Feeding preferences of the dusky grouper (Epinephelus marginatus, Lowe 1834) larvae reared in semi-intensive conditions: A contribution addressing the domestication of this species

Despite research efforts addressing artificial propagation, dusky grouper aquaculture still relies on experimental trials owing to the low survival rates of larvae and juveniles, thus rendering mass rearing difficult to attain. Although some authors suggested that the preys offered to the early larval stages represent the major problem facing the rearing of all grouper species, very little information is available in literature on larval development and the behaviour of dusky grouper. The objective of this study was to investigate the trophic preferences of larval stages of the dusky grouper by rearing using a semi-intensive technology. Larvae were reared in pilot scale mesocosms (60 m3) from 3 to 35 days post hatching. The rearing system was supplied with wild zooplankton collected in a natural coastal lagoon in order to augment the chances of satisfying the larvae's feeding requirements; the feeding preferences were analyzed during ontogenesis. The relationship between mouth gape and dimensions of preys, considered as 3-D objects, was investigated to identify possible critical factor. The results of this study suggested a sequence of suitable food items from the beginning of exogenous feeding until day 35 post hatching. In particular, dusky grouper larvae actively select copepod nauplii in the size range between 2 and 12 mm in TL, and Artemia salina nauplii for TL larger than 9 mm. The rearing approach applied seemed to be promising. Indeed, while previous rearing trials of dusky grouper failed within ten days or finished at 30 days post hatching with a lower percent of survivors, this paper reports the best survival rate reported for this species (10%±7.0 survivors at 35 days post hatching). Finally, mouth width was observed to be the limiting factor in the selection of prey, while the smallest prey size plays a critical role in determining ingestion. Our results contribute to clarifying some aspects of the larval ecology of this species, furnishing some suggestions for its cultivation.