Abundance and Population Size Structure of the Crown-of-Thorns Seastar in Camiguin Island, Northern Mindanao

The abundance and population size structure of two populations of the crown-of-thorns seastar (COTS), Acanthaster sp., were investigated as part of removal activities of the seastar due to population outbreaks in two areas of Camiguin Island, Northern Mindanao. Abundances reached 75 and 160 individuals/hectare for Pasil Reef and San Roque, respectively. Mean weights and diameters were 302.64g and 340.89g, and 21.37cm and 24.09cm for Pasil and San Roque, respectively. Size frequency distribution of the diameters and weights of the seastars indicate that the populations in both areas were composed of different cohorts. The COTS population in San Roque had characteristics of a relatively more mature population compared to that in Pasil Reef. The occurrence of Crown-of-Thorns Starfish (COTS) outbreaks on opposite sides of the island of Camiguin suggests that these outbreaks are not isolated and that other outbreaks are likely happening in other areas of the island. Regular monitoring and removal of COTS might be one of the best ways to manage reefs efficiently, and these initiatives may promote better reef health.