Does copepods influence dusky grouper (<i>Epinephelus marginatus</i>) early development?

• Main Authors: Monica Mateus, Paulo Gavaia, Maria Emilia Cunha
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2014-06-01
• Series: Frontiers in Marine Science
• Subjects: fish larvae; Controlled mesocosm; Acartia grani; digestive enzymes; skeletal malformation
• Online Access: http://journal.frontiersin.org/Journal/10.3389/conf.fmars.2014.02.00024/full

Good knowledge on the development of early life stages is essential for successful conservation programs of threatened fish species. Diet and rearing system affects early life survival and juvenile quality. Copepods are the natural food of fish larvae in the wild possessing high nutritional value, when compared with live feeds used in aquaculture (rotifers and artemia), and a wide range of size classes. Rearing systems with low water column disturbance and low larval densities enhanced the survival of fragile fish larvae. The aim of this work is to evaluate the effect of the introduction of copepods in the diet of early dusky grouper larvae reared in controlled mesocosm systems using larval development and juvenile quality as indicators. Two feeding protocols were tested, one composed only by rotifers (<i>Brachionus plicatilis</i>), brine shrimp (<i>Artemia</i> spp.) and dry feed and the other supplemented with copepods (<i>Paracartia grani</i>) from mouth opening (2 day after hatching - DAH) to 8 DAH. Feeding behavior, growth, survival, skeletal malformations and digestive enzymes activity was assessed at different developmental stages. The addition of copepods to the early larvae diet of dusky grouper resulted in faster development and higher survival rates. Larvae fed with copepods improved their development. At 20 DAH all larvae reared at the mesocosm with copedods were already at the stage of post-flexion while in the system without copepods this stage was attained later. At 25 DAH only 64% of the larvae were in post flexion in the mesoscosm without copepods. At 30 DAH larvae supplemented with copepods attained an acidic digestion (high specific activity of pepsin) earlier than at the system without copepods. In this last system alkaline digestion (trypsin specific activity), characteristic of early larval stages, was significantly higher reinforcing the faster development of larvae fed with copepods. In both systems the incidence of skeletal malformations was low.