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The recent fast development of the microalgae-related biotechnologies has enabled the availability of sustainable and nutrients-rich raw materials to be used as substitution of conventional sources in aquafeed formulation. However the cost of energy of the photobioreactors used to produce these microorganisms still constrained their wider inclusion into aquafeed compounds. By exploiting industrial waste outputs, Nannochloropsis sp. and Spirulina sp. were produced and utilised to formulate two experimental enrichments (LM1 and LM2). During a 60 days trial, their efficacy have been tested as Artemia metanauplii enrichments in the diet of European seabass (Dicentrarchus labrax) larvae, in comparison to a commercial control. Larvae were fed with isonitrogenous and isolipidic dietary treatments. Each dietary treatment presented a specific profile for the long chain polyunsaturated fatty acids ARA, DHA and EPA. Ratio of DHA/EPA in enriched Artemia of 4:1 as in the case of LM1 and LM2 in the presence of 1.4% of ARA (as a % on total fatty acid) guaranteed equal results to the control which displayed a ratio of DHA/EPA of 2:1 with 2.2% of ARA. No significant effects of the dietary treatments were detected in final survival, growth performance and incidence of skeletal anomalies. Regarding oxidative status, larvae fed with LM2 enrichment presented lower catalase activity than control larvae with no signs of oxidative damage, suggesting a potential antioxidant effect of LM2. The present study contributes to expanding the existing literature on successful utilisation of microalgae and cyanobacteria, used to produce valuable nutrients, in a perspective of circular nutrients economy

[EN] Different strategies have been followed to improve the aquaculture of main European farmed fish, such as genetic selection, refinements in culture conditions or enhanced feed formulation and management. However, more knowledge is required to exploit fish phenotypic plasticity to obtain those that better match aquaculture or market conditions. The overall objective of this mini-review is to identify the latest productive traits recently performed, mainly in commercial carnivorous species, and underlying biological processes that would be susceptible to improve the competitivity of aquaculture sector through nutritional issues. Thus, this work is framed within the concepts of Circular Economy and Blue Growth, where it is intended to point out the use of natural compounds extracted from seaweeds, microalgae and by-products of the industry for their inclusion in aquafeeds, allowing a more efficient use of more sustainable vegetable protein sources, and also to evaluate if these nutraceutical compounds counteract detrimental effects observed by nutritional interventions or environmentally challenged., [ES] La producción acuícola ha seguido diferentes estrategias para su optimización a lo largo de las últimas décadas, como el desarrollo de la selección genética, la mejora de las condiciones de cultivo, o el avance en la formulación y gestión de los piensos. Sin embargo, se requiere más conocimiento para explotar la plasticidad fenotípica de los peces para obtener aquellos que se ajusten mejor a las condiciones de la acuicultura o del mercado. El objetivo general de esta mini-revisión es identificar los últimos avances realizados recientemente, principalmente en especies carnívoras comerciales, y los procesos biológicos subyacentes que serían susceptibles de mejorar la competitividad del sector acuícola a través de intervenciones nutricionales. Así, este trabajo se enmarca dentro de los conceptos de Economía Circular y Crecimiento Azul, donde se pretende señalar el uso de compuestos naturales extraídos de algas, microalgas y subproductos de la industria para su inclusión en alimentos acuícolas, permitiendo un uso más eficiente de fuentes de proteínas vegetales más sostenibles, y también evaluar si estos compuestos nutracéuticos son capaces de contrarrestar los efectos perjudiciales observados por las formulaciones inadecuadas o desafiados por factores ambientales estresantes.

Growth rate in farmed fish is the phenotypic trait of major relevance for the aquaculture industry. Several strategies have been followed to increase growth rate in fish such as genetic selection and improvements in diet formulation. Somatic growth in fish, as in other vertebrates, is mainly controlled by the growth hormone (GH) / insulin-like growth factor I (IGF-I) axis. The molecular and physiological features of this axis have been thoroughly studied in several vertebrates. In fish, GH/IGF-I axis functionality in fish depends on endogenous and environmental factors such as genetic polymorphisms and nutritional status. There are now several evidences that fish GH-IGF-I axis can be modulated also by epigenetic mechanisms such as DNA methylation. However, the role of epigenetics in regulating this axis in fish is far from being understood as results, in addition to sparse, are poorly consistent among species regarding genes affected. The present study aimed to evaluate ex-vivo models for epigenetic studies in Sparus aurata and to provide the first assessment in this species of the putative role of DNA methylation on the modulation of GH/IGF-I axis.

The digestive tract houses a complex and metabolically active consortium of microorganisms that plays critical roles in the nutrition and health of the host. In the last years, many studies have focused on bacterial community composition in different animal species and how it responds to different variables. However, there is limited information about how these responses can generate community dynamics at different time scales, such as circadian rhythms. The aim of the present study was to characterize variations along a daily cycle in the gut microbiota of fish on different feeding regimes. The greater amberjack (Seriola dumerili) was used as experimental species, a promising species for Mediterranean aquaculture. Fish were randomly distributed in two different feeding regimes, in triplicate rearing tanks. Feeding regimes were continuous feeding and intermittent feeding (three meals per day), both under continuous illumination. Water temperature was 22 ºC. Fish feces for microbiota analysis were sampled along a 24h cycle. qPCR results revealed a synchronization between the bacterial cellular cycle and feeding. In continuously-fed fish bacterial density and activity were kept at constant levels along the day cycle. By contrast, in intermittent fed fish there was an increase in specific bacterial activity (16S rRNA:16S rDNA ratio) 2 hours after the first meal of the day, while the highest levels of protein synthesis (16S rRNA) and bacterial abundance (16S rDNA) were registered at 12 and 16 h after first-feeding, respectively. Intermittent-fed fish exhibited changes in the composition of the active bacterial community promoted by feeding, thus revealing two types of bacterial community profiles: “pre-feeding” and “active-feeder” profiles. Continuous-fed fish maintained an “activefeeder” community profile throughout the whole day. Bray-Curtis and Sørensen similarity indicated that differences in the composition between the two community profiles were mainly driven by t

The increasing incorporation of plant-based products in fish feed warrants consideration of potential unintended factors, including the presence of new plant toxins. To enhance risk assessments in animal studies, the utilization of early response biomarkers has been proposed. This study aims to explore the interaction between an experimental diet and the gut integrity in juveniles of greater amberjack (Seriola dumerili), focusing on the effects of corn gluten feed as a plant-based ingredient obtained as by-product from the cereal industrial processing. Various biomarkers of exposure and effects were evaluated, including histochemical properties of goblet cells, morphological changes in the posterior intestine (villus length, variations in size and number of goblet cells), and alterations in cell proliferation using the proliferating cell nuclear antigen (PCNA) approach.

Temperature is a key factor for achieving optimum fish growth and keep the welfare of the culture. Indeed, an incorrect temperature can affect ingestion, transit, digestion, assimilation and metabolism. Furthermore, this is magnified in a fastgrowing fish such as the greater amberjack (Seriola dumerili). The culture of this species is becoming more and more important in the Mediterranean coasts mainly because of its fast development, its meat quality and its good acceptance in the market. For all these reasons, it is of utmost importance to establish a proper temperature, especially in RAS systems where this parameter can be modified quite easily, although its monitoring is especially important to avoid secondary artifacts that could compromise the metabolic and intestinal well-being of cultured fish. Taking all this into account, the aim of this study was to establish the consequences of water temperature on welfare, metabolic orchestration and intestinal integrity of greater amberjack juveniles accompanying the observed differences in growth performance (Yúfera et al., this conference).

[EN] One main challenge of aquaculture sector is the need for sustainable fish feeds. Fishmeal content in aquafeeds has progressively declined for the major farmed marine species produced in Europe, being mainly replaced by plant ingredients. However, some plant ingredients may pose contrasts in sustainability and resource efficiency, as these resources are preferentially used for human consumption. The abundant amounts of agricultural byproducts might represent sustainable and low-cost feedstocks for fish feeding, with limited competition with human food consumption and independence on seasonal quality fluctuations. The present work presents a case study testing and validating less/zero competing feeds for on-growing greater amberjack (Seriola dumerili) by using a balanced mixture of vegetable by-products to reduce ingredients that could be eaten directly by humans. Overall quality assessment of fish fed the new aquafeeds was determined to identify possible implications of the new ingredients on fish products., [ES] Uno de los principales desafíos del sector acuícola es la necesidad de nuevos ingredientes sostenibles para la formulación de piensos. El contenido de harina de pescado en los piensos ha disminuido progresivamente para las principales especies marinas producidas en Europa, siendo reemplazada principalmente por ingredientes vegetales. Sin embargo, algunos ingredientes vegetales pueden generar controversias en la sostenibilidad y la eficiencia de los recursos, ya que son alimentos preferentemente destinados para el consumo humano. Las altas cantidades de subproductos agrícolas podrían representar materias primas sostenibles y de bajo costo para la alimentación de los peces, con competencia limitada con el consumo humano e independencia de las fluctuaciones estacionales de calidad. El presente trabajo presenta un caso práctico que testa y valida nuevos piensos para el pez limón (Seriola dumerili) en fase de engorde que incluyen una mezcla equilibrada de subproductos vegetales con el objetivo de reducir los ingredientes que son competidores directos con la alimentación humana. Para ello se analizó la calidad general de los individuos alimentados con los nuevos ingredientes para identificar sus posibles implicaciones en el producto final.

[EN] Aquaculture is the best bet for the future to face the great challenge of providing food to a population that will reach 9 billion people in 2050. However, to increase the production performance of aquaculture in a sustainable way, it is necessary to develop strategies, such as species diversification or the use of more sustainable diets. In this respect, the greater amberjack (Seriola dumerili) is a good candidate both for its high biological and economic potential. However, as a carnivorous species, it has high protein requirements, most of which from fish meal. Therefore, it is essential to replace ingredients of animal origin with more sustainable ones such as plant raw materials. However, diets with a high content of vegetable ingredients can affect the bioavailability and digestibility of nutrients causing negative effects on fish growth and health. Nevertheless, the use of biotechnological pretreatments of plant ingredients and the inclusion of nutraceutical compounds have allowed to improve the use of these nutrients, providing good growth and health status of a highly carnivorous species such as greater amberjack., [ES] La acuicultura es la mejor apuesta de futuro para hacer frente al gran desafío de proporcionar alimentos a una población que superará los 9 billones de personas en 2050. Sin embargo, para incrementar el rendimiento de la producción acuícola de manera sostenible es necesario desarrollar estrategias como la diversificación de especies o el uso de dietas más sostenibles. En este sentido, la seriola o pez limón (Seriola dumerili), es un buen candidato tanto por su gran potencial biológico como económico. Sin embargo, como especie carnívora, presenta unos altos requerimientos de proteínas, procedentes la mayor parte de las harinas de pescado. Por tanto, es imprescindible la sustitución de ingredientes de origen animal por otros más sostenibles como las materias primas vegetales. Aun así, dietas con un alto contenido de ingredientes vegetales pueden afectar a la biodisponibilidad y digestibilidad de los nutrientes causando efectos negativos sobre el crecimiento y la salud de los peces. Sin embargo, el uso de pretratamientos biotecnológicos de los ingredientes vegetales y la inclusión de compuestos nutraceúticos han permitido un buen uso de los nutrientes presentes en estas dietas, proporcionando un buen crecimiento y estado de salud en una especie altamente carnívora como la seriola.

Gut microbial communities are highly dynamic and respond to factors such as diet and host metabolism. However, there is limited knowledge on gut microbiota changes during the daily cycle. In aquaculture, the characterization of gut microbiome dynamics is necessary to identify and understand the relationship it have on host physiology and fitness. To investigate how interactions between feeding and water temperature affected the diel dynamics and activity of the microbiota, we performed two experiments with water temperature and feeding regime as experimental variables, respectively. The qualitative and quantitative composition of the active bacterial community in feces was analyzed along a day cycle in greater amberjack (Seriola dumerili) juveniles.

The cereal industry generates large amounts of residual by-products with high potential as feed ingredient for aquafeeds. Such raw materials could help to substitute protein and lipids from less sustainable sources such as soy concentrate, wheat flour or oils and reduce the competitiveness between the production of aquafeeds and the use of food for human consumption. In this study, one of these by-products, corn gluten feed, has been tested in dose-response experiments as ingredients in on-growing feeds for two European species (greater amberjack, Seriola dumerili; gilthead seabream, Sparus aurata). The final aim was to examine to what extent this more-sustainable and low-cost product can be used as alternate ingredient for fish feeds.

A good knowledge of the potential effects of water temperature on feeding and on-growing process is of primary importance to optimize the fish production. Temperature modulates ingestion, transit, digestion, assimilation, metabolism and ultimately feed utilization and growth rate. These two last parameters, together with the cost of feeds and energy, are necessary data for producers to make decisions. The production in indoor facilities with temperature control is depending on energy cost while in outdoor facilities (ponds and cages) it depends on environmental temperature. The effect of temperature is more noticeable in fast growing fish, as the greater amberjack (Seriola dumerili), a species of great interest for the aquaculture industry worldwide. Currently, its cultivation is expanding in the Mediterranean countries. Therefore, it constitutes a good model to study the consequences of an increased temperature. In this study, we examined the ingestion, digestive enzyme activities, metabolites in plasma and liver, antioxidant response in the liver and the integrity and electrogenic amino acid transport in the intestine, in greater amberjack juveniles growing at three different temperatures. The final aim was to elucidate the mechanisms behind feed utilization that justify the growth differences and to provide a useful informative basis to the productive sector.

Aquaculture is probably the fastest-growing food-producing sector, accounting for nearly 50 percent of the world’s food fish [...]

Feed passage time throughout the digestive tract of three daily consecutive meals containing three different inert markers respectively and the gut luminal ionic conditions generated during a daily cycle have been examined in juveniles of greater amberjack (Seriola dumerili) growing at 18, 22 and 26 °C of water temperature. As expected, transit time tended to decrease with increasing temperature in the tested range. However, each meal progressed in a different manner affecting the ionic daily pattern within the tract lumen and the residence time within the different gut segments, two parameters of primary importance for the digestion efficiency. At 22 and 26 °C the gastric acidification effort was focused on the first meal whilst at 18 °C it was on the second and third meal. Intestinal alkalinisation was maintained during more hours at 22 °C than at 18 °C and 26 °C coinciding with the moments of highest chyme content in the intestine. At 26 °C, the three meals transited fast enough to progress clearly as separate batches. On the contrary, at 18 and 22 °C the consecutive meals became mixed in the stomach and intestine. Transit time was progressively shorter from the first to third meals at 18 and 22 °C, while at 26 °C it was shorter for the second meal and similar for the first and third meals when 95% total gut evacuation was considered. Total transit time ranged from 12 to 24 h approximately and the posterior intestine was completely emptied before the first morning meal in all cases. Interestingly, the residence time of ingested food in the middle intestine was longer at 22 °C than at the other two temperatures.

Gut microbial communities are highly dynamic and respond to factors such as diet and host metabolism. However, there is limited knowledge on changes in gut microbiota during the daily cycle. To investigate how interactions between feeding and water temperature affected the diurnal dynamics and activity of the microbiota, we analyzed the qualitative and quantitative composition in feces of the potentially active bacterial community along a day cycle in greater amberjack juveniles (Seriola dumerili). Bacterial density (based on qPCR of 16S rDNA) in feces was relatively stable along the day. In contrast bacterial activity (based on qPCR of 16S rRNA) increased during the period of active feeding, and was reduced to pre-feeding levels four hours after the last meal. The relative potential activity of the bacterial community in fish feces varied with postprandial time. At the phylum level there was a shift from a Spirochaetes-dominated community in the morning to increased potential activity of Proteobacteria after feeding. At lower taxonomic level, i.e. order, the bacterial community was dominated by Mycoplasmoidales, which relative potential activity was maintained throughout the day in all treatments. By contrast, for absolute potential bacterial activity at the order level there was a peak in potential activity of several bacterial orders at 6h after first feeding, with the most noticeable increase observed for Mycoplasmoidales. Results from the present work also indicated a close relation between the effect of water temperature and microbial dynamics. This is the first study assessing the quantitative and qualitative effects of water temperature and daily feeding rhythm on the gut microbiota dynamics in fish. Feeding was the main driver modulating bacterial activity, promoting a peak in bacterial activity 6h after first feeding. However, water temperature also modulated gut microbiota dynamics, with a marked effect on the time scale. In addition, results indicate tha

Food and feed shortage are serious problems challenging the sustainable development of human society. Besides, food-related health is becoming an emerging topic attracting researchers' attentions...

The study of fish digestive biochemistry is essential to understand factors that affect the net efficiency of food transformation and growth, and therefore aquaculture profitability. The aim of the present study was to assess the activity and functional characteristics of key digestive enzymes in juveniles of greater amberjack (Seriola dumerili), as well as the possible modulation of their relative importance by water temperature. For that, a combination of biochemical assays and substrate-SDS-PAGE were used. Under physiological conditions pepsin activity was negligible. Chymotrypsin was the most active enzyme in the digestive tract of the greater amberjack, while lipase was the enzyme with lower activity, though both enzymes in addition to trypsin were responsive to water temperature as revealed by discriminant analysis. Seriola dumerili showed to have pH-sensitive and, except for chymotrypsin, thermally robust proteases. Inhibition assays showed the major importance of serine proteases and revealed inverse trypsin and chymotrypsin responses to environmental temperature, with higher trypsin contribution in 26°C-fish while higher chymotrypsin contribution in 18°C-fish. Zymograms revealed three isotrypsin and three isochymotrypsin enzymes, with no variation in the presence of particular isoforms among rearing temperatures. However, they confirmed the role of chymotrypsin activity in providing digestive plasticity, with one of the isoforms being more active at lower temperatures. Thus, results indicate that variation in the relative contribution of chymotrypsin isoenzymes to a particular environmental temperature occurs due to different physic-chemical features of isoforms as a source of functional flexibility. This study assessed for the first time the effects of rearing temperature on greater amberjack digestive enzymes, increasing the knowledge on its digestive biochemistry, and aiding in the improvement of management practices for this species industrialization.

The study of fish digestive biochemistry is essential to understand factors that affect the net efficiency of food transformation and growth, and therefore aquaculture profitability. The aim of the present study was to assess the activity and functional characteristics of key digestive enzymes in juveniles of greater amberjack (Seriola dumerili), as well as the possible modulation of their relative importance by water temperature. For that, a combination of biochemical assays and substrate-SDS-PAGE were used. Under physiological conditions pepsin activity was negligible. Chymotrypsin was the most active enzyme in the digestive tract of the greater amberjack, while lipase was the enzyme with lower activity, though both enzymes in addition to trypsin were responsive to water temperature as revealed by discriminant analysis. Seriola dumerili showed to have pH-sensitive and, except for chymotrypsin, thermally robust proteases. Inhibition assays showed the major importance of serine proteases and revealed inverse trypsin and chymotrypsin responses to environmental temperature, with higher trypsin contribution in 26°C-fish while higher chymotrypsin contribution in 18°C-fish. Zymograms revealed three isotrypsin and three isochymotrypsin enzymes, with no variation in the presence of particular isoforms among rearing temperatures. However, they confirmed the role of chymotrypsin activity in providing digestive plasticity, with one of the isoforms being more active at lower temperatures. Thus, results indicate that variation in the relative contribution of chymotrypsin isoenzymes to a particular environmental temperature occurs due to different physic-chemical features of isoforms as a source of functional flexibility. This study assessed for the first time the effects of rearing temperature on greater amberjack digestive enzymes, increasing the knowledge on its digestive biochemistry, and aiding in the improvement of management practices for this species industrialization.

An imbalance in the production and detoxification of reactive oxygen species and other oxidants can disrupt all types of cellular compounds, and lead to a state of oxidative stress. Preventing this state is essential to improve growth and health in animal production. Therefore, the aim of this work was to assess if the dietary supplementation of curcumin could improve the antioxidant status and intestine structure and functionality of gilthead seabream postlarvae, with the global objective of improving fish growth performance and robustness. Two experimental diets supplemented with different doses of curcumin (LOW and HIGH diets), and a commercial diet were fed to quadruplicate groups of postlarvae, for 20 days. At the end of the feeding trial fish fed the supplemented diets significantly improved their antioxidant status compared to CTRL fed fish. LOW and HIGH fed fish presented lower protein oxidative damage (P < 0.05) and higher total antioxidant capacity (P < 0.05). Moreover, postlarvae fed curcumin supplemented diets also presented an upregulation of nuclear factor erythroid 2 – related factor 2 (nrf2) and glutathione-disulfide reductase (gr) in HIGH (P < 0.05) and heat shock protein 70 (hsp70) in LOW treatments (P < 0.05). No differences were observed in growth performance, intestine morphometry, and digestive enzymes activities among treatments (P > 0.05). In conclusion, dietary curcumin supplementation was able to enhance gilthead seabream postlarvae robustness through a modulation of the oxidative status, increasing total antioxidant capacity and decreasing protein oxidative damage. This data provide evidence that curcumin can be a suitable feed additive to promote heath status and robustness of fish at early stages of development, therefore contributing for the development and sustainability of marine fish hatchery production.

The digestive tract houses a consortium of microorganisms that plays critical roles in the nutrition and health of the host. Gut microbiota changes during the daily cycle, however, there is limited knowledge on absolute (vs. relative) temporal microbiota abundance variation (Vandeputte et al., 2021). Water temperature is a crucial factor in fish production, influencing among others feed intake and transit time. The aim of the present study was to assess the effect of rearing temperature and daily feeding rhythms on the fish gut microbiota. The greater amberjack (Seriola dumerili) was used as experimental species, a promising species for the diversification of Mediterranean aquaculture. Fish were randomly distributed in three independent RAS systems set to 18, 22 and 26°C. Juveniles were reared for 12 days and fed ad libitum three times daily with a commercial diet. Then, nine fish per temperature were sampled every 6 h for 24 h for fecal microbiota analysis. Results from 16S rDNA qPCR revealed no effect of temperature and sampling time on bacterial abundance per mg of gut content. By contrast, when focusing on the quantity of active cells (qPCR of 16S rRNA), differences with respect to sampling time but not temperature, were observed. The bacterial activity increased a factor 30 due to feeding but was reduced to prefeeding levels four hours after the last meal. This pattern was also observed in the specific bacterial activity (RNA:DNA ratio), with almost 2 orders of magnitude increase during the period of active feeding. At 18°C a higher dispersion in the results was observed, probably because of the slower gut transit time. Regarding community composition, feeding promoted an increase in the relative and absolute abundance of the order Vibrionales. In conclusion, this is the first study assessing the quantitative and qualitative effects of water temperature and daily feeding rhythm on the gut microbiota in fish. Feeding was the main driver modulating bacterial acti

[ES] En los últimos años la investigación en acuicultura se ha enfocado en la diversificación de especies, así como en la búsqueda de ingredientes alternativos para abaratar los piensos y hacerlos más sostenibles. El presente estudio tiene como objetivo la evaluación de subproductos de cereales como fuentes alternativas y más sostenibles a los ingredientes convencionales de origen marino. Para ello juveniles de seriola (Seriola dumerili) fueron alimentados con diferentes dietas formuladas con subproductos del trigo y el maíz. Se analizaron los metabolitos en plasma y biomarcadores del estrés oxidativo en hígado. No se obtuvieron diferencias significativas en las variables analizadas, por lo que los resultados sugieren que los ingredientes alternativos testados son buenos sustitutos en la formulación de piensos en acuicultura., [EN] In the last years, aquaculture’s research is focused on species diversification and the search for alternative ingredients to make feed more sustainable and cheaper. The aim of this study was the evaluation of cereal by-products as a more sustainable alternative to conventional marine ingredients. For that, greater amberjack (Seriola dumerili) juveniles were fed with different diets containing corn and wheat by- products. Intermediate metabolism and oxidative status were analyzed in plasma and liver, respectively. There were no significant differences between treatments in growth performance and physiological biomarkers. Therefore, the cereal by-products tested in the present study seem to be good sustainable alternatives for aquafeeds.

The study of fish digestive biochemistry is essential to understand factors that affect the net efficiency of food transformation and growth, and therefore aquaculture profitability. The aim of the present study was to assess the activity and functional characteristics of key digestive enzymes in juveniles of greater amberjack (Seriola dumerili), as well as the possible modulation of their relative importance by water temperature. For that, a combination of biochemical assays and substrate-SDS-PAGE were used. Under physiological conditions pepsin activity was negligible. Chymotrypsin was the most active enzyme in the digestive tract of the greater amberjack, while lipase was the enzyme with lower activity, though both enzymes in addition to trypsin were responsive to water temperature as revealed by discriminant analysis. Seriola dumerili showed to have pH-sensitive and, except for chymotrypsin, thermally robust proteases. Inhibition assays showed the major importance of serine proteases and revealed inverse trypsin and chymotrypsin responses to environmental temperature, with higher trypsin contribution in 26°C-fish while higher chymotrypsin contribution in 18°C-fish. Zymograms revealed three isotrypsin and three isochymotrypsin enzymes, with no variation in the presence of particular isoforms among rearing temperatures. However, they confirmed the role of chymotrypsin activity in providing digestive plasticity, with one of the isoforms being more active at lower temperatures. Thus, results indicate that variation in the relative contribution of chymotrypsin isoenzymes to a particular environmental temperature occurs due to different physic-chemical features of isoforms as a source of functional flexibility. This study assessed for the first time the effects of rearing temperature on greater amberjack digestive enzymes, increasing the knowledge on its digestive biochemistry, and aiding in the improvement of management practices for this species industrialization.

Plant-derived flours are currently being used as alternative ingredients to fishmeal in aquafeeds. However, most of them are competing for other uses, mainly as food for humans. The cereal industry generates abundant amount of residual byproducts that may represent a source of sustainable and low-cost feedstock for fish feeding, presenting limited competition with human food consumption. In this study, four different by-products derived from the cereal industrial processing has been selected and tested to assess their usefulness as potential alternative ingredients in aquafeeds. With this aim, a generalist formulation was designed in order to check those ingredients in three different European fish species (Atlantic salmon, gilthead seabream and greater amberjack). Therefore, the feed formulation was not customized for any of the targeted species. The present report shows the experiments carried out with greater amberjack (Serio/a dumerili)

Sustainable aquaculture concept involves environment, community, business and farm management practices. Efficient and viable feed uses emerge as one of the most critical issues. Reducing aquafeeds dependence on marine fish meal and oil has been a goal in European projects for 25 years. Currently, relevant proportion of these ingredients is replaced by plant-based sources. But, the increasing feed demand and the competition of plant crops for other traditional and novel uses intensify the search for sustainable sources. Envisioned solutions deal with agricultural by-products and new products produced in highly efficient system with independence on seasonal quality fluctuations. The aim of this work is the consumer’s perception of sustainable aquaculture associated with the reutilization of vegetable by-products in three European countries with a high fish consumption: Iceland, Italy and Spain. Determinants of consumer attitudes towards and spending on sustainable aquaculture products were addressed. A 17-question survey instrument was developed with input from industry and academy. The survey was designed in September 2021 and performed during October/November 2021. The effects of several covariates of interest on consumer attitudes and their willingness to pay using regression models were estimated. Results revealed that consumers who are college-educated, having largest fish consumption and more aware about the declaration of origin tend to spend more on sustainable aquaculture. Attitude indices were used as dependent variables in three distinct regressions, one for each of the countries. Differences between countries were evidenced according to preferences for different sustainability attributes. Overall, consumers from the three countries showed a positive attitude towards sustainable aquaculture. But, the need for clear labels and communication was highlighted to increase consumer acceptance and affect consumers' buying behavior. A segment of the consumers is w

• Temperature is one of the most important factors regulating the rate of many biological processes. • The study of fish digestive biochemistry is essential to obtain valuable information on factors affecting food transformation and growth, and therefore Aquaculture profitability. • The greater amberjack, Seriola dumerili, is a fast-growing pelagic teleost with great interest for the diversification of marine fish aquaculture in the Mediterranean region.

Extruded feeds are widely used for major aquatic animal production, particularly for finfish. However, the transition from fresh/frozen to extruded/ pelleted feeds remains a major obstacle to progressing sustainable farming of European lobster (Homarus gammarus). The aim of the present study was to investigate the effects of using extruded feeds with different protein levels and lipid/carbohydrate ratios on growth, feed utilisation, nucleic acid derived indices (sRD) and digestive enzymatic activity of H. gammarus juveniles. Six extruded feeds were formulated to contain two protein levels (400 and 500 g/kg), with three lipid/carbohydrate ratios (LOW – 1:3; MEDium – 1:2; HIGH – 1:1). The extruded feeds were tested against Antarctic krill (Euphausia superba) used as control (CTRL). Overall, the CTRL and 500MED feed supported the highest growth and nutritional condition estimated by means of sRD, while the poorest results were observed for the 400HIGH and 400MED groups. The FCR was significantly lower in the CTRL than all extruded feeds, among which the most efficient, i.e., lower FCR, was the 500MED. The highest activity of trypsin and amylase in lobsters fed the 400MED and 400HIGH feeds points to the activation of a mechanism to maximise nutrients assimilation. The highest lipase activity observed for the 500LOW and 500MED groups indicates a higher capacity to metabolise and store lipids. Overall, the results suggest that the 500MED feed (500 g/kg protein, 237 g/kg carbohydrates and 119 g/kg lipids) is a suitable extruded feed candidate to replace Antarctic krill, commonly used to grow lobster juveniles.