Yasawa Annual Report 2022

The Yasawa Island population when split by sex into different life stages can be seen in Figure 12.
52 % (n = 37) of males are mature compared to only 31 % (n = 21) of females being mature, both
male and females are comprised of 29% sub-adults (n = 20). Juvenile males only make up 14 % (n =
10) of the male population, however, juvenile females make up 38 % (n = 26) of all females (Figure
12).
5.3. Color Morph demographics
The reef manta ray population in The Fiji Islands includes individuals of both chevron colour morph
and the less common melanistic (black) colour morph. Melanism, a recessive genetic trait, leading
to an over-production of the skin pigment melanin, causing individuals expressing the gene to be
completely black in colouration apart from a ventral area of white between the gills which varies in
shape and size amongst individuals.
Amongst the global reef manta ray population this condition is rare, the Maldives for example,
which is home to the largest reef manta ray population in the world (n = >5000 individuals) does
not have any melanistic individuals currently in the database, however in certain areas of the Pacific
Ocean melanism is much more common.
Figure 13 -Color Morph demographics of the Yasawa Island population
The Yasawa Island population currently displays the highest proportion of melanistic manta rays
within the country, 48 % of individuals (n = 67) are melanistic morphs and 52 % of individuals (n =
73) are chevron morphs (Figure 13). This could tentatively indicate a limited genetic connection to
the populations in other parts of the country which have a lower melanistic proportion.
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