Age and growth of dusky grouper (Epinephelus marginatus) (Perciformes: Epinephelidae) in the southwestern Atlantic, with a size comparison of offshore and littoral habitats

Abstract

We examined the age and growth of dusky grouper (Epinephelus marginatus) at offshore Carpinteiro Bank (32°16′S; 52°47′W) in the southwestern Atlantic through the analysis of growth increments in otoliths. We also examined the hypothesis that this offshore habitat represents a superior site for fish growth compared with inshore habitats. Samples consisted of 211 groupers captured by small-scale fisheries between 2008 and 2011 and with total lengths ranging from 150 to 1160 mm. Otolith growth increments were deposited once per year, and opaque bands formed mostly during the summer, as determined through marginal increment analysis. Ages ranged from 1 to 40 years, and most fish were aged to be between 2 and 8 years (global mean: 7.4 years, standard deviation 6.9). Von Bertalanffy growth parameters for pooled sexes were L∞=900.9 mm, K=0.129 and t0=−1.45. Fish from the offshore habitat were generally older and their mean sizes were significantly larger at ages 3, 4, 5, and 6 than those of fish from the inshore habitat. Our findings highlight the importance of Carpinteiro Bank as an important growth habitat for dusky groupers in the south-western Atlantic and indicate that fishery management measures should be implemented to ensure the maintenance of this endangered species in this off-shore bank in the future.