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Husbandry procedures can be stressful for captive animals. Knowledge of the physiological effects of these procedures and the reduction of stress during regular maintenance is of pivotal importance to ensure good welfare. Environmental enrichment (EE) can be an asset to animal keepers as it has many benefits on captive animals, including the reduction of stress indicators in many aquatic species. This is particularly relevant for broodstock animals, who may spend years in captivity and who are essential for successful fish farming. We studied whether structural enrichment had a stress-reducing effect on broodstock of gilthead seabream (Sparus aurata) during standard husbandry procedures, monitoring their heart rate with surgically implanted internal bio-loggers (DST milli HRT, Star-Oddi) in 18 fish. These fish were distributed in six tanks, three of which had an EE structure consisting of a 1 m2 floating structure with nine suspended organic cables, while the other three tanks had no enrichment. We added seven more unmarked fish to each tank to simulate broodstock farming conditions (i.e., ten fish per tank). After five days of post-surgical recovery, we tested feeding, netting, and cleaning every day for three consecutive days, and a formaldehyde bath as a prophylactic procedure on the fourth day on the logger-implanted fish and continued to record their recovery for eight more days. Overall, when subjected to stressful husbandry procedures, fish reared under EE show reduced heart rate and amplitude, and faster recovery to baseline levels than non-enriched animals. Our results show that EE can be used to improve the welfare of farmed fish by reducing their stress and should be employed as a good management practice in finfish production, and is especially relevant for high-value fish that spend long periods in captivity, such as spawners.

Environmental enrichment is considered as a recommended tool to guarantee or improve the welfare of captive fish. This study demonstrates for the first time that structural environmental enrichment enhances cognition, exploratory behaviour and brain physiological functions of gilthead seabream (Sparus aurata). Seabream was reared in groups (n = 15) during 60 days under two different treatments: enriched tanks with plant-fibre ropes (EE) or bare/non-enriched tanks (NE). Fish were then exposed to a purpose-built maze for 1 h every second day in four trials. Analysis of video recordings showed that seabream under EE conditions presented higher overall exploratory behaviour, spatial orientation and learning capability compared to seabream from NE conditions. Results from brain monoamines analyses may suggest increased recent dopaminergic activity in telencephalon, known to be involved in learning processes; and increased serotonergic activity in cerebellum, involved in the coordination of balance, movements and orientation. In addition, EE-reared fish showed increased antioxidant activity in whole brain, with no apparent oxidative damage. Structural EE seemed to induce an hormetic response on juvenile seabream, improving their welfare status during captivity. Application of this kind of physical structure might be feasible at fish farms as a passive and non-invasive tool to improve welfare of intensively cultured seabream. [ABSTRACT FROM AUTHOR]

Gilthead sea bream and European sea bass aquaculture is widely established in the Mediterranean and North-eastern Atlantic regions, and rearing is mainly in coastal net-pen facilities. The rapid growth of the fish farming industry increases the potential number of farmed fish in the wild. Escape-related issues are likely to increase unless escape-management policies are included into the aquaculture legislation in the near future. This review summarizes the potential direct interactions among escaped fish and nearby farmed fish stocks, wild conspecifics, and coastal fish populations, since these interactions could compromise sustainability in coastal areas. Socioeconomic implications are also addressed, given that escape events can also lead to economic losses for farmers and may alter local fishery landings. Fish markets and consumers might be also affected. This review compiles the current knowledge on the potential effects of escapees in coastal areas, and contributes to the existing risks analyses regarding sea bream and sea bass escapes. Eventually, the need to design management policies to prevent or minimize escape events and to mitigate further impacts, applicable to Mediterranean countries and of special interest in areas where these species are locally absent, is discussed in the context of sustainable fin-fish aquaculture. [ABSTRACT FROM AUTHOR]

Gilthead sea bream ( Sparus aurata L.) aquaculture has rapidly spread around the Mediterranean Sea. Fish escapes from sea cages are one of the major problems for the industry and also represent a threat to the marine environment. Fishery catches are also influenced by escape events, being mirrored in increased landings of cultured species. However, within the Mediterranean, studies shedding light on the incidence of escaped individuals in fisheries landings are scarce. Firstly, the present study describes a simple scale-examination methodology to distinguish escaped from wild S. aurata landed by coastal fisheries. Secondarily, the incidence of escapees is assessed within landings of the species in the western Mediterranean. The scale readings revealed a monthly incidence of escapees between 11.2 and 20.8%, representing 6.8% of the total income derived from these landings. Moreover, morphological differences between wild fish captured near and far from fish farms point towards escape events as a source of potential genetic admixture between cultured and wild genotypes. Socio-economic and ecological implications of escapees are discussed, and a set of management guidelines proposed, to prevent and/or mitigate the negative influences of escaped fish on the ecosystem and traditional users of the coast such as fisheries. [ABSTRACT FROM AUTHOR]

Trace elements in otoliths of sea bass ( Dicentrarchus labrax L.) and sea bream ( Sparus aurata L.) from fish farms and coastal wild populations in the western Mediterranean Sea were analysed by inductively coupled plasma-mass spectrometry. Results showed that concentrations of Mg, K, and Mn differed significantly between wild and farmed sea bass, while concentrations of Mg, K, Mn, Fe, Zn, Sr, and Ba varied significantly between wild and farmed sea bream. Discriminate analysis and cross-validation classification showed that the trace element profile in otoliths can be used to separate farmed fish from wild stocks with high accuracy on both sea bass (individuals correctly classified: 90.7 %) and sea bream (individuals correctly classified: 96.6 %). Moreover, trace elements in otoliths resulted to be useful to discriminate among wild fish stocks within each species. [ABSTRACT FROM AUTHOR]

The present study compares fin damages in gilthead seabream ( Sparus aurata) and European seabass ( Dicentrarchus labrax) according to their wild, escaped or farmed origins. In addition, the potential applicability of fin condition indices (Fin Erosion Index ' FEI' and Fin Splitting Index ' FSI') as identification tools is discussed. Farmed seabream fins evidenced more erosion and splitting ( FEI ± SD: 2.1 ± 0.3; FSI ± SD: 1.9 ± 0.6) than wild seabream fins ( FEI: 0.8 ± 0.6; FSI: 1.2 ± 0.9), a result of farming conditions in open-sea cages. Escaped seabream fin erosion was between that of farmed and wild seabream ( FEI: 1.6 ± 0.4), which could indicate that fins in farmed fish recover over time from farming abrasions once they are in the wild. However, the fins of escaped seabream seem to be weaker than those of the wild fish, and therefore might be more susceptible to suffer other types of erosion such as splitting or nipping ( FSI: 2.3 ± 0.7). No significant differences were found in seabass FEI according to their origins, although wild seabass presented significantly more split caudal fins ( FSI: 3.3 ± 2.8) than the farmed seabass ( FSI: 1.2 ± 1.1) and escapees ( FSI: 2.5 ± 1.6). Therefore, FEI for seabream could be used as tools not only to distinguish between wild and farmed fish, but also to identify recent escapees, improving further assessments on the contribution of seabream escapees in fishery landings. However, the healing potential of damaged fins must be considered for the proper identification of escapees. Use of fin condition indices from both species could be helpful for aquaculture management, to assess fish welfare in fish farms stocks, and improve the knowledge of handling, stock densities and open-sea cage environment conditions. [ABSTRACT FROM AUTHOR]

Abstract: Escapes of cultured gilthead seabream (Sparus aurata L.) have been recorded throughout the Mediterranean Sea. In the current study we simulated escape incidents of seabream tagged with acoustic transmitters (N =38) or external tags (N =2191). Tagged individuals showed both a high dispersion within the first 5 days after release and a high mortality rate (>60%) where the fish appeared to be predated at the release farm. However, some individuals remained not only at the release farm but also at the nearby farm facilities for long periods, surviving up to 4 weeks with a clear diurnal swimming depth behaviour related to farm activity. Local fisheries contributed largely recapturing tagged individuals that disperse from farm facilities (7.25%), being professional trammel-netters the major contributors (71.5%). Those recaptured individuals were caught on usual fishing grounds and habitats where their wild conspecific live (seagrass, sand or rocky bottoms), feeding on natural preys such as crustaceans and molluscs after one week in the wildness. Therefore, our findings emphasize the negative ecological consequences that escapees might entail to nearby cultured and wild stocks, and the importance of local fisheries to reduce the potential effects of escape incidents on natural stocks. [Copyright &y& Elsevier]

The study of mass and standard length ( LS) relationships showed that farmed individuals had higher values than wild fishes for both gilthead sea bream Sparus aurata and European sea bass Dicentrarchus labrax. Such differences were more pronounced in larger individuals than smaller ones and were more noticeable in S. aurata than in D. labrax. Additionally, differences in external characteristics of scales were detected between origins. A high proportion of farmed S. aurata had a regenerated nucleus (98%) and scale malformations (73%), and there were no annual rings in the farmed D. labrax (100%). Variation in otolith morphology was examined through shape descriptors such as area, perimeter, circularity, roundness, mass, height and length relationship and elliptic Fourier descriptors (EFDs). Important differences were found within geographical origins according to each shape descriptor separately, but no clear patterns distinguished wild and farmed fish. Discriminant analysis with either all shape descriptors together or EFDs was able to classify with high accuracy both S. aurata (89·5-95·7%) and D. labrax (93·2-95·2%) according to their origin. Hence, this study suggests the use of scale characteristics as the easiest and quickest way to distinguish farmed or escaped fishes, and secondly, the usefulness of EFDs or shape descriptors to improve such separation. [ABSTRACT FROM AUTHOR]

Gilthead seabream ( Sparus aurata L.) and European seabass ( Dicentrarchus labrax L.) are important commercial marine fish species both for aquaculture and fisheries in the Mediterranean. It is known that farmed individuals escape from farm facilities, but the extent of escape events is not easy to report and estimate because of the difficulty to distinguish between wild and farmed individuals. In this study, significant differences provided through morphometry evidence that the cranial and body regions of seabream and seabass are different regarding their farm or wild origin at different scales. Morphological variations have been shown to be a valuable tool for describing changes in shape features. Therefore, the biomass contribution of escapees to local habitats could be determined by identifying escaped individuals from fisheries landings as a first step to assess the potential negative effects of fish farm escapees on the environment, and their influence on wild stocks and local fisheries. [ABSTRACT FROM AUTHOR]

Chemical cues from predators induce a range of predator-induced morphological defences (PIMDs) observed across fish taxa. However, the mechanisms, consistency, direction and adaptive value of PIMDs are still poorly studied. Here, we have tested if predatory cues can induce changes in the body shape of the juvenile marine fish Sparus aurata reared under controlled conditions without the presence of predators by exposing individuals to the olfactory stimulus of a fish predator. We tested our hypothesis using a nested replicated before-after-control-impact experiment, including recovery (potential reversibility) after the cessation of the predator stimulus. Differences in the size-independent body shape were explored using landmark-based geometric morphometrics and revealed that, on average, individuals exposed to a predatory cue presented deeper bodies and longer caudal regions, according to our adaptive theoretical predictions. These average plastic responses were reversible after withdrawal of the stimulus and individuals returned to average body shapes. We, therefore, provide evidence supporting innate reversible PIMDs in marine naive fish reared under controlled conditions. The effects at the individual level, including fitness and the associated applied implications, deserve further research.

Considering the overexploitation of fishing on most of the world coasts, the ingestion of fish and shellfish will depend mostly on aquaculture production. Since intensive mariculture usually involves environmental impact, developing sustainable cultures is a priority. In this sense, salt marshes can provide ecosystem services and incorporate both conservation and extensive aquaculture activities. In the present study we compared gilthead seabream Sparus aurata Linnaeus, 1758 cultured in extensive and semi-intensive marsh ponds with wild conspecifics from surrounding coastal areas, using trophic characterization (diet analysis and stable isotopes) and trace metal accumulation. Stomach content analysis revealed different feeding habits among gilthead seabream from different origin. Although wild specimens had the most diverse diet, results of stable isotopes showed that extensive diet had the wider isotopic niche and revealed the highest similarities between wild and extensively cultured gilthead seabream. A similar trace element signature was also measured in wild and extensive culture, whereas the semi-intensive culture showed different concentrations for several elements. Cr, Fe and Mn showed the highest concentrations in semi-intensive cultured fish, while As and Zn showed the lowest values in this group. In any case, average values measured in both extensive and semi-intensive culture were, in general terms, below the hazardous limits provided by the standards recommended for trace metals by national and international regulations. Therefore, marsh ponds provide a suitable environment where the cultured fish, especially extensive, should be promoted. • Sparus aurata cultured in marsh ponds are compared with wild populations. • Integrative approach based on diet, stable isotopes and trace metals was used. • High similarities were obtained between wild and extensively cultured gilthead seabream. • Extensive farming in marsh ponds should be enhanced. [ABSTRACT FROM AUTHOR]