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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.
- Response of gilthead seabream (Sparus aurata L., 1758) larvae to nursery odor cues as described by a new set of behavioral indexesPublication . Morais, Pedro; Parra, María P.; Baptista, Vânia; Ribeiro, Laura; Pousão-Ferreira, Pedro; Teodosio, MariaTemperate marine fish larvae use a series of environmental cues (e.g., olfactory, hearing, visual) to mediate the selection of nursery habitats. However, habitat selection may vary according to individuals' physiological condition. Therefore, this study aimed to determine the ability of gilthead seabream (Sparus aurata L., 1758) larvae to utilize natural odor cues to locate nursery habitats along ontogeny and to examine how it varies with individual's physiological condition. The hypothesis being tested is that S. aurata larvae prefer coastal rocky reefs as nursery areas, but they might use coastal lagoons as nursery grounds—ecosystems known for their productivity—if under starvation conditions, as a compensatory mechanism to avoid slow growth or even death. A choice-chamber experiment was used to investigate the behavioral responses of satiated and starved laboratory-reared S. aurata larvae, along ontogeny (pre-flexion, flexion, post-flexion), to water collected in a coastal artificial rocky reef and a coastal lagoon. The physiological condition of S. aurata larvae was determined by analyzing several biochemical condition indices. Complementarily, a new set of four preference indexes were developed—Choice-Chamber Preference Indexes—and discussed to provide a clear measure of the behavioral changes of a species along ontogeny by balancing all the behavioral choices made during the experimental trials, including the unresponsive behavior. A developmental threshold was identified at 24 days post-hatching, before which insufficient swimming capability disabled responsive behavior. Beyond this threshold, post-flexion larvae preferred rocky coastal water over lagoon water, even if under starvation conditions or poor physiological condition, despite the fact that the unresponsive behavior was largely predominant. S. aurata larvae displayed a cautionary behavioral strategy, so the compensatory mechanisms to ensure metapopulation stability and resilience have to rely on their feeding plasticity and on being a batch-spawning species (i.e., diversified bet-hedging strategy) to compensate the lack of apparent behavioral plasticity.