total of 403 Indian Ocean humpback dolphins (Sousa plumbea), 693 Indo-Pacific bottlenose dolphins (Tursiops aduncus), and 52 finless porpoises (Neophocaena phocaenoides) were recorded. Using the photo-identification and mark-recapture technique, it was estimated that 701 Indian Ocean humpback dolphins and 1,834 Indo-Pacific bottlenose dolphins inhabit Abu Dhabi s waters. The Indian Ocean humpback dolphin population in Abu- Dhabi is the largest reported for this species in the world. A large proportion of dolphins (13% of the Indo-Pacific bottlenose dolphins and 12% of the Indian Ocean humpback dolphins) had cuts and scars on their dorsal fins and/or body which were derived from propeller strikes or entanglement in fishing gear. Other threats to Abu Dhabi s dolphins include habitat loss from dredging, land reclamation, port and harbour construction, noise pollution and other development activities which are concentrated in the shallow coastal waters and channels. PAGE 2

3 INTRODUCTION Perhaps because of their permanent smiles and playful nature, dolphins are amongst the most endearing species in the animal kingdom. In addition to being charming and charismatic marine mammals, they are apex predators that bio-accumulate marine toxins, playing an important role as indicators of marine environmental quality. Only two species of dolphin, the Indo-Pacific bottlenose dolphin (Tursiops aduncus) and the Indian Ocean humpback dolphin (Sousa plumbea) are common residents of Abu Dhabi s coastal waters. The Indo-Pacific bottlenose dolphin is listed as Data Deficient and the Indian Ocean humpback dolphin is proposed to be listed as Endangered on the IUCN Red List. Another small cetacean, the finless porpoise (Neophocaena phocaenoides) is seen very rarely and is listed as Vulnerable on the IUCN Red List. As there was very limited information on these species, the Marine Division of the Terrestrial and Marine Biodiversity Sector has been implementing a dolphin survey since 2014 in order to better understand their ecology and status. The survey aims to determine population sizes, distribution and threats to dolphins in Abu Dhabi s coastal waters in order to establish a monitoring baseline and support effective conservation management planning. PAGE 3

4 BIOLOGY OF DOLPHINS SPECIES FOUND IN ABU DHABI S COASTAL WATERS Indo-Pacific bottlenose dolphin (Tursiops aduncus) The Indo-Pacific bottlenose dolphin grows up to 2.6 m and weighs up to 230 kg. They feed on a wide variety of fish and cephalopods, particularly squid. This species is found in both the coastal and off-shore waters of Abu Dhabi where it can occur in groups of up to 45 individuals. The peak mating and calving seasons are in the spring and summer, although mating and calving occur throughout the year in some regions. Sexual maturation occurs at between years, gestation lasts 12 months and calves are born between 0.8 and 1.5 m long. Calves can remain with their mothers for up to six years and females typically only have a calf every three to six years over a life span of more than 40 years. PAGE 4

5 Indian Ocean humpback dolphin (Sousa plumbea) The Indian Ocean humpback dolphin grows up to 2.7 metres and weighs up to 260 kg. It is a slow swimming dolphin, typically travelling at an average speed of 4.8 km/hr. It feeds on a variety of fishes, cephalopods and crustaceans in waters less than 25 m deep and is rarely seen more than 3 km from the shore. It is found in shallow waters and channels around the off-shore islands and the mainland of Abu Dhabi where it occurs alone or in groups of up to 24 individuals. Sexual maturation occurs at 10 years for females and years for males, gestation lasts 12 months and the size at birth is 1 m. Calves can remain with their mothers for up to four years and females typically only have a calf every three years over a life span of at least 40 years. PAGE 5

6 DOLPHIN SURVEYS IN ABU DHABI COASTAL WATERS Dolphin surveys have been carried out in Abu Dhabi s coastal waters since 2014 using a 45ft research vessel fitted with an observation platform. Two surveys, each of 15 days duration are conducted during the winter (November - December) and summer (June - July) months each year. The study area is divided into three geographical zones (western, central and eastern) which are characterised by different degrees of human activity. During the surveys, environmental data is collected at regular time intervals and also during dolphin sightings. The method used to estimate the population size is referred to as photo-identification and mark-recapture where the unique pattern caused by cuts, notches and scars on the trailing edge of the dorsal fin are used to identify individual animals. These patterns act as natural tags effectively marking individuals and can be used to identify the dolphins during subsequent surveys. In addition to the estimation of abundance and distribution, the mark-recapture technique also enables us to determine home ranges and site fidelity. Between 2014 and 2017, we surveyed for a total of 64 days at sea covering 5,592 km of survey track. There were 164 encounters (68 with Indian Ocean humpback dolphins, 83 with Indo-Pacific bottlenose dolphins and 13 with finless porpoises). During these encounters we observed 403 Indian Ocean humpback dolphins, 693 Indo-Pacific bottlenose dolphins, and 52 finless porpoises. PAGE 6

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8 APPLICATION OF TECNOLOGICAL INNOVATIONS When moving, it can be challenging to count the total number of individuals in large groups of dolphins from the research vessel. To overcome this, high definition aerial still and video imagery is collected using a drone launched from the boat. This also helps to identify the group structure and number of calves, particularly very young ones that may otherwise be shielded from view by their mother. Additional technological innovations include the development of a specialised application run on an ipad which is used to collect geospatial data in the field and remotely update the central database at the Environment Agency s headquarters. PAGE 8

9 ABUNDANCE OF DOLPHINS IN ABU DHABI The photo-identification and associated mark-recapture study revealed that there was a population of 701 humpback dolphins and 1,834 bottlenose dolphins in Abu Dhabi s coastal waters. What is particularly remarkable from the results is that the population of humpback dolphins in Abu Dhabi is the largest recorded for this species in the world! There were no significant differences in the sighting rates of Indo-Pacific bottlenose dolphins and Indian Ocean humpback dolphins. However, the presence of finless porpoises was significantly lower than for the other two species of small cetaceans highlighting their rarity. The information collected on abundance forms an important baseline which will be used to monitor status and measure the success of conservation management measures in the future. PAGE 9

10 DISTRIBUTION OF DOLPHINS IN ABU DHABI The results of the surveys demonstrated that the Indian Ocean humpback dolphin is an obligate shallow-water species that occurs mostly in the channels and near-shore waters of the Abu Dhabi mainland and islands. The habitat of the Indo-Pacific bottlenose dolphin included both near-shore and deeper off-shore waters. Finless porpoises have a narrow habitat preference and restricted distribution and are very rare. All three species of small cetaceans were encountered during each season surveyed and there were no significant seasonal fluctuations in abundance. Whilst Indo-Pacific bottlenose dolphins were more abundant in the western region deeper water, there were no differences in the distribution of Indian Ocean humpback dolphins and finless porpoises between the different zones. PAGE 10

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12 GROUP SIZE AND COMPOSITION OF DOLPHINS IN ABU DHABI Group size ranged from 1 to 45 individuals for the Indo-Pacific bottlenose dolphin, from 1 to 24 for the Indian Ocean humpback dolphin and from 1 to 12 for finless porpoises. Group composition showed that 78% of Indo-Pacific bottlenose dolphins and 73% of Indian Ocean humpback dolphins were adults. The group size of Indo-Pacific bottlenose dolphins was significantly larger during the winter months compared to the summer, although the Indian Ocean humpback dolphin and finless porpoise group sizes did not vary between seasons. PAGE 12

13 THREATS TO DOLPHINS IN ABU DHABI The analysis of photographs taken during the dolphin sightings helped to determine some of the key threats occurring in Abu Dhabi s coastal waters. A large proportion of dolphins (13% of the Indo-Pacific bottlenose dolphins and 12% of the Indian Ocean humpback dolphins) had cuts and scars on their dorsal fins and/or body. One type of healing pattern observed in both species (4% of Indo-Pacific bottlenose dolphins and 4% of the Indian Ocean humpback dolphins) consisted of straight deep injuries similar to what would be expected from cuts made by monofilament lines or gillnets used in fisheries. Furthermore, 9% of the Indo-Pacific bottlenose dolphins and 8% of the Indian Ocean humpback dolphins had cuts and scarring that were considered to be derived from propellers. Other threats to Abu Dhabi s dolphins include habitat loss from dredging, land reclamation, port and harbour construction, noise pollution and other development activities which are concentrated in the shallow coastal waters and channels. PAGE 13

14 FUTURE OUTLOOK The current dolphin survey has provided baseline population size estimates and information on the distribution, group size and structure and the main threats to resident species. Additional research will help to improve our capacity to define relevant management actions for the conservation of dolphins in Abu Dhabi s coastal waters. We need to understand how specific areas are used by dolphins and what factors affect their distribution and abundance. Genetic studies over a larger area will help in defining population structure and connectivity. In addition to improving the precision of population size estimates through additional surveys, future activities include the development of a conservation management plan for dolphins and small cetaceans in Abu Dhabi. PAGE 14

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16 COPYRIGHT Environment Agency - Abu Dhabi All rights reserved. No part of this report may be reproduced in any material from (including photocopying or storing in any medium by electronic means) without the written permission of the copyright holder. Application for the copyright holders written permission to reproduce any part of this publication should be addressed to the publisher, in accordance with the international copyright Act 1956 and the UAE Federal Law No. (7) Of 2002, concerning copyrights and neighbouring rights, and person acting in contravention of this will be liable to criminal prosecution and civil claims. Photo credits: Environment Agency - Abu Dhabi CONTACT US Environment Agency - Abu Dhabi Call us: (+971) 2 Environment Agency -Abu Dhabi us: customerservice@ead.ae Know more about us: Environment Abu Dhabi Environment Agency -Abu Dhabi