MMRP Lhaviyani Atoll Annual Report 2017

Manta TRUST

Maldivian Manta Ray Project

LHAVIYANI ATOLL | ANNUAL REPORT 2017

Conservation through research, education and collaboration. - The Manta Trust

www.mantatrust.org The Manta Trust is a UK and US-registered charity, formed in WHO ARE THE 2011 to co-ordinate global research and conservation efforts around manta rays. Our vision is a world where manta rays and MANTA TRUST? their relatives thrive within a globally healthy marine ecosystem. The Manta Trust takes a multidisciplinary approach to conservation. We focus on conducting robust research to inform important marine management decisions. With a network of over 20 projects worldwide, we specialise in collaborating with multiple parties to drive conservation as a collective; from NGOs and governments, to businesses and local communities. Finally, we place considerable effort into raising awareness of the threats facing mantas, and educating people about the solutions needed to conserve these animals and the wider underwater world.

Conservation through research, education and collaboration - an approach that will allow the Manta Trust to deliver a globally sustainable future for manta rays, their relatives, and the wider marine environment.

Formed in 2005, the Maldivian Manta Ray Project (MMRP) is the founding project of the Manta Trust. It consists of a country-wide MALDIVIAN MANTA network of dive instructors, biologists, communities and tourism RAY PROJECT operators, with roughly a dozen MMRP staff based across several atolls.

The MMRP collects data around the country’s manta population, its movements, and how the environment and tourism / human interactions affect them. Since its inception, the MMRP has identified over 4,650 different individual manta rays, from more than 50,000 photo-ID sightings. This makes the Maldivian manta population the largest, and one of the most intensively studied populations in the world.

The long-term and nationwide data collected by the MMRP has allowed researchers to record and identify key patterns within this population over time. Not only does this invaluable information improve our understanding of these animals, but it informs their on-going management and protection both in the Maldives, and around the world.

In the last two decades manta and mobula rays have faced THE CONSERVATION increasing threats from both targeted and bycatch fisheries, due in part to a growing trade in Asia for their gill plates. The gill plates are what these rays use to filter zooplankton from the CHALLENGE water. In Traditional Asian Medicine, it is believed these gill plates will filter the body of a variety of ailments when consumed in a tonic. There is no scientific evidence to support this claim.

Manta and mobula rays are particularly vulnerable because of their aggregately behaviour and conservative life-history; they grow slowly, mature late in life, and give birth to few offspring. These traits make it very easy to wipe out entire populations in a relatively short period of time, and slow to recover if protected.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 2 Photo by Guy Stevens

EXECUTIVE SUMMARY

This report presents data collected by the Maldivian Manta Ray Project (MMRP) on Lhaviyani Atoll’s reef manta ray (Mobula alfredi) population between 2004 and the end of 2017.

Reef manta rays are sighted in Lhaviyani Atoll year- local productivity. It is also worth noting that citizen round, but are recorded more frequently toward the end science submissions still play a crucial role in manta ray of the Southwest Monsoon (Oct-Nov) and during the sightings in Lhaviyani Atoll, accounting for 32% of the Northeast Monsoon (Jan-April). During these months, total sightings in 2017. conditions created by the monsoon winds provide an abundance of zooplanktonic food for the reef manta Of the 329 individuals recorded throughout the study, rays locally. Between 2004 and 2016, all data was 83% (n=274) have been re-sighted and 36% (n=118) collected through citizen science and submitted to the have been recorded in different atolls. The Lhaviyani MMRP. In 2017, the MMRP expanded its research base Atoll reef manta ray population demographics is split to include a dedicated researcher in Lhaviyani Atoll. This almost evenly by sex; with 166 (51%) males, to 159 researcher now facilitates a more detailed continuous (48%) females, and with four (1%) individuals for which study of manta rays in Lhaviyani Atoll. the sex could not be determined. Overall, 56% (n=185) of the individuals were adults, 43% (n=140) were Key findings include a total of 1,386 sightings of 329 juveniles, and the maturation stage for the remaining individual reef manta rays recorded at 23 different sites 1% (n=4) of the population could not be determined. in Lhaviyani Atoll throughout 2004-2017. In 2010, there were 333 sightings of 146 different reef manta Over the 14 survey years to date, a large number of rays recorded, the highest number of encounters in reef manta ray sightings (n=342) were recorded at the a single year thus far since records began. In 2017, cleaning stations or surface feeding within Fushifaru during the first year of consistent data collection by a Kandu Marine Protected Area (MPA), located on the MMRP researcher, 239 sightings of 90 different mantas Northeast edge of Lhaviyani Atoll. Manta ray sightings were recorded in Lhaviyani Atoll. This was the second at Fushifaru Kandu peak towards the end of the highest number of sightings recorded in any survey year. Southwest Monsoon (Sept-Nov). Conversely, sightings However, this 2017 sighting high is likely related to a at Dhanifaru, the manta site with the highest number greater level of survey effort by the MMRP researcher, of sightings during the study (n=500), peaked during rather than environmental factors, such as increased the Northeast Monsoon. This seasonal variation is a

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 3 likely result of localised productivity variations within In 2017, in collaboration with the local non- Lhaviyani Atoll, driven by the changing monsoon winds. governmental organisation (NGO), Naifaru Juvenile, a While sighting frequency varied temporally between ten-week Marine Education Programme (Nature Club) these two aggregation sites, it is important to note that was launched, and the resulting curriculum shared demographics of the manta sub-populations at these with the principal of the Lhaviyani Atoll Education sites also varied. Fushifaru Kandu attracts mostly adult Centre. The programme aims to deepen the knowledge mantas, while the majority of the individual manta rays and awareness of young Maldivian students. In light recorded at Dhanifaru were juveniles. of Nature Club’s success in its inception year, the programme has been extended to 2018. A total of 14 pregnant reef manta ray individuals were sighted between 2004 and 2017 in Lhaviyani Atoll. Efforts to conserve the natural heritage of Lhaviyani Atoll The highest number of pregnancies recorded during a and manage the increasing human impacts upon the study year were in 2008 (n=3) and 2014 (n=3), when environment are encouraging, providing much to look respectively 21% and 18% of the mature females forward to in 2018 and beyond. However, it is crucial sighted during those years were observed pregnant. In that active research into manta rays and other marine contrast, only two individuals out of 18 adult females life continues in order to monitor the effects of both (11%) were observed pregnant in Lhaviyani Atoll during tourism and environmental change. Manta rays are an 2017. incredibly important economic resource for the Maldives, bringing tens of thousands of people to the country each The Manta Trust’s ‘How to Swim with Manta Rays’ initiative year to dive and snorkel with them, generating millions was launched in 2017, which adapted the Manta of USD for the economy annually. Being able to pinpoint Tourism Code of Conduct (CoC) into a multi-language the reasons for any observed trends in, or threats to, the 10-Step Guide. This initiative has been disseminated to Maldives manta ray population is crucial for the ongoing tourist operators involved in Lhaviyani Atoll’s manta ray management and protection of these animals. tourism activities. Operators and tourists can now be equipped with the tools and information they need to make their excursions more sustainable.

Photo by Guy Stevens

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 4 UNDERSTANDING THE MONSOONS

Understanding the effects of the Maldives Monsoons is through photosynthesis kick start the food chain, first critical to understanding the reasons for the abundance with phytoplankton, then with zooplankton which of reef manta rays that are seen in Lhaviyani Atoll. predates upon the phytoplankton. Zooplankton is the prey of manta rays (and whale sharks) and as strong The monsoons, which dictate the weather in the lunar currents flow into the shallows of the atolls Maldives, are characterised by their winds, which blow through the channels, the concentrated zooplankton consistently and reverse their direction seasonally. The is so abundant that the Maldivian waters support the Maldives Southwest Monsoon, or Hulhangu, runs from world’s largest known population of reef manta rays. May-October, while the Northeast Monsoon, or Iruvai, runs from December-March each year, with the months Both monsoons attract reef manta rays to the surface of November and April acting as transitional periods of waters of Lhaviyani Atoll. However, sightings peak change in between. The Southwest Monsoon typically towards the end of the Southwest Monsoon and during brings with it much more rain and cloud cover, with the Northeast Monsoon. During a typical Northeast reduced visibility and rougher seas, while during the Monsoon, the wind blows consistently and steadily Northeast Monsoon, seas become calm and clear with from the northeast, causing the greatest concentrations predominantly sunny days. of the manta’s planktonic food on the monsoonal down-current edge of the atoll. Stronger monsoonal During the Southwest Monsoon the strong winds winds generate stronger currents, more upwelling, and in turn create oceanic currents which flow from the more primary productivity, which in turn generates southwest towards the northeast and vice versa during more of the manta’s zooplankton food, attracting the Northeast Monsoon. The Maldivian islands and higher numbers of these animals to feed. When tidal atolls, rising some 2,000 meters from the sea floor, act exchanges bring water from the outside of the atoll in like a barrier to these currents, displacing the water as through the channels they become, temporarily, dense it flows through and around the atolls creating deep- plankton funnels, and it is at these locations where the water upwelling. These upwellings bring nutrient rich greatest concentrations of the planktivorous megafauna water within reach of the suns life giving energy and can be found (Fig. 1).

STUDY PERIOD & SAMPLING METHODOLOGY

2004-2016 SURVEY PERIOD

Between 2004 and 2016, prior to the establishment During this citizen science data collection period, of a full-time MMRP researcher in Lhaviyani Atoll, data manta ray numbers and their prevalent behaviours on manta ray sightings were collected mostly through (feeding, cleaning, cruising, etc.) were noted, as well citizen science. Tour guide operators, dive instructors as trip location and water entry/exit times. Individual and tourists would look for manta rays on both full manta rays sighted underwater were documented and half day surveys. Surveys were conducted in- by photographing the unique spot patterns on their water on SCUBA, or while snorkelling. Prior to 2010, undersides (ventral surface). After the inception only surveys resulting in a confirmed manta ray photo of the MMRP in 2005, photos from each sighting identification (photo-ID) sighting were recorded. It is were submitted to the Manta Trust for identification unknown how many surveys were conducted annually purposes. In the context of this report, a sighting is prior to 2010. However, thereafter all data has been defined as a confirmed photo-ID of an individual manta standardised where possible to produce comparable ray on a given day. results between, and within, years. Between 2010 and 2016, a total of 724 surveys took place (Figs. 2 & 3).

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 5 Figure 1: Map of Lhaviyani Atoll showing the three key manta aggregation sites within the atoll, and Lhaviyani Atoll (black box) in relation to the rest of the Maldives Archipelago.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 6 180

160 153

140 121 120 112 105 100 77 80 80 57 60 50 45 43 Number Number of surveys 34 40 27 20

0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

Figure 2: Number of surveys undertaken monthly in Lhaviyani Atoll (2010-2017).

300 258 250

200 180 158 150

103 100

Number Number of surveys 57 61 48 50 39

0 2010 2011 2012 2013 2014 2015 2016 2017 Year

Figure 3: Number of surveys undertaken annually in Lhaviyani Atoll (2010-2017).

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 7 2017 SURVEY PERIOD

Between the 1st January and the 31st December 2017 During each survey; location, wind speed, current surveys to look for manta rays were carried out in direction, and other environmental weather variables Lhaviyani Atoll on as many days as possible (where were noted alongside manta ray numbers, and the conditions and logistical operations allowed) bya manta’s prevalent behaviours. Individual manta rays MMRP researcher. In total, 180 research trips on 116 were documented using in-water photographic days were made within the survey period (Fig. 4). identification. The majority of data was collected by Resort guests accompanied all trips and the majority MMRP researchers who were experienced freedivers, (93%) were snorkelling excursions, the remainder were allowing them to obtain photo-ID shots whilst ensuring conducted on SCUBA. Manta rays were sighted on minimum disturbance to the animals. This data was 87% (n=157) of the 180 survey trips, however photo- supplemented by additional sighting submissions from ID’s were obtained on only 55% (n=86) of these trips. dive and water sports staff, as well as citizen science Three main manta ray aggregation sites were identified; submissions. Fushifaru Kandu, Huravalhi Finolhu, and Dhanifaru (Fig. 1).

45 42

40 37 34 35

30 25 25

20 14 15

Number Number of surveys 9 10 6 4 5 5 3 0 1 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

Figure 4: Number of surveys undertaken monthly in Lhaviyani Atoll during 2017.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 8 REEF MANTA RAY POPULATION

SIGHTINGS RECORD

A total of 1,386 sightings of 329 individual reef manta the highest number of encounters in a single year thus rays (8% of the total recorded Maldives population) far since records began. In 2017, during the first year were recorded at 23 different sites in Lhaviyani Atoll of continuous data collection by a MMRP researcher, throughout 2004-2017. Eighty nine percent (n=1,229) 239 sightings of 90 different mantas were recorded in of these sightings were recorded during the period Lhaviyani Atoll. Sixty eight percent of these sightings where more detailed survey effort data was also (n=162) were recorded by MMRP researchers, while collected (2010-2017) (Fig. 5). In 2010, there were 333 citizen science submissions account for a total of 77 sightings of 146 different reef manta rays recorded, sightings (32%).

350 3.0

Total 2.4 300 2.5 2.2 Mean

250 333 2.0 200 1.4 1.4 1.3 1.3 1.5 150 1.0 217 239 1.0

Number Number of sightings 100

137 147 0.3 0.5 50 85 59 Mean number of sightings / survey 12 0 0.0 2010 2011 2012 2013 2014 2015 2016 2017 Year

Figure 5: Total annual sightings of reef manta rays (Mobula alfredi) in Lhaviyani Atoll (2010-2017) and the mean number of sightings per survey.

Annual sightings of reef manta rays throughout Monthly breakdown of sightings across all survey years Lhaviyani Atoll have varied over the years. This is likely a (2010-2017), when standardised for effort, show peaks result of both varying survey effort, but also interannual in manta ray abundance in Jan, March-April, and then variations on local productivity. Interestingly, the low again in November (Fig. 6). Monthly breakdown for number of manta sightings recorded in Lhaviyani Atoll 2017 data shows a similar trend (Fig. 7). in 2015 coincided with one of the highest years for manta sightings in Baa Atoll. It may be that increased food availability in Baa Atoll drew a large number of manta rays from Lhaviyani Atoll west.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 9 250 3.0

2.6 Total 2.5 200 Mean 2.1 1.9 2.0 150 1.4 1.2 1.5 1.0 231 214 100 200 1.1 1.1 0.9 0.8 1.0 Number Number of sightings 126 119 0.5 50 98 0.3 0.5 61 71 46 Mean number of sightings / survey 28 8 27 0 0.0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

Figure 6: Total monthly sightings of reef manta rays (Mobula alfredi) in Lhaviyani Atoll (2010- 2017) and the mean number of sightings per survey.

80 1.9 2.0

1.7 1.8 70 1.6 Total Mean 1.6 60 1.3 1.4 50 1.1 1.2

40 1.0 0.5 67 0.8 30 66 49 0.6 Number Number of sightings 20 0.3 0.4 0.2 24 0.2 27 0.1 10 0.0

0.0 0.2 Mean number of sightings / survey 2 1 0 1 1 0 1 0 0.0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

Figure 7: Total monthly sightings of reef manta rays (Mobula alfredi) in Lhaviyani Atoll in 2017 and the mean number of sightings per survey.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 10 This intra-annual variation in sightings can be explained March-April. There is a lull in sightings for five months by variations in the manta ray visitations to the three key before peaking again in Oct-Nov at Fushifaru Kandu in aggregation sites within the atoll (Fig. 8), likely driven the northeast of the atoll. Although this general trend by localised variations in the manta’s zooplankton prey. applies to all years, there is also a significant amount of Annual sightings peak first at Huravalhi Finolhu during interannual variations between the sightings at these Jan-Feb, next is Dhanifaru, where sightings peak during key sites (Fig. 9).

180 160 163

Huravalhu Finolhu 140 Dhanifaru 120 113 101 96 Fushifaru Kandu 100 80 65 67 60 66 32 43 69

Number Number of sightings 37 40 5 34 8 27 47 20 0 3 18 2 3 5 3 12 14 0 1 1 6 0 8 9 38 7 Jan 4 Feb Mar 7 9 Apr May Jun Jul Aug Sep Oct Nov Month Dec

Figure 8: Intra-annual variations in sightings of reef manta rays (Mobula alfredi) in Lhaviyani Atoll at three key aggregation sites (2004-2017).

220 180 Huravalhi Finolhu 160 Dhanifaru

140 147 Fushifaru Kandu 120 83 100 75 80 49 45 87 60 41 7 37 Number Number of sightings 40 31 4 10 16 27 20 44 2 6 0 0 6 0 35 2010 6 8 2011 2012 2013 2014 2015 2016 Year 2017

Figure 9: Interannual variations in sightings of reef manta rays (Mobula alfredi) in Lhaviyani Atoll at three key aggregation sites (2010-2017).

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 11 POPULATION DEMOGRAPHICS

Of the 329 individual reef manta rays which have been been recorded. The slight increase in the percentage recorded in Lhaviyani Atoll from 2004 through 2017, of newly sighted mantas in 2017 is likely a result of the demographics are split almost equally between the increased survey effort, and an increase in the number sexes; with 48% (n=159) females, 51% (n=166) males, of new-born pups, resulting from the increase in and 1% (n=4) of individuals whose sex could not be reproductive fecundity observed throughout the determined (Fig. 10). The population demographics Maldives reef manta population in recent years. Indeed, was slightly more biased towards adults than juveniles, of the 23 new individual reef manta rays recorded in with 56% (n=185) of individuals recorded as adults, Lhaviyani in 2017 (26% of the sighted individuals), five while 144 (44%) of individuals were juveniles. were estimated to be young of the year, based on their small disc widths. Of the remaining 18 new mantas, 11 As expected, the proportion of newly sighted individual had never been recorded anywhere in the Maldives by reef manta rays recorded annually has followed a the MMRP, while the remaining seven individuals had downward trend over the study years as more of the previously been recorded in other atolls. population is identified (Fig. 11). As the years have passed more data has been collected and sightings of new manta rays have become less frequent. To date, 83% (n=274) of the atoll’s reef manta ray population has been re-sighted, suggesting the vast majority of the individuals which frequent this atoll have now

4 1%

144 159 44% 166 48% 185 51% 56%

Juvenile Adult ♀ ♂ Unknown

Figure 10: Demographics of the Lhaviyani Atoll reef manta ray (Mobula alfredi) population (n=329).

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 12 160 100% 146 90% 140 Total individuals New individuals 80% 120 106 70% 100 90 90 87 60%

80 50%

61 60 40% 60

Number of individuals 30% 38 38

40 Percentage new individuals 20% 15 20 12 9 10% 3 0 0 0% 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Year

Figure 11: Total number of individual reef manta rays (Mobula alfredi) sighted annually in Lhaviyani Atoll (2004-2017), and the percentage of those individuals which were newly recorded.

INTER-ATOLL MIGRATIONS

Thirty six percent (n=118) of the population of reef Noonu) with 18 different individuals. In total, mantas manta rays in Lhaviyani Atoll have been recorded which have been recorded in Lhaviyani Atoll have also in multiple atolls (Fig. 12). The most common inter- been recorded in 12 other geographical atolls. This high atoll movement records are, unsurprisingly, between degree of migration between the atolls is reflective of Lhaviyani and those atolls closest to it geographically, the wider population. With relatively small distances but also those atolls where the MMRP has the most (10s km) between the atolls in the central and northern intensive data collection effort. Not surprisingly regions of the Maldives, and shallow maximum ocean therefore, toping this list is Baa Atoll, with 77 individuals depths (<300m) between most of these atolls, there are with sighting records in both atolls. Raa Atoll comes limited barriers to migration. Indeed, several individuals second, with 24 individuals, followed by the northern have been recorded travelling back and forth between atoll of Thiladhunmathi (collectively the combined Baa and Lhaviyani Atolls multiple times in a season. political atolls of Haa Alifu, Haa Dhaalu, Shaviyani and

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 13 I-Hippo 0 T-mathi 18 Raa 24 Fasdhu 8 Baa 77 Goidhu 1 N-Malé 12 S-Malé 3 Thoddu 0

Rasdhu 1

Atoll Ari 15 Vaavu 2 Vattaru 0 Meemu 1 Faafu 0 Dhaalu 0 Thaa 0 Laamu 3 Gaafu 0 Addu 0

0 10 20 30 40 50 60 70 80 Number of individuals

Figure 12: Number of reef manta rays (Mobula alfredi) from within the Lhaviyani Atoll population (n=329) which have been recorded in other atolls throughout the Maldives Archipelago.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 14 ATOLL RESIDENCY

Although many of the individual manta rays recorded times each respectively. Both are females, although in Lhaviyani Atoll have been recorded travelling to Feng Shui is a mature female, while Crusty is a sub- other atolls, the majority (64%) (n=211) have only been adult. A heat map (Fig. 13) of the sightings of these recorded within Lhaviyani, suggesting a high degree two mantas illustrates how site fidelity varies between of site fidelity. Indeed, many individuals have been individuals, even within the atoll. Feng Shui has been recorded consistently over the years, often being re- sighted mostly at Fushifaru Kandu and Dhanifaru, while sighted at the same location over a dozen times. Two the majority of Crusty’s sightings occur at Huravalhi individuals in particular, MV-MA-0041 (Feng Shui) and Finolhu. MV-MA-1182 (Crusty), have been sighted 35 and 34

Photo by Guy Stevens Photo by Guy Stevens

MV-MA-0041 (Feng Shui), sighted on 20th February 2008. MV-MA-1182 (Crusty), sighted on 24th November 2012. She is a mature female, and has been sighted a total of 35 She is a sub-adult female, and has been sighted a total of times, mostly at Fushifaru Kandu and Dhanifaru. 34 times, mostly at Huravalhi Finolhu.

Overall, the degree of site fidelity to Lhaviyani Atoll by Index (RI) was calculated for each year post-2010, the reef manta ray population is hard to calculate due based on the ratio between the number of days each to inconsistent survey effort over the years. However, individual was sighted and the total number of surveys the greater consistency of data collection from 2010 (e.g. a RI of 3% means that, on average, each individual onward enables some preliminary analysis (Fig. 14). was sighted on 3% of the total surveys). The RI results Throughout 2017, each manta was observed on for 2017 (1.5%) were similar to previous years, and average 2.7 times, a slight increase from previous years considerably lower than the highest calculated RI of of citizen science data collection. However, to account 3.6%, recorded in 2013 (Fig. 15). for varying survey effort interannually, a Residency

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 15 Figure 13: A heat map of the sightings (n=69) of two female reef manta rays (Mobula alfredi) in Lhaviyani Atoll between 2004 and 2017.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 16 3.0 70%

61% 60% 2.5 51% 43% 50% 2.0 38% 38% 40% 33% 34% 1.5 2.3 2.7 30% 2.0 1.0 1.7 20% 1.6 1.5 1.4 0.5 1.0 10%

0% individuals Percentage sighted >1 of

Mean Mean number of sightings / individual 0.0 0% 2010 2011 2012 2013 2014 2015 2016 2017 Year

Figure 14: Mean number of sightings per individual reef manta ray (Mobula alfredi) in Lhaviyani Atoll (2010-2017), and the percentage of individuals sighted on multiple occasions during the same year.

4.0% 3.6% 3.5%

3.0% 2.7% 2.5% 2.5% 2.1% 2.0% 1.6% 1.5% 1.5% 1.3% Residency index 1.0% 0.9%

0.5%

0.0% 2010 2011 2012 2013 2014 2015 2016 2017 Year

Figure 15: Annual Residency Index (RI) of the reef manta rays (Mobula alfredi) in Lhaviyani Atoll (2010-2017). RI is calculated as the average of each individuals’ residency score (= number of times sighted annually divided by the total number of surveys).

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 17 MARINE PROTECTED AREAS

On the 6th December 2017, a proposal for the creation rays (Fig. 17). Nursery grounds are critical habitats for of two new marine protected areas (MPAs) (Huravalhi the successful growth and survival of neonate and Finolhu and Dhanifaru) within Lhaviyani Atoll was juvenile manta rays, and therefore need protection presented to the Lhaviyani Atoll Council by a MMRP and effective conservation management. Legislating researcher in collaboration with Naifaru Juvenile, Dhanifaru and Huravalhi Finolhu as MPAs would help another local NGO. Huravalhi Finolhu and Dhanifaru to safeguard a significant area of key habitat for this are key manta ray aggregation sites, which, together species within Lhaviyani Atoll, encompassing adult with the already projected Fushifaru Kandu, account for and juvenile aggregation areas as well as feeding and 81% (n=1123) of the total sightings (n=1386) recorded cleaning sites. to date in Lhaviyani Atoll (2004-2017) (Fig. 16). However, protective legislation alone will not suffice. Dhanifaru and Huravalhi Finolhu are primarily feeding Effective management plans also need to be putin sites, however there is also a cleaning station, known place for any new MPAs, and the existing protected locally as ‘Manta Rock’, at Dhanifaru. Interestingly, a areas (Fushifaru Kandu and Kuredu Kandu) are also much larger proportion of the reef manta ray sightings in need of better management to safeguard against at Dhanifaru since 2004, when compared to the unsustainable tourism and fishing activities. As tourism other key aggregation sites, have been of juveniles, and development continues to rapidly grow in the suggesting this area serves as an important nursery Maldives, it is essential these management plans are ground. In contrast, Fushifaru Kandu and Huravalhi created and effectively enforced. Finolhu are frequented primarily by adult reef manta

281 20%

342 500 25% 36%

263 19%

Dhanifaru Huravalhi Finolhu Fushifaru Kandu Other

Figure 16: Proportion of total reef manta ray (Mobula alfredi) sightings at the three key manta aggregation sites in Lhaviyani Atoll (2004-2017).

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 18 300 Adults Juveniles 254 246 250 230 218

200

150 112 100 63 Number of individuals 50

0 Dhanifaru Huravalhi Finolhu Fushifaru Kandu Aggregation site

Figure 17: Total number of sightings of adult and juvenile reef manta rays (Mobula alfredi) at the three key manta aggregation sites in Lhaviyani Atoll (2004-2017).

COURTSHIP & REPRODUCTION

Throughout their range globally, manta ray reproductive A total of 14 pregnant reef manta ray individuals were activity often peaks at particular times of the year. sighted between 2004 and 2017 in Lhaviyani Atoll. In the Maldives, courtship behaviour and mating are The highest number of pregnancies recorded during a much more frequently observed during the months study year were in 2008 (n=3) and 2014 (n=3), when of Oct-Nov, and again in Mar-Apr, when the country’s respectively 21% and 18% of the mature females sighted two monsoons (seasons) transition from one to the during those years were observed pregnant (Fig. 18). In other. Throughout the day, adult manta rays spend a contrast, only two individuals out of 18 adult females significant amount of their time cleaning, with female (11%) were observed pregnant in Lhaviyani Atoll during mantas often spending several hours each day cruising 2017. The proportion of pregnant individuals among around a favoured cleaning site. Cleaning stations Lhaviyani Atoll’s population is consistent with records therefore often become the focal point for courtship from elsewhere in the Maldives and indicates an overall and mating activity. It is thought that receptive females very slow reproductive rate. With such low fecundity, release pheromones in order to signal to a potential it is vital to minimise anthropogenic and natural mate their readiness to reproduce. In Lhaviyani Atoll, impacts to this species. Effective measures include the although there is limited data on courtship activity, all establishment of functional MPAs and the adherence to events (n=6) have been recorded during the change sustainable tourism activities at key manta ray mating, between the Southwest and Northeast Monsoons, cleaning, and feeding sites. in the months of Sept-Dec, all of which have been documented at the cleaning station in Fushifaru Kandu.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 19 24 23 Adult females 22 22 Pregnant females 20 20 19

18 18 17 16 16 14 14 12 10 8 5

Number of individuals 6 4 4 3 3 2 2 2 2 2 2 1 1 0 0 0 0 0 0 0 0 0 0 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 Year

Figure 18: Total number of adult female reef manta rays (Mobula alfredi) sighted annually in Lhaviyani Atoll, and the total number of those females which were recorded pregnant in the same year (2004-2017).

Photos by Lisa Bauer

A pregnant female manta ray (left) spotted in Huravalhi Finolhu in March 2017, and a newborn female pup (right) spotted in Dhanifaru exactly three weeks later.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 20 SUB-LETHAL INJURIES

Approximately 33% (n=108) of the Lhaviyani Atoll reef attributed to anthropogenic origins (e.g. fishing line manta population (n=329) have some form of sub-lethal entanglement, boat strike, etc.). The remaining 10 injury, which is higher than the national average of 28%. injuries (<1%) were from an undetermined origin (Fig. In total, there were 116 separate injuries recorded, with 20). The majority of the anthropogenic originated most individuals having just one injury, while eight had injuries resulted from fishing line entanglements, two distinct injuries from separate origins. The number while the majority of the natural injuries resulted from of injuries is split almost evenly between males and predatory bites. In both instances, the vast majority of females, and perhaps unsurprisingly, injuries are more the resulting injuries effected the manta’s pectoral fins common on adults (which are older and therefore likely (Fig. 21). to have encountered threats more often) than juveniles (Fig. 19). Approximately 66% (n=70) of the recorded injuries were attributed to natural origins (e.g. predatory bites, disease, deformity, etc.), while 34% (n=36) were

70 25 60

50 17 19 40

30 50 11 20 Number of individuals 35 35 10 20

0 Females Males Adults Juveniles

Natural Anthropogenic

Figure 19: Demographic variations in the number of sub-lethal injured (n=108) reef manta rays (Mobula alfredi) within the Lhaviyani Atoll population (n=329), and likely injury origin (natural or anthropogenic).

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 21 70 66

40 32 30

Number of individuals 10 10 3 4 1 0

Injury origin

Figure 20: Variations in the origin of sub-lethal injuries (n=116) within the injured reef manta ray (Mobula alfredi) population of Lhaviyani Atoll (n=108).

About 66% of the sub-lethal injuries seen in Lhaviyani’s mantas are natural in origin - with most of them being attributed to predatory bites, often from sharks.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 22 100% 0 0 2 2 6 8 90% 9 7 8 80% 9 5 4 70% 60% 50%

40% 49 67 43 25 30% 20% 10% Percentage Percentage of injured individuals 0% Females Males Adults Juveniles

Pectoral fin Cephalic fin Dorsal or tail Gill slits

Figure 21: Variations in the location and number of sub-lethal injuries (n=116) within the injured reef manta ray (Mobula alfredi) population of Lhaviyani Atoll (n=108), and their demographic variation (actual number of injuries on bars).

Although only recorded on three mantas in Lhaviyani, injuries from boat-strikes are some of the most recognisable. Mantas are sometimes hit when they are feeding near the surface, and often its the propellor that inflicts the real damage on the animal.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 23 Photo by Guy Stevens

WHALE SHARK & OCEANIC MANTA RAY SIGHTINGS

Whale sharks (Rhincodon typus) reflect similar life The Maldives Whale Shark Research Programme history characteristics to manta rays. Both are large, (MWSRP) recognised WS-310 as a newly identified migratory, filter-feeding elasmobranchs. Additionally, individual as a result of this sighting. the two species share common habitat use and are often sighted together. Two sightings of whale sharks Oceanic manta rays (Mobula birostris), capable of (WS-310 and an unidentified individual) were reported growing up to seven metres in wingspan and living during 2017 in Lhaviyani Atoll. Both sightings occurred further offshore, are the larger ‘cousins’ of their reef at the same location (Kanuhuraa Beyru) during months manta relatives. Oceanic manta ray sightings are not with peak abundances in plankton and surface feeding common in Lhaviyani Atoll; only three sightings of three manta rays (March and October). Moreover, local different individuals (MV-MB-0224, MV-MB-0243 fishermen reported sighting several whale sharks in and MV-MB-0244) have been recorded to date. The deep water outside the atoll during the same months. first of which was sighted in November 2016, with the remaining two oceanic manta rays sighted in the Both of the sighted whale sharks were juveniles (~3m Fushifaru Kandu area in December 2017. The three in length). However, as the second whale shark could individuals were all adults; two males and one female, not be identified, it is possible it could have been a and all were new to the Manta Trust database. resighting of WS-310, rather than a separate individual.

Photo by Guy Stevens

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 24 ENVIRONMENTAL VARIABLES

Limited environmental data was recorded during the future, it would be more accurate to use environmental manta ray surveys conducted prior to 2017. However, data collected locally. historic weather data (2010-2017) was sourced from the Maldives meteorological department to elucidate Interestingly, when the same wind data is used to any potential relationships between manta ray sightings compare wind speed with manta sightings by month in Lhaviyani Atoll, and the strength of the wind from instead of annually, an inverse correlation emerges 2010 onward (Fig. 22). The highest average annual wind (Fig. 23). During the Northeast Monsoon months, speeds were recorded in 2010 and in 2016, measuring when the average wind speed is at its lowest, the 17.4 km/h and 17.2 km/h respectively. However, these highest number of manta sightings occur. This inverse peaks did not correspond to the years with the highest correlation is likely a result of the localised productivity number of manta sightings per survey (2012 & 2013). within Lhaviyani Atoll, which unlike in the nearby atoll In other atolls, where more intensive and detailed data of Baa (which sees greater manta sightings during the collection is recorded, there is a significant correlation Southwest Monsoon on the atoll’s east coast), creates between increased average wind speed and increased more upwelling and feeding opportunities in the atoll manta ray sightings. It is also worth noting that the wind channels during the Northeast Monsoon. data used in this analysis is based on the Malé weather station, 110 km to the south of Lhaviyani Atoll. In the

20 3.0 Average wind speed 19 2.4 Number of mantas 2.5

18 2.2

17 16.3 17.4 16.1 16.2 2.0 17.2 16 16.1 1.4 1.4 15 1.3 1.3 1.5 15.3 1.0 14 14.5 1.0

Wind speed (km/h) 13

12 0.3 0.5 11 Mean Mean number of rays manta per survey 10 0.0 2010 2011 2012 2013 2014 2015 2016 2017 Year

Figure 22: Mean annual wind speed (km/h) and mean number of reef manta rays (Mobula alfredi) sightings per survey in Lhaviyani Atoll (2010-2017).

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 25 22 3.0 2.6 Average wind speed 20.1 Number of mantas 20 2.5

2.1 17.9 17.8

1.9 18 18.8 18.9 17.4 2.0

16.0 16 1.5 1.2 16.4 1.4 1.1 1.1 0.9 14 0.8 1.0 Wind speed (km/h) 1.0 14.4 0.5

11.8 0.3 12 12.8 0.5

11.5 Mean number of rays manta per survey 10 0.0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

Figure 23: Mean monthly wind speed (km/h) and mean number of reef manta rays (Mobula alfredi) sightings per survey in Lhaviyani Atoll (2010-2017).

At all sites surveyed in 2017 environmental data on atoll channels was recorded on 150 of these. These the current direction was compared to the primary preliminary results support the hypothesis that manta behaviour being undertaken by the observed manta rays are much more likely to be observed both feeding rays in order to seek correlations for this behaviour. and cleaning when the current is flowing out of the During the 157 surveys were reef manta rays were atoll channels (Fig. 24). observed, data on the current direction through the

100% 6 1 90% 80% 9 70% 16 60% 83 Slack 50% Out 40% In 30% 7 20% 7 Percentage of surveys 10% 21 0% Feeding Cleaning Cruising Manta behaviour

Figure 24: Changes in behavioural activity of reef manta rays (Mobula alfredi) in relation to current direction (In, Out, Slack) through the channels of Lhaviyani Atoll during 2017 surveys when mantas were observed (n=150).

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 26 Photo by Nong

TOURISM ACTIVITIES

The average number of tourist vessels recorded per the Best Practice Code of Conduct (CoC) in 2014, aimed survey has doubled between the survey years of at minimising tourism activities’ impact on the natural 2010-2017. Although this number varies considerably behaviour of manta rays in the Maldives. The Manta between years, there is an increasing trendline for Trust CoC has been implemented by various operators tourism activities at the manta aggregation sites in in the country, and they aim to keep disseminating it Lhaviyani Atoll (Fig. 25). Conversely, the average with the support of the Maldives government. number of snorkellers per vessel has decreased over the same survey period (Fig. 26). Variability in survey In 2017, the Manta Trust also launched the ‘How to effort is likely to account for some of the variation, as Swim with Manta Rays’ initiative, which has adapted the MMRP researcher is based on a high-end resort the Manta Tourism CoC into a multi-language 10- where guests activities are often run with much lower Step Guide, for both snorkelers and divers, and a short guest numbers. educational film. This freely-available media kit aims to deliver a pertinent message on sustainable tourism Manta rays are of significant economic value to the and has already been adopted by a growing list of Maldives economy. As resort, guest house, and tour operators throughout the Maldives. The ‘How to liveaboard guests continue to visit the country to Swim with Manta Rays’ initiative has its own dedicated snorkel or dive with these charismatic animals in website (www.swimwithmantas.org), where operators increasing numbers, the Maldives reef manta ray and tourists can become equipped with the tools and population generates tens of millions of USD for the information they need to make their excursions truly local economy annually. With increasing popularity sustainable for the Maldivian reef manta rays. of manta ray interactions, it becomes evident that anthropogenic pressures on manta rays are increasing as well. In response, the Manta Trust released a guide for

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 27 2.2 2.0

2.0 1.9 1.8 1.6 1.6 1.4 1.3 1.3 1.3 1.2 1.2 1.0 1.0 0.8 0.6 0.4 0.2 Average number Average of boats / survey 0.0 2010 2011 2012 2013 2014 2015 2016 2017 Year

Figure 25: Average number of tourism boats per survey (n=904) in Lhaviyani Atoll (2010-2017).

16 14.4 14.2 14 12.7

12 11.0 10.4 10.0 10

8.0 8 6.9 survey 6

2 Average number ofsnorkellers / 0 2010 2011 2012 2013 2014 2015 2016 2017 Year

Figure 26: Average number of snorkellers per survey (n=904) in Lhaviyani Atoll (2010-2017).

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 28 LHAVIYANI ATOLL MARINE EDUCATION PROGRAMME

In 2017, in collaboration with the local NGO Naifaru The Marine Education Programme was well received Juvenile, a ten-week Marine Education Programme by students and teachers alike. It aimed to deepen was created, and the resulting curriculum shared with the knowledge and awareness of young Maldivian the principal of the Lhaviyani Atoll Education Centre. students that already showed an interest in the natural As part of a voluntary after-school activity, Nature environment. It also supplemented the scientific Club students on the island of Hinnavaru met up once curriculum by presenting biology topics with a focus on a week and were taught basic marine biology and the Maldives tropical marine environments. Thanks to conservation information during interactive classroom the logistical support of Hurawalhi Resort and Prodivers, sessions. Each session was completed with a task to test the Manta Trust’s Lhaviyani Project Manager was able to the students acquired knowledge and inspire creative actively participate throughout the whole programme. thinking. Students had to actively participate further During 2018, the Manta Trust researcher and staff from by presenting their own ideas and group work in front Naifaru Juvenile plan to expand on 2017’s programme of the class. A field excursion to Hurawalhi Resort was topics, and continue to actively participate in numerous also organised, where students and teachers had the other environmental initiatives in Lhaviyani Atoll. opportunity to learn about sustainability practices and native plants. The final session of the programme saw an educational beach clean-up before the certificates were handed out to the successful participants.

Students from Hinnavaru during a Nature Club visit to Hurawalhi Resort, learning about sustainability practices and native plants.

Photo by Lisa Bauer

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 29 Additional photos from several environmental initiatives that the Manta Trust researcher and staff from Naifaru Juvenile attended, including; the Hinnarvaru school visits (top and middle), the Lhaviyani Turtle Festival (bottom left), and Moodhu Makaan’du Festival (bottom right). Photos by Lisa Bauer, Kirsty Ballard, Prodivers, and Hurawalhi Island Resort & Spa.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 30 This report was produced by:

MALDIVIAN MANTA RAY PROJECT (MMRP)

The MMRP is highly regarded within the scientific community. It is the largest and one of the longest running manta ray research programmes in the world. We would welcome the opportunity to continue to work with the Maldives government for the long-term management and conservation of these species in Maldivian waters. The opportunity we have to learn about manta rays in the Maldives is unique, and our findings have important implications for manta ray conservation on a global scale.

The MMRP and the Manta Trust are happy to share with the Maldives government data collected as part of this study.

ACKNOWLEDGEMENTS

The MMRP and the Manta Trust are extremely grateful to all our partners who enable our team to carry out our fieldwork throughout the year. We are also extremely thankful to all those members of the public, dive staff, marine biologists and other manta enthusiasts who submit images of manta rays from around the country to be added to our national database. Without this continued support, our work would not be possible.

MANTA TRUST | Lhaviyani Atoll Annual Report 2017 31 This report was compiled on behalf of the MMRP and the Manta Trust by:

Kirsty Ballard - BSc (Hons), MSc (Hons): Tam Sawers - BSc (Hons), MSc (Hons): Project Manager - Lhaviyani Atoll (2017-2018) Project Leader - Maldivian Manta Ray Project

Lisa Bauer - BSc (Hons), MSc (Hons): Dr. Guy Stevens - BSc (Hons), PhD: Project Manager - Lhaviyani Atoll (2016-2017) Chief Executive / Founder - The Manta Trust

For further information, please email:

[email protected] [email protected] [email protected]

Document created by: Danny Copeland

The information and ideas within this document are the intellectual property of the Manta Trust. Any scientific data, general concepts or ideas distributed to our collaborators and partners belongs to the Manta Trust and are not to be shared with a third party without prior permission from the Manta Trust.