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- Larval and juvenile development of dusky grouper Epinephelus marginatus reared in mesocosmsPublication . Cunha, M. E.; Re, P.; Quental-Ferreira, H.; Gavaia, Paulo J.; Pousão-Ferreira, P.The larval development of the dusky grouper Epinephelus marginatus up to the benthic juvenile stage is described in detail to establish a reference for their larval identification. Development is described in terms of ontogenetic changes in morphology, growth, pigmentation, fin structure and skeletal structure. Larvae were reared in mesocosms at a mean temperature of 24·3◦ C, salinity of 36·5, dissolved oxygen of 6·4mg l−1 and pH of 8·2. Newly hatched larvae had an estimated total length (LT) of 2·3 mm. On the second day post hatching the yolk was almost fully absorbed with traces of the oil globule still present, the eyes were already pigmented and mouth and gut functional. At this stage the cranial skeletal elements for feeding and breathing (mouth and gills) and the pectoral-fin support were already present. About 50% of the observed larvae had food in their guts. Pigmentation was very characteristic, consisting of two large chromatophores visible on the edge of the primordial fin, close to the midpoint of the post-anal region of the body and over the midgut and hindgut and post-anal portion of the body. At 2·9mm LT the emergence of the second dorsal-fin spine, characteristic of the Epinephilinae, was clearly visible. The pre-flexion stage started in larva of 3·2mm LT. At 5·5mm LT the larvae possessed posterior preopercular angle spines, and the dorsal and pelvic spines presented serrated edges and were pigmented. The water surface-tension-related death of the yolk sac and pre-flexion larvae described in the rearing of several other grouper species did not occur during E. marginatus culture. Notochord flexion, with initial ossification of the caudal-fin supporting elements, started at 6·6mm LT. At this stage the major melanophores, preopercular, dorsal and pelvic spines and mandibular teeth were already present. Transformation of larvae into juveniles occurred when larvae averaged 13·8mm LT. Juveniles with a mean LT of 20·1mm started to settle and most of them were benthic with a mean LT of 26·8 mm.
- Rearing fish larvae for extensive and semi-intensive aquaculture - the “natural” mesocosms systemPublication . Cunha, M. E.; Quental-Ferreira, H.; Boglione, C.; Palamara, E.; Gavaia, Paulo J.; Pousão-Ferreira, P.Non-intensive aquaculture systems are rapidly generating interest due to increased awareness of consumers about environmental issues, including those associated with coastal areas; eutrophication as a result of intensive aquaculture production is seen as a problem, there is concern about animal welfare issues in fish rearing, and food safety is of course a major concern.
- Fish larvae quality descriptors: an appraisal of methods for red porgy Pagrus pagrus and grouper Epinephelus marginatus produced under different rearing conditionsPublication . Andrade, Carlos A. P.; Nogueira, N.; Silva, Paula; Cordeiro, Nereida; Cunha, M. E.; Pousão-Ferreira, P.; Ribeira, Laura; Bandarra, N.; Gavaia, Paulo J.Quality control in fish hatcheries is of paramount importance to achieve the desired characteristics of larvae and fry, either for the market or release to the wild. Quality programmes are applied in a day to day basis having direct implications for production management and final costs of product. Most common criteria used for larval quality assessment are morphometrics, condition factor, histometrical indices, lipid analysis, nucleic acid ratios, enzyme activity and stress tests.
- Skeletal quality in Senegalese sole: characterization of fish resulting from environmental and nutritional trialsPublication . Gavaia, Paulo J.; Dionísio, Gisela; Cardeira Da Silva, João; Cunha, M. E.; Pousão-Ferreira, P.; Conceição, L. E. C.; Cancela, LeonorThe Senegalese sole (Solea senegalensis) is characteristic from southern Europe and Mediterranean. It has recently been adapted for aquaculture production since it is well accepted by consumers and reaches high commercial values. After the initial description of the ontogenic events of skeletogenesis, systematic evaluation of the incidence of skeletal malformations by several groups revealed high levels of skeletal deformities reaching up to 90% of the population.
- Rearing larvae of dusky grouper, Epinephelus marginatus (Lowe, 1834), (Pisces: Serranidae) in a semi-extensive mesocosm | La cría de larvas de mero, Epinephelus marginatus (Lowe, 1834), (Pisces: Serranidae), en un mesocosmos de tecnología semiextensivaPublication . Cunha, M. E.; Quental, H.; Barradas, Ana; Pousão-Ferreira, P.; Cabrita, Elsa; Engrola, S.One of the major obstacles to propagating dusky grouper, Epinephelus marginatus, is the difficulty of rearing the early larvae. We have successfully raised dusky grouper larvae in mesocosms using a mixed diet of endogenous plankton grown in the rearing tank and an exogenous supply of Brachionus plicatilis and Artemia sp. Newly hatched larvae at an initial density of 1.3 ind.l-1 were stocked in partially shaded 3 m3 circular outdoor tanks during the summers of 2007 and 2008. Before introducing newly hatched larvae, the water was left for six days to promote plankton growth. Larval growth occurred at two different rates: i) a faster rate from first feeding to the beginning of metamorphosis, and ii) a slower rate at transformation. Survival at the beginning of metamorphosis was less than 10% (33 DPH) in 2007 and between 25 and 50% (25 DPH) in 2008. High mortalities were observed during larval transformation. The estimated minimum food requirement per grouper larvae increased more than 300% from the beginning of the notochord flexion to the beginning of metamorphosis. To meet such a high feeding requirement the number of larger prey organisms/copepods in the mesocosm should be eight times higher during this time period.