Plenty of fish in the sea?

Overfishing and other human pressures are having a toll on the fish populations and coral reef community structure in many places around the globe, but what about Koh Tao?

A recent study by a James Cook University Master’s degree student and NHRCP intern, Fanny Couture, seeks to investigate the status of Koh Tao’s fish populations and the effects of human pressures and the implementation of Marine Protected Areas (MPAs) around the island. Her study utilizes 6 years of existing ecological data collected through the locally developed Ecological Monitoring Program plus more in depth studies that she is completing on her own.


The first write-up of her findings has been published as a special topics paper under the title of The influence of depth, benthic structure, and human coastal activities on the fish assemblages of Koh Tao Island, Thailand.  The study assessed fish biodiversity (the variety of species), the abundance of ecologically important species, and the species according to their ecological roles (herbivore, carnivore, and coralivore). Similar to the study by Margaux Hein (2013), she evaluated different sites according to the types and levels of stress at each reef location. Her preliminary results provide a baseline for which to compare future studies, but also show some interesting trends and correlations with the current populations.

To summarize some of the conclusions and most interesting points;

  • she found that the most abundant fish species around Koh Tao (of the 13 targeted genera or families)are rabbitfish (Siganidae), parrotfish (Scaridae), and Butterfly fish (Chaetodontidae).
  • There tended to be more fish in the shallow sites than the deep ones, and the density of fish in the areas deemed ‘low’ use where about 1.6 times higher than those deemed as ‘high’ use.
  • Areas with coral coverage greater than 30% had significantly more herbivores and corallivores, but actually had less predators (such as groupers and snappers)
  • In ‘high’ use sites there tends to be less carnivores, but more herbivores and corallivores
  • The diversity of fishes was very closely correlated with the diversity of benthic substrates and habitat complexity

Currently, Ms. Couture is completing another 7 weeks of research at Koh Tao with the New Heaven Reef Conservation Program. Her study will look into greater detail at the findings from her first study, but also concentrate greater on the effects of the Marine Zoning and Regulations that went into effect on Koh Tao in late 2012.