Reproductive biology of the dusky grouper (Epinephelus marginatus) at the southern limit of its distribution in the south-western Atlantic

Abstract

We investigated the reproductive parameters of a dusky grouper Epinephelus marginatus population at the southern limit of its distribution in the south-western Atlantic. The analysed specimens were captured between January 2008 and April 2011 at Carpinteiro Bank (CB) (32°16′S; 051°47′W), a seamount located at the 20 m isobath ~16 nautical miles from the coast. The gonads of a total of 201 individuals (184 females, 16 males and 1 individual in sexual transition) with a total length (TL, mm) between 278 and 1160 mm were analysed microscopically. Histological analyses of the gonads suggested that the species is a partial spawner with a long spawning period (between November and March) and with a reproductive peak between November and January. The average female length at first maturity (L50) was 496 (TL, mm). We also observed partially spawned ovaries and partially spawned testes, which indicated reproductive activity, and we noted the presence of hyalinised follicles. These findings reveal that CB is the southernmost portion of the south-western Atlantic in which the dusky grouper reproduces. Additionally, an inshore-offshore comparison suggested that deeper (>20 m) rocky bottoms, such as the studied seamount, constitute higher quality habitats for this species when compared with littoral (<5 m) rocky reefs.