Response of herbivorous fishes to crown-of-thorns starfish Acanthaster planci outbreaks. Age, growth, mortality and maturity indices of Acanth urus nigro f uscus Anthony M. ~a r t ' r~v * , ABSTRACT. Age, growth, mortality and maturity indices of Acanthurus nlgrofuscus were examined as part of a larger study investigating a long-term response of herbivorous reef fish to crown-of-thorns starfish (COTS) outbreaks The principal objective was to compare otolith growth, mean age and slze, growth,

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... tality, size-at-age, size-at-maturity, and age-at-maturity of A. n~grofuscus between 2 COTS affected (Yankee, Dip) and 2 non-affected I-eefs (Bowl, Coil). All reefs were exposed, outer shelf reefs in the central section of the Gieat Bairiei Reef Additionally, these demographic parameters were also established at 2 mid-shcslf reefs [Grub, Centipede) This species is relatively long-lived with the oldest specimen aged at 25 yr Mean age at each reef ranged from 5 4 to 9 5 yr, while average slze ranged from 16 to 12 cm Mean size and size-at-age was significantly larger on COTS impacted reefs, evidence which supports the hypothesis of a response to increased food resources There were also significant differences in size-at-age between ieefs withln a COTS status No differences in moitality between reefs was detected while age-at-matunty was 2 yr at all reefs Size-at-maturity was 13 to 14 cm on midshelf reefs Grub and Yankee, in contrast to 10 or 11 cm on outer shelf reefs Yankee Bowl, Dlp and Coil Importantly, age validation provlded 5 response vanables (otolith growth, mean a g e s o m a t~c growth rates, size-at-age, age-at-maturity) which were used to examine the effects of ecological disturbance on the population biology of reef fish This further ~llustrates the usefulness of a g e validation studies for coral reef fish KEY WORDS. Acanthasterplanci Acanthurus nigrofuscus -A g e -Growth . Mortality. Response vanables 'Correspond~ng address. ICLARM Coastal Aquaculture Centre,