Red Tide: A tragedy waiting to happen to humans by feeding the whale sharks
Red Tide: A
tragedy waiting to happen to humans by feeding the whale sharks*
In Oslob,
Cebu, Philippines, the sun rises where the sky and the sea meet. Meanwhile, along
with the sun, tourists and fisherfolks-turned-tourist-boatmen rise early too to
have their meet-and-greet with the whale sharks and have underwater selfies
with them. In this otherwise quiet town, the whale sharks, locally called butanding, pass by every morning, and
their arrival causes the chaos mix of business opportunity and holiday
pleasure.
The typical
day starts with tourists lining up for registration and waiting for the short
orientation on the do’s and don’ts like no touching of the whale shark as it is
locally penalized and no use of sunblock. Then this is followed by the business
pitch of unlimited taking of photos under the sea for the group. On top of the
rent for the underwater camera, one can pay for the picture only or bring home
everything in the memory card. The bragging right of having one’s photo taken
with the butanding is then taken
home. Welcome to the “whale shark selfie
capital of the world.”
Happy tourist,
employed fisherfolks. Everybody is happy by noon when tourism calls it a day.
But the tale does not end there. This is just the human take on the day’s pie.
Whale sharks
are actually sharks that share some characteristics of whales, starting with
how big it can get. They are filter feeders and feeds almost exclusively on
plankton and small fishes. Whale sharks are migratory animals. Whale sharks
move short distances of approximately 20 km in search of food and have seasonal
migration too. They also go deep water migration in search for food and balance
their temperature.
Researchers first
sighted whale sharks in Donsol, Sorsogon and Brgy. Tan-awan, Oslob, Cebu and
considered them as part of the migration areas of the whale sharks.
Whale sharks
passing by the shallow waters of Oslob is said to be a man-made stop-over for
the whale sharks. What happens in Oslob is that the boatmen lure the whale
sharks to come by the shallow waters by feeding them with shrimps. This is
where the real concern begins.
Whale sharks,
being migratory animals, rarely reside in one area for more than 30 days. The
whale sharks in Oslob spend on average 44.9 days in the area. A maximum residency of
572 days for one individual was recorded. The effects of this change in the
migratory activity of the whale sharks are still a subject of research for the
marine biologists, but all these types of movements are surely affected by
tourism in Oslob.
Researchers
say that the normal habit of whale sharks is to constantly move from shallow
waters to deep waters but in Oslob, they spend half a day in shallow waters,
then move for the other half a day to deep waters and this change in movement
habits is an issue itself, causing a rise in the stress levels. Staying too
long at the surface will heat the whale sharks and increase their stress levels
and stress can affect survival because it changes the way the whale sharks use
their daily energy. Changes in physiology, growth, immune system levels,
general health, and reproduction are associated with elevated levels of stress
in the whale sharks.
What
is Filter Feeding?
Whale sharks
have a mouth that can be 1.5 meters wide filled with 300 to 350 rows of tiny
teeth and 20 filter pads which it uses to filter feed. Whale sharks' mouths are
located at the front of the head rather than on the underside of the head.
The whale
shark is a filter feeder and it feeds
on plankton including copepods, krill, fish eggs, and small nektonic life like small
squid or fish as well as on clouds of eggs during
mass spawning of fish and corals.
Filter feeding
is either by ram filtration or active
suction. In ram filtration, the animal opens its mouth and swims forward,
pushing water and food into the mouth while in active suction feeding, the
animal opens and closes its mouth, sucking in volumes of water that are then
expelled through the gills.
In both cases,
the filter pads serve to separate food from water. Food separation in whale
sharks is by cross-flow
filtration
where the water travels nearly parallel to the filter pad surface, not
perpendicularly through it, before passing to the outside, while denser food
particles continue to the back of the throat. This is an extremely efficient
filtration method that minimizes fouling of the filter pad surface. Whale
sharks have been observed "coughing", presumably to clear a build-up
of particles from the filter pads. Whale sharks migrate to feed and possibly to
breed.
The whale shark is an active
feeder, targeting concentrations of plankton or fish. It is able to ram filter
feed or can gulp in a stationary position. This is in contrast to the passive
feeding basking shark, which does not pump water. Instead, it swims to force
water across its gills.
A juvenile whale shark is
estimated to eat 21 kilos of plankton per day.
What
are Plankton?
Plankton
are the diverse collection of organisms that live in large bodies of water and are
unable to swim against a current. Plankton are primarily divided into broad
functional groups such as phytoplankton, zooplankton, bacterioplankton,
mycoplankton, and mixotrophs.
Phytoplankton are autotrophic prokaryotic or eukaryotic algae that live near the water surface
where there is sufficient light to support photosynthesis and among the
more important groups are the diatoms, cyanobacteria, dinoflagellates and coccolithophores.
What
is Red Tide?
Though
we cannot see them, there are innumerable microscopic algae drifting through
the ocean and they come in many shapes and sizes, like the diatoms which are
geometrically beautiful, and the dinoflagellates which swim in a distinctive
whirling pattern.
These
tiny algae fuel the food web by getting light energy from the sun, but when
supplied with excess nutrients, they can multiply uncontrollably and become the
unwanted mass we commonly call Red Tide which
is scientifically called harmful algal
blooms or HABs. But not all red tides are red as there can be brown, and
not all of them even become dense enough to color the water. This massive
growth of algae can become harmful to both the environment and humans.
Whale
Shark as ecosystem engineer
The whale
sharks tourism in Oslob has definitely improved the local economy and reduced
the pressures on fishing among fishermen since they turned into boatmen and
their wives became cooks in a carinderia
or eatery and peddlers of souvenir items.
However, having
understood the feeding pattern of whale sharks, we just can’t let the boatmen
lure them with shrimps and turn them into pets who do not know how to hunt for
their own food.
Whale sharks
are wildlife animals and their feeding skill is necessary for their survival.
Also, what they feed on is necessary to our own survival as humans. If whale
sharks start to rely on what is given to them, they will not anymore feed on
the plankton, among them the algae that carry the dinoflagellates and diatoms
that cause red tide when they multiply out of control.
In a poem I made in 2016, I
expressed this concern and in the poem, it was the whale shark which realizes
the need to feed on its own, and if it really loves humans, it has to go its
own way, the nature’s way.
A Whale
Shark's Tale
I did not know
that you were
aching
to see my
spotted Samson-like muscles
in your waking
hours.
Each day, I
pass by your shore
and I do not
mind you
because I am
on a mission.
I am no Samson
of your circus;
I was born to
filter the waters
that is the
source of your life.
I am nature's
Ecosystem Engineer.
Yet you simply
admire my monstrosity,
and perhaps,
you are only attracted
by the danger
attached to my last name.
Do not be
fooled.
My bloodline
is sure made to fiercely bite
while I was
created to humbly clear your waters.
You lure me
with your tiny reddish catch everyday
and I tend to
heed your altogether generous and alluring call.
You captivate
me, I must admit.
But I have to
quickly shake myself
from this
madness:
If I continue
being with you this way,
I will let
your waters get red.
And I will
lose you.
Slowly.
Surely.
But hey, in the real world, humans
think for the whale sharks and not the other way around.
Readings for this Paper:
https://en.wikipedia.org › wiki › Whale_shark
Specks, An Anthology of poems by Gerlie M. Uy, page 32.
*This is the paper I submitted for the Asian Scientist Writing Prize with recent corrections made before posting it on the blog. See my introductory post to this paper here.
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