Coral reefs provide habitats to around one quarter of all known marine species, supporting a diverse range of invertebrates and fish. Every organism that lives in a coral reef ecosystem has a specific role to play. Collectively, these roles are important for maintaining a balanced and healthy ecosystem where biodiversity can thrive.

Diving Koh Tao Thailand
Across the globe, fish living on coral reefs have become increasingly exposed to threats including overfishing, pollution and habitat loss from climate change and ocean acidification. Several local factors may also cause significant stress to reef fish communities including damage to their coral habitats from divers, snorkelers or boat anchors.
Certain fish species may be strongly influenced by a specific disturbance or change that occurs within an ecosystem (e.g. algal blooms, overfishing of species that predate on them etc.), responding with either a significant growth or reduction in their population size. These species may highlight specific events that have occurred in an environment, and are therefore referred to as indicator species. Monitoring the relative abundance of these species over time can help identify threats that are present to a particular reef.

The complex structures that corals build provide shelter and protection to several reef fish species. Significant damage caused to the reef often has serious consequences on the ability of fish species to survive, often resulting in a reduction in reef fish abundance and diversity, and sometimes even the loss of an entire species in a particular area. Biodiversity of reef fish is therefore often a good measure of reef health and can be used to assess how the health of a reef is changing over time.
Coral Habitat Koh Tao
Reef fish monitoring programme

Around 4,000 species of fish are found living on coral reefs. These fish are essential for top down control of other reef organisms and play a significant role in the structuring of reef communities. Some fish feed on algae and prevent it from overgrowing the entire reef, others control populations of invertebrates or smaller reef fish. Many reef fish predators have a varied diet that includes a collection of different prey species. If the population size of any one of their prey starts to become very large, predation of this species occurs more frequently. This often prevents any one prey from outcompeting all other species of similar ecology, and allows multiple species to coexist in the same environment. Reef fish predators therefore play an extremely important role in maintaining biodiversity of organisms that occupy a similar ecological niche (role) on the reef.

The reef fish monitoring programme established by the Roctopus ecoTrust aims to provide information on the health status of reefs around Koh Tao. This programme also aims to identify specific threats that local reefs are subject to, and the effect these are having on local reef fish communities. Several sites that are representative of typical reef ecosystems around Koh Tao are included for monitoring each month. At each site, data is collected on the abundance and biodiversity of reef fish.

Many fish included in this program are important indicator species. Trends in the relative abundance of these fish are also analysed in order to better understand specific disturbance or environmental stressors that exist in certain areas. Results from this monitoring program may provide essential information on specific areas that require conservation efforts and what the most effective management plans should include for these affected areas.
Fish Research Koh Tao

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