Yasawa Annual Report 2022

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5. Population DemographicsAs of 31st December 2022, the total number of different reef manta rays which have been recordedat the Manta Channel since the project was first created is 135 individuals (10 individuals wererecorded before 2012), with the total number of reef manta rays recorded at the site standing at140 individuals (5 mantas were first recorded first elsewhere).Figure 10 - Discovery curve of the Yasawa Island population16
When looking at the discovery curve (Figure 10) we can see that every year a consistent numberof new manta rays are recorded, except for 2017-2019 when no new manta rays were recorded.With the curve still on an upward trajectory it could indicate that this population of manta rays isboth healthy and larger in size than what we have recorded and that the manta rays which make upthe majority of sightings show high site fidelity to the Manta Channel.5.1. Sex DemographicsSince 2012, 140 individual reef manta rays (71 males, 68 females and 1 individual of unknown gender)have been identified at the Manta Channel comprising of 31 % of the whole Fiji reef manta raypopulation. The split of almost 50/50 between males and females is typical of a site predominantlyuse for foraging as the channel is (Figure 11).Figure 11 - Sex demographics of the Yasawa Island popultion5.2. Maturation DemographicsMaturation status in manta rays can be determined by the presence of mating scars or visible pregnanciesin females, or by the enlargement and calcification of claspers in males. If visual featuresare not apparent, then the size and historical sighting records of individuals can be consideredto help estimate maturation status. If an individual was estimated or measured to be at, or largerthan, 320cm disc width in females, or 270cm disc width for males, they were considered adults.Figure 12 - Lifestage demographics of the Yasawa Island population17
Page 1 and 2: The Yasawa IslandsAnnual Report2022
Page 3 and 4: Executive SummaryThis report presen
Page 5 and 6: Manta Project Fiji (MPF) currently
Page 7 and 8: 1.1. The Yasawa IslandsThe Yasawa I
Page 9 and 10: 3.2. 2020 & 2021The 2020 & 2021 sur
Page 11 and 12: 4.1. Oceanic manta ray sighting tre
Page 13 and 14: Consistent with the increase in sig
Page 15: During the 2022 season the highest
Page 19 and 20: 5.4. New IndividualsDuring the 2022
Page 21 and 22: 6. Residency & MigrationThe populat
Page 23 and 24: Figure 18 - Dot plot showing manta
Page 25 and 26: RabiIslandNamena IslandWakayaIsland
Page 27 and 28: The gestation period of manta rays
Page 29 and 30: 9. Environmental VariablesManta ray
Page 31 and 32: 10. TourismTourism accounts for app
Page 33 and 34: Figure 26 - Bubble plot showing ann
Page 35 and 36: Little is known about other critica
Page 37 and 38: MPF is dedicated to assist local co
Page 39: The report was compiled by :Luke Go

Yasawa Annual Report 2022

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