Yasawa Annual Report 2022

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Figure 22 - Dot plot showing the causes of the different injuries recorded on individuals at the Manta Channel, Yasawa Islands, FijiFigure 23 - Plot to show the origin of the different injuries recorded on both male and female manta rays at the Manta Channel, Yasawa Islands, Fiji28
9. Environmental VariablesManta ray sightings at the Manta Channel are seasonal, increasing during the cooler months fromApril through to October and dying off in the warmer summer months from November-March(Figure 16). Manta rays are not sighted at all during peak summer months (December - February)at the Manta Channel.The Manta Channel is primarily a foraging site for the manta rays that visit (Figure 9), which meansthat environmental conditions directly affecting zooplankton abundance directly affect the numberof manta rays that utilise the habitat. Understanding the environmental conditions that leadto high plankton diversity will allow us to better understand the drivers behind manta ray movementsin the region.It is well documented in other locations that increases in chlorophyll-a concentration and primaryproductivity coincides with peak manta season (Dewar et al., 2008; Anderson et al., 2011). In theMaldives, for example, it has been documented that predominant wind direction and chlorophyll-aconcentration heavily affects monthly manta ray sightings at down current sites (Harris, 2020).We believe similar dynamics are at play at the Manta Channel due to the increase in sightingsthrough the SE trade wind season.The vast majority of manta sightings are recorded at the channel when the wind is blowing froman easterly direction, including SE and NE (Figure 24). These winds are characteristic for the timeof year when manta ray sightings peak at the Manta Channel. The cooler water temperature alsolikely aids plankton density as it appears higher densities are associated with water cooler than 28degrees celsius (Figure 25).It is likely that due to the geographical position of the channel, nutrient rich water is blown withthe winds into the channel and surrounding waters, creating favourable environments for planktondensity. This plankton is then funnelled through the narrow channel, creating a perfect foragingopportunity for manta rays.29
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 and 16: During the 2022 season the highest
Page 17 and 18: When looking at the discovery curve
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: The gestation period of manta rays
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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