ESR SPECIAL PrePrint (2008) - Abstract

ABSTRACT: Previous studies have developed size-at-age curves for goliath grouper; however, these data were based on relatively few immature individuals, and age estimation was otolith-based, requiring sacrifice of this federally protected fish. In the present study, scales, dorsal fin-rays and dorsal spines were explored as potential non-lethal ageing alternatives for juvenile goliath grouper. Annulus marks were validated using marked-recaptured fish, oxytetracycline injections, and edge analysis. A subset of fish was sacrificed to compare the scale, spine and ray ages to otolith ages. A 40% recapture rate provided a useful time series of in situ age and growth data. Scale and ray ages were unreliable, but dorsal spines demonstrated agreement with corresponding otolith ages. Annuli were best represented by translucent bands in spines, as opposed to opaque bands in otoliths. Spines were positively validated for periodicity of annulus formation. Annuli formed at different times of the year in spines than in otoliths. By correcting for this difference using a biological age method, better agreement between otolith and spine age was achieved. Dorsal spines are recommended as the primary method for ageing goliath grouper between the ages of 0 and 6 yr. This study illustrates the use of a non-lethal method to determine age of a protected species.

KEY WORDS: Serranidae · Epinephelus itajara · Goliath grouper · Jewfish · Protected species · Age and growth · Dorsal spines · Dorsal fin-rays · Otoliths · Age validation · Non-lethal ageing