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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