Abstract. — Otoliths were 

 used to determine the age and 

 growth of the coral trout Plectro- 

 pomus leopardus from Lizard Is- 

 land area, Northern Great Barrier 

 Reef, Australia. An alternating 

 pattern of opaque (annulus) and 

 translucent zones was visible in 

 whole and sectioned otoliths. How- 

 ever, compared to sectioned 

 otoliths, whole readings tended to 

 underestimate age of older fish. 

 Otoliths of mark-recaptured fishes 

 treated with tetracycline showed 

 that one annulus is formed per 

 year during the winter and spring. 

 The oldest individual examined 

 was 14 years of age. Schnute's 

 growth formula was used to deter- 

 mine the best model to describe 

 the growth of the coral trout. The 

 von Bertalanffy model for fork 

 length (FL) fitted the data well 

 and the resulting model was 

 L t = 52.2(1 -e -0.354U + 0.766)). 

 Line-fishing usually does not cap- 

 ture fishes smaller than 25 cm FL, 

 thereby excluding most 0+ and 1+ 

 year old fish and probably the 

 slower growing 2+ year old fish. 

 These first three years of life rep- 

 resent the period of fastest growth, 

 so, if the growth curve is fitted 

 only to the line fishing data, the 

 growth rate of the population is 

 underestimated. Multiple regres- 

 sion was used to predict age from 

 otolith weight and fish length and 

 weight. Otolith weight was the 

 best predictor of age in the linear 

 model and explained as much 

 variation in age as fish size in the 

 von Bertalanffy model. 



Age validation and estimation of 

 growth rate of the coral trout, 

 Plectropomus leopardus, 

 (Lacepede 1802) from 

 Lizard Island, Northern 

 Great Barrier Reef 



Beatrice Padovani Ferreira* 

 Garry R. Russ 



Department of Marine Biology, James Cook University of North Queensland 

 Townsville Q481 1, Australia 



*Present address: CEPENE-IBAMA. R Samuel Hardman s/n° Tamandare. 

 Pernambuco. Cep. 55578-000. Brazil 



Manuscript accepted 8 September 1993 

 Fishery Bulletin 92:46-57 (1994) 



The coral trouts of the genus Plec- 

 tropomus Oken are members of the 

 serranid subfamily Epinephelinae, 

 commonly known as groupers. 

 These fishes occur in shallow tropi- 

 cal and subtropical seas of the 

 Indo-Pacific region (Randall and 

 Hoese, 1986) where they usually 

 are at the top of food chains and 

 thus play a major role in the struc- 

 ture of coral reef communities 

 (Randall, 1987). 



Groupers typically represent an 

 important fishery resource 

 throughout the tropical and sub- 

 tropical regions of the world 

 (Ralston, 1987). On the Great Bar- 

 rier Reef, the common coral trout 

 Plectropomus leopardus (Lacepede 

 1802) is the most abundant species 

 of the genus (Randall and Hoese, 

 1986) and usually the primary tar- 

 get of recreational and commercial 

 fishermen. The Queensland com- 

 mercial line-fishing fleet takes a 

 total annual catch of about 4,000 

 metric tons (t) of reef and pelagic 

 species. The coral trout composes 

 the largest single component of this 

 catch (over 30%) with around 1200 

 t caught annually (Trainor, 1991). 

 The recreational sector of this fish- 

 ery is estimated to catch two to 

 three times the commercial catch of 

 reef fish (Craik, 1989 1 ). 



Worldwide studies on age and 

 growth of Epinephelinae indicate 

 that they are long lived, slow grow- 

 ing, and have relatively low rates of 

 natural mortality (Manooch, 1987). 

 Fishes with these characteristics are 

 susceptible to overfishing. Only by 

 obtaining validated estimates of 

 growth is it possible to determine 

 population dynamics, estimate po- 

 tential yield, monitor the responses 

 of populations to fishing pressure, 

 and properly manage the fishery. 



Some information on age, 

 growth, and longevity is available 

 for the common coral trout. On the 

 Great Barrier Reef, Goeden (1978) 

 estimated the growth rate of this 

 species at Heron Island from 

 length-frequency data. Mcpherson 

 et al. (1988), determined age and 

 growth of the common coral trout 

 in the Cairns region by counts of 

 annuli in whole otoliths. Loubens 

 (1980) estimated age and growth 

 for P. leopardus from New Cale- 

 donia from counts of annuli in bro- 

 ken and burnt otoliths. The period- 

 icity of formation of annual rings in 

 the latter two studies was verified 

 through observation of marginal 



1 Craik, G. J. S. 1989. Management of rec- 

 reational fishing in the Great Barrier Reef 

 Marine Park Tech. Memo. GBRMPA-TM- 

 23, 35p. 



46 



