Luca Parma

The increasing global demand for sustainable seafood calls for innovative solutions that reduce reliance on marine resources. Organic aquaculture, with its focus on environmental sustainability and animal welfare, represents a promising avenue. However, one of the major constraints to its expansion is the limited availability of certified organic feed ingredients. In this study, we evaluated the feasibility of replacing fishmeal (FM) in the diets of meagre ( Argyrosomus regius ), a promising aquaculture species, by increasing the inclusion of organic pea protein meal (0%, 7%, 18% and 27.5%), while supplementing all pea‐protein enriched diets with fixed levels of functional organic ingredients (5% yeast and 2% brown seaweed). Four isoenergetic diets—C (control), PEA 7%, PEA 18% and PEA 27%—were administered to triplicate groups of 40 juvenile meagre over 85 days. We assessed growth performance, feed utilisation, body composition, plasma biochemistry, and gut microbiota composition. All pea protein inclusion levels (7%–27.5%) showed comparable growth to the control diet, with no significant differences in final body weight (PEA 7%: 173 ± 22.5 g; PEA 18%: 189 ± 11.7 g; PEA 27%: 178 ± 23.7 g vs. control: 171 ± 10.0 g) or feed conversion ratio (FCR), demonstrating successful FM replacement up to 27.5%. The PEA 18% group showed superior lipid utilisation with 109% ± 7.21% gross lipid efficiency (GLE; vs. 75.4% ± 10.8% in PEA 7% and 85.3% ± 5.47% in control) and optimal protein metabolism (albumin [ALB]: 0.71 ± 0.07 g/dL vs. control: 0.62 ± 0.05), indicating enhanced nutrient utilisation at intermediate inclusion. High pea inclusion (27.5%) significantly increased beneficial Lactobacillus (8.74% ± 3.30% vs. control: 4.92% ± 3.96%) while maintaining microbial diversity, suggesting pre‐biotic effects without dysbiosis. Overall, the results demonstrated that organic pea protein as well as organic seaweed and yeast can be successfully incorporated into meagre diets without compromising growth, feed efficiency, or fish health. These findings highlight the potential of organic pea meal as a sustainable protein alternative to FM in organic aquafeeds for meagre.

This study investigates the immunomodulatory effects of fish protein hydrolysates (FPHs) derived from Atlantic salmon ( Salmo salar ) by‐products using the Dicentrarchus labrax brain (DLB‐1) cell line. Utilizing aquaculture by‐products for FPH production offers significant potential in aquaculture, providing both economic benefits and a reduction on environmental impact. FPHs contain bioactive peptides with several biological properties, including health‐promoting, antioxidant, anti‐inflammatory, and antimicrobial activities. This study focused on the immunological properties of three FPHs, namely SS1, SS4, and SS5, obtained from salmon skin by‐products using enzymatic hydrolysis with trypsin, α chymotrypsin, and bromelain, respectively. Cytotoxicity assays showed that SS5 hydrolysate exhibited no toxic effects on DLB‐1 cells, even at high concentrations (up to 80 µg/mL), unlike SS1 and SS4 that showed a 50% cytotoxic concentration (CC ₅₀ ) of 7.0 and 11.8 µg/mL, respectively. Gene expression analysis revealed that SS1, SS4, and SS5 hydrolysates significantly upregulated the proinflammatory gene IL-1β ( p < 0.05), especially after LPS stimulation, indicating their potential to activate macrophages and modulate immune responses after bacterial infections. Interestingly, SS5 also significantly upregulated the anti‐inflammatory gene IL-10 when treated with LPS ( p < 0.05), suggesting its ability to regulate inflammation and balance immune responses. These results highlight the role of hydrolysis conditions, such as enzyme selection and peptide molecular weight, in determining the bioactivity of FPH. Moreover, the study suggests that smaller peptides with mass >1.0 and <2.0 kDa, particularly those produced with the bromelain enzyme in SS5, exhibit enhanced anti‐inflammatory properties. This research supports the use of FPH in promoting fish health by improving immune responses, and it contributes to sustainable aquaculture practices by transforming waste into valuable bioactive compounds, offering insights for future applications in functional feeds.

The microcotylid Sparicotyle chrysophrii is one of the most harmful parasites for the aquaculture of the gilthead seabream Sparus aurata, for which effective treatments are needed. The efficacy of dietary praziquantel (PZQ, 30–50 mg kg body weight⁻¹ day⁻¹), emamectin benzoate (EMB, 0.015–0.050 mg kg BW⁻¹ day⁻¹), and fenbendazole (FBZ, 40–75 mg kg BW⁻¹ day⁻¹) against S. chrysophrii on gilthead seabream was tested in four different in vivo challenge trials. Specimens of gilthead seabream naturally infected with S. chrysophrii were maintained in three separate recirculating aquaculture systems of 142 L (1 control vs. 2 treated). Fish were fed (ration 1.2% BW day⁻¹) 5 days a week for 4 weeks, alternating weeks with medicated and control feed. On days 0, 14, and 28, samples of 7–9 fish per group were collected and the gills were examined for S. chrysophrii. The gills of hosts treated with EMB and FBZ were evaluated by histopathology. The trials showed that in‐feed PZQ has low palatability, causing rejection which did not allow its efficacy to be adequately investigated. While dietary EMB was associated with adverse effects, such as gill de‐epithelialisation and necrosis, with no demonstrated efficacy against S. chrysophrii. On the other hand, all the fish treated with FBZ lost all parasites, showing 100% efficacy and also suggesting a preventive/repellent action against the monogenean. In conclusion, the present study provides indications for the use of dietary FBZ as a medical device for the treatment/prophylaxis of sparicotylosis in aquaculture.

The present study was designed to evaluate the effects of dietary levels of bioactive peptides (BPs) derived from salmon processing by-products on the presence and distribution of peptic cells (oxyntopeptic cells, OPs) and enteric endocrine cells (EECs) that contain GHR, NPY and SOM in the gastric mucosa of European seabass and gilthead seabream. In this study, 27 seabass and 27 seabreams were divided into three experimental groups: a control group (CTR) fed a control diet and two groups fed different levels of BP to replace fishmeal: 5% BP (BP5%) and 10% BP (BP10%). The stomach of each fish was sampled and processed for immunohistochemistry. Some SOM, NPY and GHR-IR cells exhibited alternating “open type” and “closed type” EECs morphologies. The BP10% group (16.8 ± 7.5) showed an increase in the number of NPY-IR cells compared to CTR (CTR 8.5 ± 4.8) and BP5% (BP10% vs. CTR p ≤ 0.01; BP10% vs. BP5% p ≤ 0.05) in the seabream gastric mucosa. In addition, in seabream gastric tissue, SOM-IR cells in the BP 10% diet (16.8 ± 3.5) were different from those in CTR (12.5 ± 5) (CTR vs. BP 10% p ≤ 0.05) and BP 5% (12.9 ± 2.5) (BP 5% vs. BP 10% p ≤ 0.01). EEC SOM-IR cells increased at 10% BP (5.3 ± 0.7) compared to 5% BP (4.4 ± 0.8) (5% BP vs. 10% BP p ≤ 0.05) in seabass. The results obtained may provide a good basis for a better understanding of the potential of salmon BPs as feed ingredients for seabass and seabream.

In recent years, insect meal has attracted increasing interest as an innovative protein source to replace fish meal in feed formulation due to its valuable nutritional profile. This research aimed to compare the effects of different dietary inclusion levels (5, 10, and 15%) of Hermetia illucens (HI) larvae meal on Sparus aurata (initial weight: 98.6 ± 0.6 g) sensorial, technological, and nutritional fillets quality. Fish were fed experimental diets over 113 days. Results showed that the inclusion of defatted HI larvae meal did not induce off-flavours in gilthead sea bream fillets. No significant differences were found in appearance, mouthfeels, and texture, while a difference emerged in the trait ‘cooked chicken breast’ for odour and flavour characteristics. Moreover, fillets’ quality traits and proximate composition analyses performed did not show significant differences between the treatments. The fillets’ fatty acid content showed that higher inclusion of HI meal leads to higher saturated fatty acids content, while no significant difference in polyunsaturated fatty acids was observed among treatments. Results have a positive implication as dietary HI did not negatively affect the fatty acids composition or quality of sea bream fillets.

The aim of the present study was to evaluate the effects on the presence and distribution of oxyntopeptic cells (OPs) and enteroendocrine cells (EECs) expressing GHR, NPY and SOM in the gastric mucosa of European seabass and seabream of dietary levels of bioactive peptides (BPs) obtained from salmon processing by-products (in silico approach). In this study, 27 seabass and 27 seabreams were divided into three experimental groups: a control group (CTR) fed a control diet and two groups fed different levels of BP to replace fishmeal: 5% BP (BP5%) and 10% BP (BP10%). The stomach of each fish was sampled and processed for immunohistochemistry. Some SOM, NPY and GHR-IR cells exhibited alternating “open type” and “closed type” EECs morphologies. In seabream gastric mucosa, the BP10% group (16.8 ± 7.5) showed a significant change in NPY-IR cell number compared to CTR (CTR 8.5 ± 4.8) and BP5% (BP10% vs. CTR P ≤ 0.01; BP10% vs. BP5% P ≤ 0.05). In seabream, SOM-IR cells in the BP 10% diet (16.8 ± 3.5) differed from those in CTR (12.5 ± 5) (CTR vs. BP 10% P ≤ 0.05) and BP 5% (12.9 ± 2.5) (BP 5% vs. BP 10% P ≤ 0.01). In seabass, EEC SOM-IR cells increased at 10 % BP (5.3 ± 0.7) compared to 5 % BP (4.4 ± 0.8) (5 % BP vs. 10 % BP P ≤ 0.05). The results obtained suggest that salmon BPs have a promising impact as circulating ingredients for seabass and seabream.

Nowadays functional ingredients have a significant potential for improving current low fish meal (FM) aquafeed formulation in sustaining growth and enhancing animal robustness for Mediterranean aquaculture. Among them, nucleotides (NT) and nucleic acids (NA) drew attention for their application in the last two decades. NT are organic molecules involved in many life-supporting pathways, and are the building blocks of NA, which stand as genetic repositories. NT are naturally present in organic ingredients, and among them FM is known to be one of the highest NT sources. When this NT source is seriously limited, fish might be under the minimum NT requirements, especially in fast growing life stages of carnivorous species. Hence, a trial on European sea bass juveniles was carried out, testing two dietary FM levels (FM10, FM20 as 10% and 20% FM, respectively) supplemented with 500 mg kg^-1 yeast-originate NT or NA dose over 80 days. Thereafter, fish were exposed to one week of sub-optimal thermal and dissolved oxygen condition (30°C and 4.0 mg/L O₂) to further explore the effect of NT and NA inclusion on immune response and gut microbiome alteration. At the end of the growth period NT increased feed intake at both FM dietary levels. FM20 combined with NA and NT further improved growth performance, enhancing lipid efficiency and increased anti-inflammatory TGF-β. After sub-optimal environmental conditions both NT and NA exerted prebiotic functions on gut microbiome by promoting beneficial lactic acid bacteria such as Weissella and Leuconostoc. At the same time NT in 10% FM diet increased the abundance of Bacillus taxon. In conclusion, the combination of NT/NA included at 500 mg kg^-1 was able to promote growth when included in 20% FM level, assuming higher nutritional NT requirement when combined with 10% FM. On the other hand, NT/NA added in 10% FM upregulate proinflammatory IL-1β and favor beneficial gut bacterial taxa.

To provide practical feeding management guidelines preceding a stressful episode during farming practices, European sea bass juveniles (initial weight: 72.3 g) were fed for 60-days different fish meal (FM) and fish oil (FO) dietary levels [high (30% FM, 15% FO, FM30/FO15), intermediate (20% FM, 7% FO, FM20/FO7), and low (10% FM, 3% FO, FM10/FO3)] in triplicate conditions. Fish were then fasted for 36 h and exposed to a 2-h acute crowding (80 kg m^–3 biomass). Plasma biochemistry, skin mucus parameters and gene expression of stress and immune-related genes were performed before, at 2 and 24 h after crowding. At the end of the trial, the FM10/FO3 group showed lower final body weight, weight gain, and specific growth rate compared to the other treatments. Most of the plasma parameters were mainly affected by crowding condition rather than diet; however, after stress, lactate was higher in the FM30/FO15 group compared to the other treatments. Similarly, protease, antiprotease, peroxidase and lysozyme in skin mucus were mostly affected by crowding conditions, while fish fed FM10/FO3 displayed higher skin mucosal IgM and bactericidal activity against Vibrio anguillarum and V. harveyi. Most of the stress-related genes considered (hsp70 and gr-1 in the brain; hsp70, gr-1 and gr-2 in the head kidney), showed an overall expression pattern that increased over time after stress, in addition, hsp70 in the head kidney was also up-regulated in fish fed FM30/FO15 after stress. Higher plasmatic lactate together with the up-regulation of some stress-related transcripts suggest a higher reactivity to acute crowding of the stress-response mechanism in fish fed high FM and FO dietary levels. Otherwise, the higher skin mucosal IgM and bactericidal activity observed in fish fed FM10/FO3 dietary levels seems to indicate that acute crowding was able to activate a higher pro-inflammatory response in this treatment. Overall, the results of the present study seem to indicate that 10% FM and 3% FO dietary levels might affect stress and immune responses.

The current work was designed to assess the effect of feed supplemented with essential oils (EOs) on the histological features in sea bass’s gastric mucosa. Fish were fed three diets: control diet (CTR), HERBAL MIX^® made with natural EOs (N-EOs), or HERBAL MIX^® made with artificial EOs obtained by synthesis (S-EOs) during a 117-day feeding trial. Thereafter, the oxyntopeptic cells (OPs) and the ghrelin (GHR) and somatostatin (SOM) enteroendocrine cells (EECs) in the gastric mucosa were evaluated. The Na⁺K⁺-ATPase antibody was used to label OPs, while, for the EECs, anti-SOM and anti-GHR antibody were used. The highest density of OP immunoreactive (IR) area was in the CTR group (0.66 mm² ± 0.1). The OP-IR area was reduced in the N-EO diet group (0.22 mm² ± 1; CTR vs. N-EOs, p < 0.005), while in the S-EO diet group (0.39 mm² ± 1) a trend was observed. We observed an increase of the number of SOM-IR cells in the N-EO diet (15.6 ± 4.2) compared to that in the CTR (11.8 ± 3.7) (N-EOs vs. CTR; p < 0.05), but not in the S-EOs diet. These observations will provide a basis to advance current knowledge on the anatomy and digestive physiology of this species in relation to pro-heath feeds.

A 121-day feeding trial was undertaken to test the effects of two dietary lipid levels (16 and 21% L16, L21) in triplicated gilthead sea bream groups (initial weight: 67.5 g) reared at two different water temperatures (high, H 23°C and low, L 17°C) in the same recirculation system but exposed to a switch in temperature after 58 days. Fish kept at H were transferred to L (HL transition, autumn shift), and the fish kept at L were exposed to H (LH transition, summer shift), while continuing to receive the same diet to apparent satiation in each group. At the end of the trial, no significant diet effect on specific growth rate (SGR), feed intake (FI), and feed conversion rate (FCR) were detected in fish exposed to HL transition compared with those exposed to LH transition, while gross lipid efficiency (GLE) and lipid efficiency ratio (LER) were higher in L16. After temperature changes, L16 displayed higher SGR, FI, GLE, and LER, while mesenteric fat index was reduced. After temperature changes, the combined effects of low lipid diet and low temperature conditions resulted in higher pepsin activity, while trypsin, chymotrypsin, and lipase activities were generally higher at high lipid content. The combined effect of diet and temperature did not alter the metabolic plasma profile, except for the observed final higher aspartate aminotransferase (AST) and alkaline phosphatase (ALP) values when combining high dietary lipid (L21) and temperature changes. Different diets showed a significantly different gut microbiome layout, only at high temperature with L16 diet resulting in a higher load of Lactobacillus. On the contrary, no dietary impact on ecosystem diversity was observed, independently from the temperature. In addition, L16 diet in the HL transition favored an increase in Weissella and Bradyrhizobium genera in the gut microbiome, while in the final condition of LH transition, L21 diet favored a significant increase in Streptococcus and Bacillus. According to the results, the utilization of 16% dietary lipid levels in gilthead sea bream should be preferred during seasonal temperature changes in order to optimize feed utilization and gut health.