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Introduction: The availability of high-quality gilthead seabream (Sparus aurata) larvae in larviculture represents a major bottleneck to the aquaculture. This challenge can be compounded by losses resulting from the emergence of a clinical disorder's symptomatology. In this study, the observed syndrome included a rotated positioning of the larval sagittal plane and in most cases leading eventually to death. Methods: Herein, we examined using amplicon sequencing of the 16S rDNA the bacterial communities associated with S. aurata larvae at different conditions (including both fish with no evidence of the syndrome and fish with syndrome) during the early developmental stages along with the contribution of rearing water, organic matter and provided feed in the microbiota during an experiment of 18 days. Results: Over the development of larvae, differences were observed in the bacterial composition between healthy and symptomatic larvae as well as between components of the system. A remarkable presence of members of the Psychrobacter genus was observed in symptomatic larvaewith a significant increase at 18dph. The healthy larvae harbor different bacterial profile with a dominance of Vibrio and Bacillus genera during 3-8dph, various members of Alphaproteobacteria during 11-14dph and Marinifilum at 18dph. The rearing water showed a different bacterial profile compared to the other components, with a slight effect of healthy larvae at 3-8dph. The bacteriome of feeds provided during the rearing of larvae was found to be diverse. Chlorella was mainly dominated by members of Firmicutes, while Rotifer and Artemia were mainly dominated bymembers of Proteobacteria including different species of Psychrobacter. At 18dph, Artemia feed seems to affect the symptomatic larvae bacteriome, where it enhanced the presence of Psychrobacter spp. Discussion: Interestingly, the comparative network analysis at 18dph indicated that the bacterial associations in symptomatic larvae were primarily driven by members of the Psychrobacter genus. While various phyla contributed to bacterial associations in healthy larvae with different frequencies including mainly members of Proteobacteria, Bacteroidota and Firmicutes phyla. Finally, the Gammaproteobacteria/Alphaproteobacteria ratio was found to be related to the health condition of larvae. This study provides valuable informationwhich can be used as indicators for monitoring the health status of S. aurata larvae. [ABSTRACT FROM AUTHOR]

Introduction: The availability of high-quality gilthead seabream (Sparus aurata) larvae in larviculture represents a major bottleneck to the aquaculture. This challenge can be compounded by losses resulting from the emergence of a clinical disorder's symptomatology. In this study, the observed syndrome included a rotated positioning of the larval sagittal plane and in most cases leading eventually to death. Methods: Herein, we examined using amplicon sequencing of the 16S rDNA the bacterial communities associated with S. aurata larvae at different conditions (including both fish with no evidence of the syndrome and fish with syndrome) during the early developmental stages along with the contribution of rearing water, organic matter and provided feed in the microbiota during an experiment of 18 days. Results: Over the development of larvae, differences were observed in the bacterial composition between healthy and symptomatic larvae as well as between components of the system. A remarkable presence of members of the Psychrobacter genus was observed in symptomatic larvaewith a significant increase at 18dph. The healthy larvae harbor different bacterial profile with a dominance of Vibrio and Bacillus genera during 3-8dph, various members of Alphaproteobacteria during 11-14dph and Marinifilum at 18dph. The rearing water showed a different bacterial profile compared to the other components, with a slight effect of healthy larvae at 3-8dph. The bacteriome of feeds provided during the rearing of larvae was found to be diverse. Chlorella was mainly dominated by members of Firmicutes, while Rotifer and Artemia were mainly dominated bymembers of Proteobacteria including different species of Psychrobacter. At 18dph, Artemia feed seems to affect the symptomatic larvae bacteriome, where it enhanced the presence of Psychrobacter spp. Discussion: Interestingly, the comparative network analysis at 18dph indicated that the bacterial associations in symptomatic larvae were primarily driven by members of the Psychrobacter genus. While various phyla contributed to bacterial associations in healthy larvae with different frequencies including mainly members of Proteobacteria, Bacteroidota and Firmicutes phyla. Finally, the Gammaproteobacteria/Alphaproteobacteria ratio was found to be related to the health condition of larvae. This study provides valuable informationwhich can be used as indicators for monitoring the health status of S. aurata larvae. [ABSTRACT FROM AUTHOR]

Reliable stock identification constitutes an integral component of effective fishery management. Current methods for the identification of putative stock units comprise the analysis of both phenotypic and genetic variability. The present study examined the spatial variation in otolith morphology (shape and asymmetry) and genetic composition of 395 wild-caught Gilthead seabream (Sparus aurata) specimens, collected from the Aegean and Ionian Seas (eastern Mediterranean) between 2014–2018. The degree of scale regeneration (SRD, % of regenerated scales) was used as an indicator to assess the potential presence of aquaculture escapees in the wild-caught samples. Otolith shape and asymmetry analyses showed a phenotypic discrimination between northwestern Aegean and Ionian Gilthead seabream populations. Genetic analyses of nine microsatellite markers revealed higher levels of genetic variation in the wild compared with samples obtained from aquaculture farms. Despite the absence of genetic structure among the wild-caught seabream populations, a low but statistically significant genetic differentiation was found between reared fish and fish collected in the field. The SRD was considered effective in detecting the presence of aquaculture escapees that may have escaped in either early or late rearing phases. [ABSTRACT FROM AUTHOR]

The anabolic effect of exercise on muscles and bones is well documented. In teleost fish, exercise has been shown to accelerate skeletogenesis, to increase bone volume, and to change the shape of vertebral bodies. Still, increased swimming has also been reported to induce malformations of the teleost vertebral column, particularly lordosis. This study examines whether zebrafish (Danio rerio) develops lordosis as a result of continuous physical exercise. Zebrafish were subjected, for 1 week, to an increased swimming exercise of 5.0, 6.5 or 8.0 total body lengths (TL) per second. Control and exercise group zebrafish were examined for the presence of vertebral abnormalities, by in vivo examination, whole mount staining for bone and cartilage and histology and micro‐computed tomography (CT) scanning. Exercise zebrafish developed a significantly higher rate of lordosis in the haemal part of the vertebral column. At the end of the experiment, the frequency of lordosis in the control groups was 0.5 ± 1.3% and that in the exercise groups was 7.5 ± 10.6%, 47.5 ± 10.6% and 92.5 ± 6.0% of 5.0, 6.5 and 8.0 TL∙s−1, respectively. Histological analysis and CT scanning revealed abnormal vertebrae with dorsal folding of the vertebral body end plates. Possible mechanisms that trigger lordotic spine malformations are discussed. This is the first study to report a quick, reliable and welfare‐compatible method of inducing skeletal abnormalities in a vertebrate model during the post‐embryonic period. [ABSTRACT FROM AUTHOR]

Otolith structure is a useful tool in discrimination among fish populations as it is a permanent record of the influence of endogenous and exogenous factors. In the present study we examined otolith morphology and fluctuating asymmetry (FA) for differences between wild‐caught (by bottom trawl) and reared specimens of Gilthead seabream (Sparus aurata). Based on the frequency of regenerated scales (degree of scale regeneration, SRD) on each specimen, a threshold of 30% SRD was used to assign wild‐caught fish individuals as wild (≤30% SRD, LR group) or as possible aquaculture escapees (>30% SRD, HR group). Based on the analysis of elliptic Fourier descriptors, significant differences were found in otolith shape between reared (Rr) and the wild‐caught groups (LR, HR). Reared fish had otoliths with significantly larger perimeter (OP) than wild‐caught fish. Furthermore, FA was significantly higher in the Rr than the LR group for OP and all except one shape descriptors (harmonics 2–7). The HR group exhibited intermediate levels of FA between the low and high FA levels observed in the LR and Rr groups. Results are discussed in terms of the value of combining otolith and scale morphology for the identification of escapees in wild Gilthead seabream stocks. [ABSTRACT FROM AUTHOR]

Keywords: aquaculture; finfish; heritability; skeletal abnormalities EN aquaculture finfish heritability skeletal abnormalities 825 828 4 06/15/20 20200701 NES 200701 In the last years, there is an increasing evidence for a significant genetic component of variation in the development of certain types of skeletal deformities, in species like I Salmo salar i (vertebral deformities, Gjerde, Pante, & Baeverfjord, [9]), I Dicentrarchus labrax i (vertebral deformities, Bardon et al., [1]), I Sparus aurata i (cranial and vertebral deformities, Fragkoulis, Batargias, Kolios, & Koumoundouros, [7]; Negrín-Báez et al., [16]) and I Seriola lalandi i (cranial deformities, Nguyen, Whatmore, Miller, & Knibb, [17]). Results show a remarkable variation in terms of heritability estimates, which among other reasons is attributed to the lack of precision of abnormality scoring and to the difficulty of appropriately and biologically defining the traits in the study. In this study, we estimated the genetic parameters of caudal fin abnormalities in Gilthead seabream ( I S. aurata i Linnaeus, 1758) at the early metamorphosis period, where the development of caudal fin abnormalities has been completed (Koumoundouros, [11]). [Extracted from the article]

The goal of the present study was to develop a simple morphometric index that could link lordosis severity at the juvenile stage with fish body shape at harvesting, without requiring to kill the fish. Skeletal abnormalities develop frequently in reared fish, with a great variability in terms of the affected anatomical area and their effects on fish external morphology. Simple morphometrics for predicting lordosis-induced deviations of body shape in reared Gilthead seabream (Sparusaurata L.). [Extracted from the article]

Morphometric characters have traditionally been used to describe the population structure of fishes. Body shape variation, which is often environmentally induced, may provide a good record of short-term population structuring. However, factors unrelated to environmental or genetic influences on body morphology may complicate sampling and the use of morphometric features for stock discrimination. In the present study, we used geometric morphometric variables to compare the European sardine Sardina pilchardus putative stocks of the Aegean and Ionian Seas (eastern Mediterranean). Landmark data of fish collected at seven different sites were subjected to canonical analysis of principal coordinates (CAP). The average body condition of sardines from these sites was strongly and linearly related to corresponding scores along CAP1, the axis exhibiting the highest correlation with the morphometric data cloud. The average scores along CAP2 and CAP3 appeared to be linked to morphological differentiation related to temperature effects and prey availability (mesozooplankton biomass). Despite the primary and confounding effect of body condition, discrimination of different morphotypes corresponding to the Aegean and the Ionian Sea stocks was highly significant with 81% correct reallocations for the respective CAP model. [ABSTRACT FROM AUTHOR]

In this study, a scale of quality for the body shape of Gilthead seabream was developed. For this purpose, a questionnaire survey was carried out to study the preferences of consumers for the body shape of seabream. Furthermore, the variation in body shape in reared seabream was studied under two rearing environments (sea cages vs. tanks) and in comparison with wild-caught individuals. Following the test-retest analysis of reliability, the 22 of 65 participants in the survey presented a significant correlation between repeated evaluations of the same subjects and were classified as responders of high discrimination efficiency or/and reliability ( HDR). Geometric morphometric analysis on the evaluation of HDR responders revealed that compared with the fish of fair body shape, fish with preferred body shape were characterized mainly by a more proximal position of the base of the pelvic fins, the anterior base of the anal fin and the anterior dorsal fin. Of the 45 wild-caught specimens examined, 26 presented a normal lateral line and no obvious skeletal deformities. The body shape of the normal wild-caught fish was compared with the shape of reared seabream. Results showed that both the origin of fish (wild vs. reared) and the rearing methodology during the on-growing phase significantly affected the body shape of seabream ( P < 0.001). Compared with the reared fish, the wild-caught fish were characterized mainly by a less prominent belly, slender trunk, smaller head, shorter caudal peduncle and a more posterior-ventral position of the upper jaw. [ABSTRACT FROM AUTHOR]