As one of the longest established no-take marine reserves in the world Cousin Island provides a unique study site for the effects of protection on coral reef ecosystems. The coral reefs surrounding Cousin have undergone many changes over the past decade; they were particularly badly affected by the global coral bleaching event of 1998 which led to a reduction in live coral cover and a resultant increase in algal cover. Over the years there has been marine mapping projects and yearly monitoring to gauge abundance of fish, coral cover, invertebrates and coral recruits.
Monitoring takes place in April and October, which allows for the best diving conditions due to calm seas, the Cousin Island wardens, the Science Officer and sometimes volunteers carry out the work and the data is added to previous years to look at trends.
Results have shown that the shift from a coral reef to an algal reef hasn’t been detrimental to the fish biomass although species composition has changed.