The Past, Present, and Future of Koh Tao’s Shark Bay

The Shallow Hunter


The island of Koh Tao is a slice of deliciously buttered bread. One that has had bites taken out of every side of it by the gluttonous ravages of erosion, leaving behind semi-circular bays, the teeth marks of golden sandy beaches.

Each of these are the key geographic areas used to divide the island into its different regions, each with its own unique story, and perhaps none more so than the southern most bay of them all, Shark Bay.

Here, we look to explore briefly, the difficult past, the dynamic present and the uncertain future of Shark Bay.


A Look at the Past –

This story starts as far back as we can get reliable information from, 1994, the very beginnings of New Heaven Dive School, a time when foreign presence on the island was negligible and tourism was a mere fragment of the ever growing beast it is today.


Sian Rowlands - Shark Bay

‘No boats, only two families living in the whole bay. When New Heaven moved there in 1994 we were the third family living in the bay.’ – Devrim Zahir, New Heaven Diveschool. Image taken 2003 by Sian Rowlands.

A part of the island that sees extensive boat traffic today with an average of 10-20 boats of various sizes moored up at any given time, saw boats from only 3 dive schools and a couple of small longtail boats 20 years ago. These crude moorings and small boats floated over extensive areas of pristine reef, largely dominated by branching ‘Acropora’ corals. The coral reef in turn, creating invaluable habitat for vast schools of fish including species like the king mackerel and the great barracuda, which are getting rare around the island and have all but disappeared from the bay. These species and many others have suffered similarly since then, largely due to the events of 1998.

1998 was an especially historic year for much of the world, Bill Clinton had an affair, Frank Sinatra died (and nobody had yet suffered the rise of a then 4 year old J. Beiber), and NASA found water on the moon. Meanwhile the water on earth was causing its own havoc and the world’s coral reefs suffered in the first well documented worldwide bleaching event. One of the hottest years on record causing record toppling ocean warming that effected a large portion of the world’s reefs, including those on Koh Tao.

The healthy, vibrant and diverse coral reef of Shark Bay was brought to its knees in a crippling blow, with near complete mortality of its hard coral cover leaving it largely devoid of any living hard coral in a matter of months. While most other bays and reefs around the island escaped with far less lasting damage (though none escaped unscathed), Shark Bay was hit the hardest by far.


A hugely successful coral reef growing on the metal structure - Image by Chad Scott, 2008

A hugely successful coral reef growing on the metal structure – Image by Chad Scott, 2008

Other things took longer to change, a continuation of a possible trend seen prior to the event. Changes such as reduction in numbers of large predators like barracuda and sharks was inevitable, but the current presence of large schools of rabbitfish, numbering in the hundreds, are perhaps due to the rapid colonisation of macroalgae that took place soon after the reef mortality. In the animal kingdom of the bay, the throne had arguably been held by hard coral for decades, which now lay empty, therefore paving the way with conditions perfect for a massive takeover of macro algae, which remains the dominant substrate to this day. No other part of the island looks quite like the bay does now.

To help restoration efforts for the corals in the bay, the reef conservation program created artificial structures in 2008, with a small electric current running through it resulting in a boom in hard coral growth for that small section of the bay. This subaquatic island of diversity lasted a little while before it met with accident and was unfortunately destroyed.




A Report on the Present –

The Good and the Bad – Shifting from the Dramatic, to the Scientific.

Since then the current state of the bay reflects much of what may be expected after loss of a coral reef but also much that is unexpected.

Investigating ColourShallow water corals have shown some recovery and it is once again possible to see small patches of dense Acropora branching coral, reminiscent of what it used to be. Fringe areas between the land and the central and deeper part of the bay have strong diversity but still incredibly patchy in coral coverage. Several large and old massive corals are still alive and dot the centre of the rubble fields, acting as oases of fish life in the rubble and algae. Fish diversity is incredibly high with all stages of the food web being present, from predators and meso-predators down to herbivores both large and small.

Invertebrate communities seem to be irregular, with limited numbers of herbivores such as the long-spined black sea urchin, which may be due to large amounts of predators. Detritivores such as hermit crabs and sea cucumbers remain diverse and abundant but filter feeders such as barrel sponges and giant clam species are very few in number hindering the amount of nutrients that can be removed from the bay, thereby allowing macro-algae to remain dominant.

The sombre expression of one of the oldest turtles on the island.

The number and size of turtles is by far the largest at Shark Bay, compared to every other part of the island, with daily visitations from a number of regulars and several part-timers. Thankfully, these long lived spectators of the changes of the island, have remained largely the same in terms of abundance in the past 20 years of rapid expansion.

The increasing amount of tourist activity has led to an extensive increase in the number of visitors snorkelling at Shark Bay. Many walk in from the shore and snorkel in small groups, however many arrive in large tour boats with loud music and advocating the feeding of fish, both activities causing extensive disturbance to surrounding wildlife, both in the short and long term. The bay also hosts one of the largest amount of permanent mooring lines on the island promoting sustainable mooring but also resulting in large amounts of boat traffic.

Surface ViewPerhaps the most important factor of the bay at present is the factor that draws so many tourists and keeps the entire bay in check and the name that is used to refer to the bay today. The shark population is thriving at Shark Bay, with plenty of food and space to live in, the blacktip reef shark (Carcharhinus melanopterus) dominates the food web. On a good snorkel over 20 shark sightings can be made, usually attributed to approximately 10 individuals at a time, with huge variation in distribution of sexes and sizes.

The past few years have brought some interesting things to light with regards to the shark population. It has been known for a while that in mid to late March approximately, the sharks congregate in the shallows to give birth. Footage from March 2014 revealed exactly how extensive the shark population has reached. On a very lucky morning, a very lucky snorkeller (who many months later went on to write this article) captured footage of a single school of over 30 full sized adult sharks, most of which were clearly pregnant females. Some of this footage can be seen in the second half of the video here. This highlighted the bay as potentially one of the largest nurseries for blacktip reef sharks in the Gulf of Thailand region and accentuated the conservation importance of the wildlife within the bay. In a world where shark numbers are falling faster than a free diver with a concrete bottle nursery, this indicator of growth is a pleasant fact.


The Ugly – The Threats of the Present

Shark Bay Trash Despite the successes and difficulties faced by the ecosystem of the bay to return to its former glory or retain its current presence, further threats linger and grow that endanger such a unique place. With such a large amount of group tourist activity, the bay is becoming home to large amounts of garbage, both on the seafloor, and the sea surface. Multiple underwater clean-ups have been conducted with some great success but an increase in boats will provide an everlasting flow of non-biodegradable waste. Floating plastic is especially dangerous to the bay’s resident turtles, animals which are closely linked to feeding on floating plastic waste.

Shark Bay Algae and TrashMany tourists that visit the bay have not been made aware of the damages that can be caused by walking and contacting the coral (or at least that’s the optimistic approach to understanding the issue). As a result, it is not uncommon to see people out hundreds of meters from shore standing on the surrounding coral and substrate. The shallow depth of the bay proves very inviting for those that decide floating is too much of a demanding task and therefore contribute to varying degrees to further reef degradation.

While commercial fishing around the bay is illegal and does not happen, conversely fish feeding, which is also an activity that can result in fineable penalty, is all too common with popular snorkelling boats. Fish feeding usually involves feeding bread or pineapple from the boat to attract fish for customers, leading to malnutrition and sometimes toxicity with marine species and skewing the balance within the ecosystem. This is hypothesised to increase the survival of the larvae of the crown of thorns starfish (normally eaten in their masses by fish that are now so stuffed with bread and fruit they are indistinguishable from the world’s weirdest Christmas meal). The crown of thorns starfish is an infamous celebrity species in the world of coral reefs due to its appetite for coral, read more about it here.


The Future –

With every year that goes by, another exodus of the masses visit the tiny island of Koh Tao, and this exodus grows bigger every year. This leads to further developments on the road, and therefore increasing boat traffic (let this record show that as of 2014 we still have no McDonalds on the island, but an incredible samosa man). This increase will directly affect the future of the bay and will greatly determine whether the bay flourishes or falls.

Shark Bay Sunrise

Changes in the ecosystem of the bay in the future depend strongly on 3 major factors. The individual, the community, and the global influences on the island.

Education and awareness can lead to individuals taking greater responsibility of their impacts on the bay, from coral damage to littering. To many this may seem like a minor, fanciful and ineffective solution but changes in the mindset of individuals have led to great progress on the island. Individuals that actively partake in clean-ups and spreading awareness can make the largest difference on the island.

Beach CleanupThe island community of Koh Tao is responsible for its life, on land and in the water, and several steps taken by the island will dramatically change its future. Some steps that have already been taken include the deployment of several large concrete mooring blocks in rubble areas to promote sustainable boat moorings without the need for using corals or anchors. A small area in the centre of the bay is now home to various artificial structures that support the growth of transplanted corals, which will act as a feedstock for further coral growth in the years to come. Yet there is much more the community can do such as enforcement of many of the rules that help protect the bay and reduce the amount of garbage reaching the bay from terrestrial sources.

The final factor influencing the island is the global response to the inevitable topic that remains taboo in so many parts of the world. Climate change and the global warming it causes is leading to ever more frequent spikes in ocean temperature leading to degradation of the reefs worldwide. Decrease in this frequency would allow the reef the stability and time it needs to recover to once again support the unique ecosystem it once did, and support the incredible diversity it does today. This can only be changed by a combined effort from the global community, which as always, comes down to the individual.

The history of Shark Bay has shown how delicate a coral reef can be, but it has also shown the resilience of an entire ecosystem. It is also beginning to show us the potential for recovery of a coral reef, if given the opportunity to do so. The creatures that inhabit this bay are as unique as the island is itself, and therefore Shark Bay is a treasure worth protecting.


It's Always Feeding Time