Environmental impact monitoring of household vinegar-injections to cull crown-of-thorns starfish, Acanthaster spp.

Large-scale population outbreaks of the crown-of-thorns starfish (COTS, Acanthaster spp.) have occurred in every nation with substantial coral reefs in the Indo-Pacific during the past few decades. While a multitude of control efforts have been trialed to combat the outbreaks, an efficient solution has remained elusive. Recent developments have however introduced single-shot injection methods using bovine derivatives (bile salts) and household products (vinegar) that have proven effective at culling COTS. In this study we use a Multiple-Before-After-Control-Impact (MBACI) experimental design to conduct an assessment of the environmental impact of using household vinegar as a chemical for culling COTS. During our six-week assessment we found no changes in coral cover or coral disease. Furthermore, while video recordings documented a number of fish species consuming decaying COTS, we found no evidence of changes in fish abundance or the presence of fish disease, despite densities of injected COTS far exceeding those recorded during natural outbreaks. The efficiency of scavenging fish ensured that few traces of decaying COTS were visible 72 h post-injection. The lack of any observed environmental impact supports our conclusion that vinegar is a low-risk chemical for use in COTS control. Because vinegar is highly accessible, low in cost, and effective at killing COTS without harm to non-target organisms, it has the potential to become a powerful new tool to defend the reef against COTS outbreaks.