Brian Hall, the R.V. Odyssey's science intern swims with a
magnificent manta ray! Manta Rays may attain a wing span of more than 6 meters, but for all
their tremendous size and power
they pose no threat, unlike some rays their whip like tail lacks a sting.
Photo: Genevieve Johnson
October 30, 2000
Manta rays are the largest of all rays and are the distant cousins of
sharks, both of which are cartilaginous fish. The giant black and white
manta ray may attain a wingspan of more than 6 meters. But for all of its
tremendous size and power it poses no threat, unlike some rays its whip like
tail lacks a sting, in fact the manta is as harmless as a shadow in the sea.
The only way I can describe these animals is magnificent, we watched in awe
as they materialized out of the hazy blue, flying by us on giant silent
wings. We watched them in groups of 3 and 4 gliding together with such
grandeur and elegance as to have us completely mesmerized.
The stark counter shading of the manta may act as protection against
predators such as sharks or Orcas. The dark pigmentation of the dorsal
surface, when viewed from above allows them to blend into the dark
background below. Conversely, the light ventral surface makes them difficult
to distinguish from the ambient light above.
The pectoral fins of these giants propelled them through a series of turns
and dives with emaculate grace, the purpose of which appeared to be to
assist in feeding. Gliding into our midst with cavernous mouths agape and
rows of gills flared, the long maneuverable lobes in front of the head were
being used to guide a broth of plankton into the mouth, where the krill and
small fishes could be filtered out. Just like some species of whales these
immense rays are dependent on multitudes
of the smallest animals in the sea for their survival. Feasting on the
plankton alongside the rays were several milkfish, an important fish for
human consumption here in Kiribati and much of Southest Asia.
Following the tides, these rays feed along the edges of reefs,
where the ebbing tide carries eggs and larvae into the open sea. These large
docile fish will often hang in currents allowing cleaner fish such as
wrasses to enter their enormous mouths and pick parasites from the gill
arches. This symbiotic relationship provides food for the wrasse while
protecting the manta from potentially fatal infection.
Much about these placid behemoths remains a mystery, including breeding,
birthing cycles and lifespan. Unfortunately manta rays are killed in large
numbers in many fisheries around the world. In fact one of the rays we swam
with today was trailing part of a fishing line from a lure that was firmly
embedded in its left pectoral fin.
By gaining a better understanding of these creatures, hopefully we can learn
to appreciate the significance of their place in the world's oceans.
Flying through the water with a majesty that was breathtaking, our
encounter concluded as the mantas faded from view, turning toward the open
sea, they disappeared into a blue oblivion.
Log by Genevieve Johnson
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