Couture, Fanny. 2013. The influence of depth, benthic structure, and human coastal activities on the fish assemblages of Koh Tao Island, Thailand. Special Topics paper, James Cook University, Australia.
Fish communities are structured by both the natural and anthropogenic processes that they are exposed to. With escalating worldwide declines in fish stocks, there is a growing awareness of the need to understand the ecological processes affecting the structure and productivity of fish communities. This study, aimed to evaluate the influence of depth, benthic structure, and anthropogenic impacts (i.e. boat traffic, fishing, snorkeling and diving, sedimentation and waste water run‐off), on fish assemblages of the Koh Tao Island, Thailand. The most numerically abundant fish families of our study were Parrotfish (Siganidae), Rabbitfish (Siganidae), and Butterflyfish (Chaetodontidae), with mean densities of 0.45, 0.5, and 0.55 individuals per 100m2 respectively. A positive relationship was detected between habitat heterogeneity and fish diversity, but also between hard coral cover and the abundance of Butterflyfish and Parrotfish. Reefs impacted by sedimentation supported lower densities of corallivores and herbivores. Even though large individuals were more generally abundant in sites with low diving and snorkelling pressure; diving, snorkelling, and fishing activities did not appear to have a major influence on the spatial distribution of fish families and trophic groups. Our study also showed that the implementation of a fish sanctuary zone (no‐take marine reserve) in 1996 around the west part of Koh Tao did not influence fish abundance. This finding was likely due to poor compliance (poaching) within the reserve and highlights the need to improve surveillance, research, and education about the conservation and fishery benefits of maintaining an effective reserve network. Further research is required to examine the effects of habitat quality, depth, disturbances, human usage, and no‐take reserve protection on the structure and productivity of fish communities at Koh Tao Island.