Individuals of Pomacentrus mollucensis were collected from the lagoon of John Brewer Reef on the central Great Barrier Reef between March 1988 and February 1989 and their otoliths examined to assess determination of age-specific parameters.
Fish were collected on 4 occasions (16 March 1988, 3 September 1988, 3-4 November 1988, 26-27 February 1989) and injected with tetracycline. Recaptured fish (September 1988, February 1989) were examined to determine any increment in the otolith structure that had formed since treatment with tetracycline.
Otoliths were measured along various axes from 182 specimens. Prior to dissection, fish were weighed (preserved weight in mg) and measured (standard length in mm). All analyses were done on the sagittae, the largest pair of otoliths. Sagittae were weighed (to 10-2 mg) and measured along 3 axes (OL1 = total length; OL2 = distance from the base of the dense, opaque region to the tip of the otolith; OB = otolith breadth). All measurements were made as close as possible through the otolith core.
Aging work was based on the analysis of tranverse sections of 124 otoliths. One sagitta from each fish was ground and polished to produce a thin section (50-100 µm thick) incorporating the central core or as close as was possible. Sections were measured from the central core to each of 4 peripheral points (L1 = ventral apex; L2 = the dorsal apex; L3 = the ventral and L4 = dorsal sides of the sulcus).
Von Bertalanffy growth curves and age structures were derived for 3 representative samples using FISHPARM.
