Manta Project Fiji Impact Report 2023

Manta Project Fiji
Impact Report
2023
Manta
T R U S T

Contents
CORE PROJECT SITES
Project Overview
Mobula Ray Species
The Yasawa Islands
North Kadavu Region
Wakaya Island
Laucala Bay, Suva
The Lau Group
Student-Led Project
04
06
08
10
12
14
16
18
20
In the media
Thank you
Manta
T R U S T
24
26
Manta Project Fiji is a proud affiliate of the Manta Trust,
working towards
Mobulid Conservation
through Research, Education & Collaboration

COre Project Sites
Yasawa
Islands
Wakaya Island
Suva
The Lau
Group
North Kadavu
REGION

2023 saw the 11th year of data collection on mobulid rays across the country. While we celebrate the
expansion of the project into new research areas and conservation initiatives, we remain conscious that
much work still needs to be done to better understand the vulnerability of this species group within Fiji
waters.
Baseline data collection continued at the project’s core sites in the Yasawa Islands at Barefoot Manta
Island Resort and in the North Kadavu Region at Kokomo Private Island Fiji, with photo identification,
environmental and anthropogenic data collected on all manta ray surveys. During 2023 our partnership with
Wakaya Island Resort was strengthened allowing increased surveys and baseline data collection around
Wakaya Island in the Lomaiviti Group of islands, an area with historically sparse data coverage.
Project Overview
2023
Baseline data collection also increased in the Suva area and in the remote Lau group in partnership with
Conservation International. Both these habitat areas are unique in that mutliple species of mobula ray are
sighted in these areas, giving the teams an opportunity to better understand some of the species we still know
very little about.
1060 Manta Surveys
Conducted
2 NEw core data
collection sites added
The 12th year of data collection for
Manta Project Fiji
1561 Manta Sightings
Recorded
7 Satellite Tags Deployed
Awareness & Education
delivered to 2500+ individuals
Across our survey sites we recorded 1561 manta ray sightings, an increase of 165 sightings when compared
to the 1396 sightings recorded throughout 2022. Increasing baseline data collection across the country is
still of priority due to many geographic areas being under represented in the sighting records.
Seven satellite tags were deployed across the country to help better understand broad-scale movement
ecology and critical habitat use of Fiji’s reef manta ray population. Tags were deployed in the Lau and
Lomaiviti group of islands, areas which we have very little information on the populations that inhabit the
waters.
Awareness workshops and educational lectures were delivered to a wide range of demographics including
university students, communtiy members, government officials, tourists and resort staff. We hope to
increase our outreach in 2024 and innovate on specific ways to engage different audiences.
A new student-led project was completed in 2023 from the University of the South Pacific, an exciting step
forward in our continued effort to support mobulid research led by University students and staff.

Mobula Ray Species
Mobula rays are some of the largest and most intelligent fish in the ocean. These cartilaginous filter feeders are found throughout the tropical and sub-tropical oceans of the world. Currently in Fiji
five mobula species have been identified, two species of manta ray; the oceanic manta ray (Mobula birostris) and the reef manta ray (Mobula alfredi), and three species of devil ray; the bentfin devilray
(Mobula thurstoni), the sicklefin devilray (Mobula tarapacana) and the spinetail devilray (Mobula mobular).
Manta Rays
Reef manta rays are the most common mobula ray sighted around Fiji, being monitored at
many well known aggregation sites. Oceanic manta rays are only known to aggregate at one
site in the country, however sporadic sightings have been recorded across the country.
Devil Rays
Very little is known about the three species of devil ray documented in Fiji. Since 2012 only a
handful of sightings exist from the Yasawa Islands, Namena Island and the Lau Group.
Vulnerable
Endangered Endangered Endangered Endangered
Reef Manta Ray
(Mobula alfredi)
Oceanic Manta Ray
(Mobula birostris)
Sicklefin Devil Ray
(Mobula tarapacana)
Spinetail Devil Ray
(Mobula mobular)
Bentfin Devil Ray
(Mobula thurstoni)
Manta illustrations throughout document by Marc Dando

the Yasawa
islands
The Manta
Channel
Key Partner
Barefoot Manta
Island Resort
Barefoot Manta Island Resort has been an integral
partner of Manta Project Fiji since 2012. As our
initial partner in country Barefoot Manta Island
Resort has contributed significantly to the research
efforts within the Yasawa Islands, leading the way
towards sustainable manta ray encounters at the
Manta Channel.
The main reef manta aggregation site is just off the
island, where strong currents funnel zooplankton
into the shallow channel between Drawaqa and
the largest island in the Yasawas, Naviti. Barefoot
Manta staff and MPF researchers collect daily data
on the manta rays sighted, building an invaluable
data set which will allow effective management
strategies to be developed.
Project Overview
The Yasawa Islands are made up of 11 main volcanic islands running 90 km
to the North-East of Fiji’s main island, Viti Levu. These islands are one of Fiji’s
busiest tourist destinations and attract almost 90,000 visitors every year. The
Manta Channel is located towards the southern end of the island chain between
Drawaqa Island and the largest island in the chain, Naviti Island. This small
channel is approximately 250m long, 300m wide and 7m deep at high tide in the
deepest section. The channel is dominated by hard coral and is subject to high
currents during the daily tidal fluctuations.
During the cooler drier months from April through to October reef manta rays
(Mobula alfredi) aggregate at the Manta Channel to forage on dense zooplankton.
Since 2012 we have collected photo identification data on the manta population
along with environmental and anthropogenic data. This data allows us
to monitor the population dynamics and demographics over time as well as allowing
us to gain an insight into population 2022-2023
connectivity and movement ecology.
Environmental and anthropogenic data allows us to monitor the environmental
conditions that create favourable foraging conditions and importantly allow us
to monitor the interactions between the tourism industry and manta ray
sightings.
No. of
Days
200
150
141
100
50
0
Annual Survey
Days
205
162 170 153
215 224 230 201 190
2013 2014 2015 2016 2018 2019 2020 2021 2022 2023
Percentage
100
90
80
70
60
50
40
30
20
10
0
79% 82% 68%
Reef Manta Ray
(Mobula alfredi)
78%
54%
58% 63% 60%
Percentage of Survey
Days Manta Rays
Sighted
70%
Average Number of Snorkelers
58%
2013 2014 2015 2016 2018 2019 2020 2021 2022 2023
As the busiest tourist destination for manta ray watching in Fiji, the Manta Channel is subject to
heavy anthropogenic pressures, such as snorkelling and boat traffic. A correlation does not
necessarily indicate causation however there is a clear negative correlation between the average
number of snorkelers visting the site per day vs the number of manta rays sighted. During 2023
we recorded 213 manta ray sightings of 27 different manta rays, with an average of 41 snorkelers
in the Manta Channel.
55
2013
2014
2015
2016
2018
2019
2020
2021
48
2022
2023 43
41
COrrelation = causation?
Numbers display average
number of snorkelers with
manta rays
36 36
Average number of snorkelers
VS
45
42
Annual Manta Ray Sightings
0
0 Number of Manta Ray Sightings
600
2023 in review
Surveys were conducted on 190 days between April - October
Manta rays were sighted on 58% of survey days
199 drone flights were conducted
2013 - 2019 and 2023
display much higher
average numbers of
snorkelers with a much lower
number of manta ray
sightings
We recorded 213 manta ray sightings. This is one of the lowest annual
sighting totals on record, a 64% reduction when compared to 2022.
27 different manta rays were recorded, a 50% reduction when
compared to 2022
The top five sighted manta rays made up 72% of all sightings in 2023
There were an average of 41 snorkelers in the water when manta rays
were present, one of the highest on record
169 (79%) sightings were of female manta rays and only 44 (21%) of
male manta rays
3
18
2020 - 2022 display much
lower numbers of
snorkelers with a much
higher number of manta ray
sightings
4

The Population
Sex Demographics
Male
Female
Percentage
Unknown
The Kadavu sub-population is split almost
50-50 between males and females.
There is a slight majority of males with
53% of manta rays being male and 46%
being female and 1% being of unknown
sex.
183 Manta Rays
Melanistic
Chevron
Percentage
color morph demographics
The Kadavu sub-population displays
one of the lowest melanism proportions
in Fiji with only 34% of manta
rays being melanistic and 66% being
chevron.
North Kadavu
Region
Yaukuve Island
Group
Vuro Island
Key Partner
Kokomo Private
Island Fiji
Manta Project Fiji and Kokomo Private Island Fiji started
collaborating in 2019 to better understand manta ray
population dynamics, demographics and movement
ecology in the region.
Two main research sites exist in the region, Vuro Island,
which is a shallow cleaning habitat for manta rays and the
Yaukuve Island Group, a primarily foraging habitat for
manta rays.
Project Overview
Reef Manta Ray
(Mobula alfredi)
Kadavu is the third largest island in Fiji and is in the southern region,
approximately 75km from Suva. Kadavu and nearby islands are surrounded by
the Great Astrolabe Barrier Reef system which extends over 100km along the
eastern side and encloses the entire northern region within a lagoon. The
primary survey area encompasses the whole north Kadavu region from Ono to
Solo Reef.
Kadavu attracts a much smaller number of tourists when compared to the
Yasawa Islands, most likely due to its harder to reach location. Kadavu typically
attracts less than >4% of Fiji’s visitors. However, due to the luxury status of
multiple resorts, the region sits much closer to the revenue power of the
Yasawa Islands.
The primary survey area encompasses multiple islands and a large reef system
where manta rays can be sighted year round, however, sightings
typically peak between May and November every year. Both cleaning and
foraging habitats are surveyed in this region.
250
200
150
100
50
0
66
Annual Survey
Days
203
227 233 231
2019 2020 2021 2022 2023
100
90
80
70
60
50
40
30
20
10
0
55%
90% 89%
2023
2022
2021
2020
Percentage of survey
days manta rays were
sighted
120 sightings were of
foraging behaviour
82%
94%
2019 2020 2021 2022 2023
Sighting Variation
642 sightings were of
cleaning beahviour
802
Sightings
542
Sightings
1041
Sightings
1027
Sightings
2019
514
Sightings
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
2023 in review
28 sightings were
courting behaviour
Surveys were conducted on 231 days between April - November
Manta rays were sighted on 94% of survey days
80 drone flights were conducted
804 manta ray sightings recorded
131 different manta rays were recorded
Manta sightings peak
between April - November
every year. During 2023
manta sightings peaked
during June and July.
We recorded 802 manta
sightings during 2023,
significantly more than
both 2019 and 2022,
however this is still 200
sightings less than both
2021 and 2020
428 (53%) sightings were of female manta rays and 373 (47%) of
male manta rays
There were an average of 5 snorkelers in the water when manta rays
were present

We have recorded four different
manta rays making a migration
between Wakaya Island and the
Yasawa Islands
Photo ID - Migration
Manta Channel,
The Yasawa Islands
Approx. 260km
Wakaya
Island
Image by Tom Vierus
Wakaya Island
Wakaya Island
Key Partners
Project Overview
Reef Manta Ray
(Mobula alfredi)
Wakaya Island is part of the Lomaiviti Group of islands situated to the east of
Viti Levu. Wakaya Island is surrounded by an extensive reef system and large
lagoon on the eastern side, on the western side the island is fringed by a deep
channel dropping to over 900m deep. This deep channel funnels strong currents
and nutrient rich water into the reefs and lagoons, creating perfect conditions
for manta rays to both forage and clean.
After sporadic data collection from citizen scientists over the years, Manta
Project Fiji and Wakaya Island Resort began working together very closely in
2023 to better understand the manta population found around Wakaya Island.
At a similar time the NAI’A liveaboard who also dive Wakaya’s coral reefs began
submitting consistent manta identification data taken on their trips.
Satellite Tagging
During 2023 we managed to deploy four
satellite tags on reef manta rays around Wakaya
Island. Currently we know very little about the
movement ecology of mantas found here and
how well connected they are to other
populations around the country.
These tags will allow us to investigate these
movements and potential new critical habitats
in the area.
Wakaya Island
Resort
Wakaya Island Resort and Manta Project Fiji
began working together more closely in 2023,
which has been reflected in the large increase
in data collected from the area. Wakaya Island
is surrounded by a large barrier reef which
joins to the adjacent island, Mokogai. This
extensive reef system is home to a wonderful
array of marine life.
The NAI’A
Fiji
The NAI’A Fiji is the South
Pacific’s Premier Liveaboard
offering spectacular diving
throughout Fiji. Visiting Wakaya
Island regularly the NAI’A has
contirbuted significantly to manta
ID data collected around the
island duiring 2023.
The primary survey sites around the island are predominantly cleaning
stations found along the outer edge of the reef, however manta rays are
sighted foraging in areas of the lagoon during certain lunar cycles.
Number of
Survey Days
54
Manta rays were sighted
on 70% survey days
2023
247
Number of
Manta SightinGs
Average of 6.5 Manta
Rays Sighted per Survey
2023 in review
273 manta ray sightings were recorded
Surveys were conducted on 54 days between April - November
Manta rays were sighted on 70% of survey days
Average of 6.5 manta rays per survey was recorded
73 different manta rays were recorded
35 new manta rays were recorded and added to the database
4 Satellite tags were deployed

2023
2022
Sighting Distribution
Manta sightings have now been recorded from March
through to December in Laucala Bay. During the 2023
survey season, peaks in sightings were recorded in
May, July and September. With only just under two
years of consistent data collection we are looking
forward to build upon survey efforts for the 2024
season.
It is hypothesised that large amounts of fresh water
being deposited into the bay by the nearby Rewa river
cause dense zooplankton clouds to form, which the
manta rays gather to forage on.
Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Laucala Bay,
Suva
Suva
Conservation
International Fiji
Viti Levu
Laucala Bay
Key Partners
The University of
the South Pacific
The University of the South Pacific marine science
campus sits on the foreshore of Laucala Bay. This
has created a great opportunity for Manta Project
Fiji and the Univeristy to work together collecting
data in this critical ecosystem.
Conservation International Fiji and Manta Project
Fiji have collaborated on deploying technical
research equipment to better understand these
endangered rays.
Reef Manta Ray
(Mobula alfredi)
Oceanic Manta Ray
(Mobula birostris)
Project Overview
Laucala Bay sits just off of Fiji’s capital city, Suva. Laucala bay is a relatively flat
costal lagoon enclosed by a barrier reef to the South, by Suva city to the west
and the delta of Fiji’s largets river, the Rewa, in the east. Besides being adjacent
to the Rewa delta, several rivers feed into the bay shedding large amounts of
fresh water into the bay throughout the year.
After an intial oceanic manta sighting in 2018, followed by some sporadic
sightings throughout 2020, concerted manta surveys began in April 2022 to
better undertsand mobulid ray use of the site. Data is collected primarily through
drone surveys around the bay due to the size of the bay and the turbid nature of
the water.
Both species of manta ray are found in the bay, this means the bay is the only site
you can see the endangered oceanic manta ray but also one of a few sites
globally where reef manta rays and oceanic manta rays can be found foraging
together.
Drone
Surveys
193
Manta SightinGs
196
2022 2023
587
Oceanic manta sightings
Reef manta sightings
3
Drone
Surveys
583
243
Manta SightinGs
267
Oceanic manta sightings
Reef manta sightings
24
16 different manta
rays recorded
with a resighting
rate of 81%
FJ-MB-0001 was
first sighted in
late 2018 and has
been sighted 42
times since
FJ-MB-0008 is
the most sighted
manta with 61
sightings over
three years
Oceanic RESIDENTS?
FJ-MB-0001
2019 2020 2021 2022 2023 2024
2023 in review
267 manta ray sightings recorded
583 drone surveys conducted
Manta rays sighted on 46% of drone flights
8 different reef manta rays and 13 different oceanic manta rays sighted
First student-led project conducted in the bay
1 Satellite tag deployed
Individuals
FJ-MB-0020
FJ-MB-0017
FJ-MB-0016
FJ-MB-0015
FJ-MB-0014
FJ-MB-0013
FJ-MB-0012
FJ-MB-0010
FJ-MB-0009
FJ-MB-0008
FJ-MB-0007
FJ-MB-0006
FJ-MB-0005
FJ-MB-0004
FJ-MB-0002
Typically oceanic manta rays have a much lower re-sighting rate compared to reef manta rays,
hypothesised due to the difference in ecological habitat use, with oceanic manta rays
typically being associated with deeper oceanic water and a highly migratory nature.
Currently our knowledge is lacking in the homerange size of this population, we are hoping to
employ more sophisticated research methodologies in the future to better understand this
unique group of manta rays.

LAu archipelago
The sicklefin devilray
has been sighted in
Northern Lau.
Currently the only
sighting in Fiji
Image by Tom Vierus
Lau Group
Reef manta rays
make up the majority
of sightings across the
archipelago
The Lau
Group
Image by Tom Vierus
Key Partner
Conservation
International Fiji
Conservational International are supporting the
communities of Lau in creating the Lau Seascape, an
initiative which will build holistic ecosystem management
and protections.
Manta Project Fiji are collaborating with
Conservation International to deliver species
specific research and conservation goals in the region
surrounding mobula rays.
Project Overview
The Lau Group lies to the far east of the Fiji Islands, this scattered remote
archipelago is home to just 1% of Fiji’s population. Consisting of 60 islands
spread across 335,000 square kilometers, the Lau group represents Fiji’s most
remote habitats, many of which are home to incredible biodiversity and endemic
species.
Local knowledge in the region is rich, and coupled with dedicated research trips
multiple mobula species have been sighted in the region and hotspots identified.
The Lau Group is the only area in Fiji where the sicklefin devil ray (Mobula tarapacana)
has been sighted and is also home to the reef manta ray (Mobula alfredi),
and elusive oceanic manta ray (Mobula birostris).
The communities of Lau with the support of Conservation International are
working to build ocean conservation that balances protection and production of
the marine ecosystem they depend on. Manta Project Fiji is priveleged to
support this initiative by focusing on species specific research and conservation
aimed at the mobula ray family.
Our current aim in the region is to fill the large knowledge gaps that exist
surrounding mobula ray species ecology and build awareness of the species that
inhabit these waters and the pressures and threats they face.
Reef Manta Ray
(Mobula alfredi)
Vulnerable
Sighted Species
Oceanic Manta Ray
(Mobula birostris)
Endangered
Sicklefin Devil Ray
(Mobula tarapacana)
Endangered
Oceanic manta rays
have only been
recorded in the
region from tagging
data
Southern Lau has
displayed the most
manta ray sightings
Satellite tagging has revealed inter-island
migration between islands within southern Lau.
These migrations are likely to be common and
numerous amongst populations of reef manta
rays in Lau due to the oceanic nature of the
islands and distances between island groups.
We hope to deploy more satellite tags in the
coming year to investigate more about the
movement ecology across the whole
archipelago.

Feeding Sites
Zooplankton Diversity
Non-Feeding Site
Acetate Protozoa, 4%
Chaetognaths, 5%
Chaetognaths, 4%
Chaetognaths, 4%
Chaetognaths, 2%
Copepod, 75%
Lucifer sp., 8%
Copepod, 88%
Copepod, 81%
Lucifer sp., 4%
Copepod, 94%
Sagitella, 5%
Lucifer sp., 11%
Lucifer sp., 15%
Copepod, 100%
Assessing the foraging
habitat of oceanic
manta rays in laucala
bay, FIji
Suva
Viti Levu
Laucala Bay
Project Overview
Oceanic Manta Ray
(Mobula birostris)
This research project was led and designed by University of the South Pacific
undergraduate students Karalo Drekenavere and Devavrat Bishwa and focuses
on Laucala Bay, Fiji, where recurrent sightings of M.birostris raise questions
about their ecological significance and the potential impacts of anthropogenic
activities.
The investigation examined water quality parameters, fecal coliform bacteria
concentration, microplastics, and zooplankton composition within the bay at
four foraging sites and one non-foraging site. During the study a drone was used
for real-time identification of foraging manta rays and to give the boat direction
to the specific site. Once at the specified site with the manta ray foraging water
samples and parameters were taken and a plankton net deployed.
Copepods were
present at all
sampled sites,
both feeding and
non-feeding
Lucifer sp., a species of
prawn was a surprise
finding at every feeding
site. Lucifer sp. were not
present at the
non-feeding site
Chateognaths, also
known as arrow
worms were present
at all feeding sites
but absent from the
non-feeding site
Fragments, 63%
Fibres, 32%
Line, 5%
Only copepods were
present at the non-feeding
site, displaying clear
differences between the
feeding and non-feeding
site
microplastic Distribution
Feeding Sites
Microplastic fragments accounted for
63% of all microplastics collected at
feeding sites, with fibres making up
32% and line only 5%.
Water Quality Parameters:
Lucifer sp.
Key Partner
- Temperature, Dissolved Oxygen and
Salinity
- Turbidity
- Fecal Coliform Bacteria
Fragments, 13%
Fibres, 87%
Non-feeding Site
Microplastic fibres accounted for the
majority of all microplastics collected
at non-feeding sites with 87% and
fragments only accounting for 13%.
- Microplastic Composition
The University of
the South Pacific
The University of the South Pacific marine science
campus sits on the foreshore of Laucala Bay. This
has created a great opportunity for Manta Project
Fiji and the Univeristy to work together collecting
data in this critical ecosystem.
- Zooplankton Analysis and Composition
Karalo Drekenavere (right) and Devavrat Bishwa
(left) collect water samples at foraging sites in
Laucala Bay, Suva
Laucala Bay, Suva
Feeding and non-feeding
sites displayed very
different compositions of
microplastics, possibly due
to the differing
oceanographic conditions
Microplastic Fragment

Manta Conservation at Wakaya Island
During 2023 we strengthened our collaboration
with Wakaya Island Resort and conducted
more manta surveys here than ever
before. We also had the great privelge of
welcoming Dr. Mark Erdmann to the project
site where together we deployed four
satellite tags to give us the forst movement
ecology data from the area.
This documentary film by Tom Vierus
displays the project work that went on at
Wakaya Island Resort during 2023.
Tagging oceanic manta rays in Fiji
To investigate migratory routes and critical
habitat use of wide-ranging species such as
the endagered oceanic manta ray we need
to utilise various methodologies to give us
the best possible results. One of the most
effective methodologies to achieve this is by
utilising satellite telemetry.
Dive into this short video documentary by
Tom Vierus on the deployment and use of
In The Media
Oceanic Manta Rays in Fiji
Learn more about the discovery of the first
known oceanic manta aggregation site in
Fiji. This highly migratory and endangered
species has typically been a very rare
occurence in Fiji’s waters until consistent
sightings in Laucala Bay flipped the script.
A short video by Tom Vierus that was
nominated at the Wildlife Conservation
Film Festival.

Thank you
Yasawa Islands
North Kadavu Region
2023 Data Collected By:
Wakaya Island
Laucala Bay, Suva
Manta Project Fiji’s continued success would not have been possible throughout
2023 without the dedicated support of our partners and collaborators:
Rob Macfarlane
Isabella Sorovakatini
Filomena Meke
Teisa Mary Tora
Milisateki Bete
Viviana Taubera
Lily Taroi
Alisi Soderberg
Jerusha Elaisa
Isoa Mara
Wakaya Guests
Bel Chaves
Nai’a Guests
Luke Gordon
Luke Gordon
Thank you to Marc Dando for the use of all manta illustrations
We would like to specially thank the Ministry of Education and the Ministry of
Fisheries for their continued support in conducting our work across the country
Manta
T R U S T
Special thanks to Tom Vierus, Daniel Lund, Lauren Bird, Tim Stats and Beth Seargent for their support over the
years and through 2023