Crown-of-Thorns starfish (COTS) outbreak in Sogod Bay, Southern Leyte, Philippines

Abstract

Sogod Bay is known for its high diversity and abundance of hard coral. However, this resource is under threat due to the coral predator, crown-of-thorns starfish (COTS) Acanthaster spp. The findings of 2021 COTS outbreaks in reefs belonging to territorial waters of Liloan, Libagon, San Francisco, Malitbog, and Padre Burgos, Southern Leyte, are reported here. The lowest COTS count was recorded for Padre Burgos while highest in Malitbog with 13 and 20 COTS 100 m^-2, respectively, exceeding the outbreak threshold of 0.25 COTS 100 m^-2. COTS collected from Malitbog, although highest in number, weighed lightest (251 ± 128g) while heaviest in San Francisco (621 ± 250g). The majority of COTS collected were in the juvenile stage with sizes ranging from 6-15 cm, corresponding to COTS age of 1-2 years. Regarding COTS sexes, the proportion of female COTS was higher relative to male COTS in Padre Burgos and Malitbog while lower in Libagon, Liloan, and San Francisco. A trend in the low total count of COTS regenerating arm was observed, indicative of the absence of COTS predator. Overall, the findings of this study imply that the COTS outbreak in Sogod Bay is a recurring phenomenon. Thus management efforts should be directed into areas with the over-the-outbreak threshold of COTS. The large quantities of COTS observed in Sogod Bay, Southern Leyte would further necessitate an improved management strategy, to reduce the detrimental impact of COTS outbreaks in the reef ecosystem. Periodic monitoring of COTS along Sogod Bay is recommended to reveal the extent of damage and potential clean-up efforts. Conduct of trainings to include Information, Education, and Communication (IEC) campaign to municipalities categorized under active outbreak status is also recommended. Finally, studies are warranted to look into COTS population replenishment, and outbreak drivers.