Vinegar injections can be used safely to control outbreaks of crown-of-thorns starfish (Acanthaster solaris) during the peak spawning season

Abstract

Concerns are mounting over the effects of COTS outbreaks, prompting the need for integrated management strategies. Although direct control methods are short-term and localized, they remain one of the few operational tools that can be easily implemented by local actors. Vinegar injections have recently emerged as highly effective method; however their impact on reproductive behavior remains untested. Here, we investigated the short-term spawning response of mature COTS to double injections of household vinegar. First, COTS abundances and reproductive status were monitored during a massive outbreak affecting New Caledonias reefs. In-situ and laboratory experiments were then conducted to determine whether injected COTS would eventually release their eggs and trigger synchronized spawning among mature individuals in close proximity. Our results indicated that injections had no significant effect on spawning behavior, even in densely populated aggregations (>4000 COTS.ha-1). In the field, starfish exhibited ripe gonads with high gamete content (up to 35% of body weight) three days after conspecifics were injected. In the laboratory, mature COTS kept with injected, decaying individuals in a confined volume did not expel their gametes after two days. This suggests that vinegar injections could be used at any time, even during peak spawning, without risking synchronized spawning in the affected areas.