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

ABSTRACT: Concerns are mounting over the effects of crown-of-thorns starfish (COTS) (Acanthasteridae) 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 locals. Vinegar injections have recently emerged as a 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 Caledonia’s reefs. In situ and laboratory experiments were then conducted to determine whether injected COTS would 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) 3 d after conspecifics were injected. In the laboratory, mature COTS that were held with injected, decaying individuals in a confined volume did not expel their gametes after 2 d. This suggests that vinegar injections could be used at any time, even during peak spawning, without risking synchronized spawning in the affected areas.