Optimization of feeding quantity and frequency to rear the cyprinid fish Garra rufa (Heckel, 1843)

Garra rufa has a high commercial value, but their rearing methods are still unknown. Aspects like an adequate daily dose and feeding frequency need to be investigated. This work aimed to establish the optimal feed dose per day to obtain satiation and the optimal frequency of feeding to rear a specific size class of G. rufa. A total of 60 fish were distributed by six aquaria containing 10 fish. First, the fish were fed twice per day, by providing a feed dose correspondent to 1% of their body weight and increasing 0.1 g/fish on the following days, until finding feed leftovers on the next morning. Afterwards, the fish went through a 1 month experimental trial to evaluate the optimal feeding frequency. Fish growth was compared between feeding the optimal daily dose distributed in two or three feeding moments per day. The optimal dose that ensured satiation was 0.042 g fish^?1 day^?1 (3.2% of fish’ body weight). Feeding the fish three times per day promoted higher growth rates, since the fish’ total length was statistically different between feeding frequencies. Statistically significant differences between feeding frequencies were not observed for growth performance parameters. These results contribute to the aquaculture of this target species, allowing fish industry to more efficiently respond to the high demand for G. rufa and, simultaneously, for its preservation in the wild.     

Virulence‐associated factors in Vibrio cholerae non‐O1/non‐O139 and V. mimicus strains isolated in ornamental fish species

During recent decades, ornamental fish have proven to be one of the fastest growing categories of pets in Europe. In this framework, we evaluated both the potential pathogenic and zoonotic risks caused by 53 Vibrio cholerae non‐O1/non‐O139 and a Vibrio mimicus strain isolated from ornamental fish species mostly originating from South‐East Asia countries between 2000 and 2015 in Italy. All the strains were firstly identified at species level by biochemical, phylogenetic and mass spectrometry (matrix‐assisted laser desorption ionization time of flight) methods, and then studied to reveal the presence of the main virulence and colonization‐associated factors, as ctxA, ace, zot, stn/sto, toxR, rtxA, hlyA and tcpA by multiplex and single endpoint PCR assays. Findings showed that 21 of 54 strains harboured at least one virulence factor with a predominance for the toxR⁺, rtxA⁺ and hlyAET⁺ genotype. Interestingly, the V. mimicus strain harboured the colonization factor and the CTX prophage receptor, tcpA, indicating the ability to capture and integrate it in its genome increasing its pathogenicity. Although these enterotoxins can sporadically cause gastroenteritis, the results highlight their probable involvement in causing severe implications for public health, suggesting the need for an European microbiological monitoring.     

Selection of lactic acid bacteria as candidate probiotics for Vibrio parahaemolyticus depuration in pacific oysters (Crassostrea gigas)

The application of probiotics in food is now widespread and is widely accepted by consumers. Lactic Acid Bacteria (LAB) were isolated from traditional salted fish and then characterized by its ability to inhibit Vibrio parahaemolyticus growth using minimal inhibitory concentration tests. Five out of these strains were identified as Lactobacillus delbrueckii, Lactobacillus casei and three Lactobacillus gasseri by PCR using 16S and 23S rRNA genes. Antibiofilm activity of Lactobacillus spp. extracts were also tested in 96 polystyrene plates. A potential antibiofilm effect was demonstrated as most LAB. Although most LAB extract were able to eradicate pre‐formed biofilm, results demonstrated that five Lactobacillus spp. exhibited a stronger inhibitory effect against V. parahaemolyticus in infected oysters. Vibrio parahaemolyticus viable cells number declined from 10⁶ UFC to 10⁴ UFC after 3 days of incubation with Lactobacillus spp. Probiotic applications, in biological control of seafood associated pathogens can be an alternative solution, providing consumer with a product of good quality owing to the use of non‐toxic compounds. Based on our results, LAB could be used as a bioprotective culture in oyster's depuration to prevent V. parahaemolyticus growth.     

An evaluation of fish health‐management practices and occupational health hazards associated with Pangasius catfish (Pangasianodon hypophthalmus) aquaculture in the Mekong Delta,Vietnam

This study aimed to evaluate the current status on the use of probiotics, disinfectants and antimicrobials in hatcheries, nurseries and grow‐out farms producing Pangasius catfish (Pangasianodon hypophthalmus) in the Mekong Delta, Vietnam. Semi‐structured interviews were conducted with 83 aquaculture enterprises (15 hatcheries, 32 nurseries and 36 grow‐out farms). Farmers reported use of a total of 24 different antimicrobials, e.g. for treatment of bacillary necrosis and motile aeromonad septicaemia, and a variety of disinfectants, probiotics and nutritional supplements. In contrast to small‐scale farmers, all large‐scale grow‐out farmers studied were certified and therefore had higher levels of formal education and specialized aquaculture training to diagnose and treat diseases. All farmers prepared their own medicated feed with a high risk of treatment failure, negative environmental impact from released antimicrobials and resistance development. Small‐scale farmers were at particular occupational health risks when handling antimicrobials and other chemicals, e.g. mixing medicated feed with bare hands. There is an urgent need to improve knowledge and use innovative approaches, e.g. private‐public partnerships, to assure a prudent use of chemicals, to improve capacity and access to disease diagnosis, particularly for small‐scale grow‐out farmers and nurseries. Efforts to control use of antimicrobials in aquaculture should be coordinated with the livestock and human health sectors taking an One‐Health approach.     

Antagonism against fish pathogens by cellular components and verification of probiotic properties in autochthonous bacteria isolated from the gut of an Indian major carp,Catla catla (Hamilton)

Probiotic potential of the autochthonous bacteria in catla, Catla catla has been evaluated through determination of antagonistic activity (in vitro) of the cellular components of gut bacteria against seven fish pathogens. Altogether 208 strains were isolated, inhibitory activity of the isolates was evaluated through cross‐streaking and 16 primarily selected antagonistic strains were confirmed using the double‐layer method. Four bacteria that showed antagonism against ≥4 pathogens were selected as putative probiotics. The intracellular, extracellular, whole‐cell and heat‐killed cell components exhibited bactericidal activity against the pathogens. In addition, the selected strains were capable of producing different extracellular enzymes, competent to grow in intestinal mucus and could tolerate diluted bile juice. Analysis of 16SrRNA partial gene sequence revealed that both the strains CC1FG2 and CC1FG4 were Bacillus methylotrophicus (KF559344 and KF559345), while the isolates CC1HG5 and CC2HG7 were Bacillus subtilis subsp. spizizenii (KF559346) and Enterobacter hormaechei (KF559347) respectively. Bio‐safety evaluation through intra‐peritoneal injection of the isolates did not induce any pathological signs or mortalities in C. catla. The study confirmed probiotic properties of autochthonous gut bacteria in C. catla and demonstrated potential for using them as bio‐control agents. However, in vivo studies are essential to explore their efficacy in the commercial aquaculture.     

Bioassay‐guided isolation and identification of active compounds from Macleaya microcarpa (Maxim) Fedde against fish pathogenic bacteria

Four alkaloids (Sanguinarine, 6‐Methoxyl‐dihydro‐chelerythrine, Cryptopine and β‐Allocryptopine) were isolated from aerial parts of Macleaya microcarpa (Maxim) Fedde using bioassay‐guided isolation method, and the inhibitory activity of ethanolic extract, various fractions and these four alkaloids against four fish pathogenic bacteria (Aeromonas hydrophila, Aeromonas salmonicida, Vibrio anguillarum and Vibrio harveyi) was assessed in vitro using the agar dilution method and the microdilution assay method respectively. A. hydrophila was the most sensitive strain to all the tested compounds. Minimum inhibitory concentration (MIC) values were lower for sanguinarine against all tested Gram‐negative strains than other three alkaloids, with MIC values of 12.5 mg L^?1 for A. hydrophila and 50 mg L^?1 to other pathogenic bacteria. Followed by 6‐methoxyl‐dihydro‐chelerythrine, which showed considerable antibacterial activity with MIC values of 80 mg L^?1 for A. hydrophila, 100 mg L^?1 for V. harveyi, and 125 mg L^?1 for both V. anguillarum and A. salmonicida. Cryptopine and β‐allocryptopine revealed similar inhibitory activity with MIC values of 100 mg L^?1 for A. hydrophila and 200 mg L^?1 for other three bacterial species. These finding provided evidence that extract, as well as isolated compounds from M. microcarpa might be potential sources novel antibacterial agents for the treatment of fish infectious diseases.     

High prevalence of antimicrobial resistance in Escherichia coli,Salmonella spp. and Staphylococcus aureus isolated from fish samples in India

Antibiotic resistance, driven by inappropriate use of antimicrobial agents for fish farming, is an expanding global health threat. Demand of animal protein for human consumption is entraining at remarkable pace which in turn, upturning the non‐judicial use of life‐saving drugs in these modern animal production practices at an incautious rate. Hence, study was devised to observe the antimicrobial resistance (AMR) pattern of human prominence bacteria, against drugs of critically and highly importance of both human and veterinary medicine, circulating over the fish farming in India. One hundred sixty fish faecal samples were obtained from distinct geographical locales of Rajasthan, India. Overall, 202 isolates comprising of Escherichia coli (81, 51%), Salmonella spp. (72, 45%) and Staphylococcus aureus (49, 31%) were isolated to screen for resistance. Antimicrobial resistance has been analysed using broth microdilution method. In case of E. coli and Salmonella spp., highest resistance (>95%) was observed against streptomycin while for S. aureus, it was observed against trimethoprim, along with high resistance to other antibiotics. Majority of the isolates were found to be resistant to more than three antibiotics implying multi‐drug resistance (>89%) relative to the critical and highly important antibiotics. The high AMR is a reflection of misuse of these agents in the fish farming, which is a concern of serious health issues. Our findings persuade the prudent use of antimicrobial agents in fish farming and other aquaculture settings that may assist in drafting of the new policies for the judicial use of these life‐saving drugs in these sectors.     

Molecular characterization and interactome analysis of aerolysin (aer) gene from fish pathogen Aeromonas veronii: The pathogenicity inferred from sequence divergence and linked to histidine kinase (cheA)

Aerolysin (aer) is one of the most important and abundant virulence factors in the infection of fish by Aeromonas veronii. A comprehensive study on the molecular characterization and pathogenicity of the aer gene from 34 A. veronii isolates from diseased carp and catfish was carried out and its interactome was analysed to observe the functional correlations between aer and other proteins within the A. veronii network. The PCR‐based amplification of aer from the 34 isolates of A. veronii showed more aer‐positive isolates from catfish with a high pathogenic potential in the in vivo challenge test than the carp fish. The analysis of aer gene sequence from challenged fish revealed significant sequence divergence according to the types and geographical distribution of the fish. The networking analysis of aer from the model A. veronii B565 revealed histidine kinase (cheA) as the most functional interacting partner. The study of the interaction between aer from the experimental A. veronii and cheA demonstrated that the A chain of cheA plays a more important role than the corresponding B chain during contact, and a linker sequence of 15 residues controlled the entire interaction process. Therefore, cheA could be an excellent drug target for controlling A. veronii infection of fish.     

PCR survey for Paramoeba perurans in fauna,environmental samples and fish associated with marine farming sites for Atlantic salmon (Salmo salar L.)

Amoebic gill disease (AGD) caused by the amoeba Paramoeba perurans is an increasing problem in Atlantic salmon aquaculture. In the present PCR survey, the focus was to identify reservoir species or environmental samples where P. perurans could be present throughout the year, regardless of the infection status in farmed Atlantic salmon. A total of 1200 samples were collected at or in the proximity to farming sites with AGD, or with history of AGD, and analysed for the presence of P. perurans. No results supported biofouling organisms, salmon lice, biofilm or sediment to maintain P. perurans. However, during clinical AGD in Atlantic salmon, the amoeba were detected in several samples, including water, biofilm, plankton, several filter feeders and wild fish. It is likely that some of these samples were positive as a result of the continuous exposure through water. Positive wild fish may contribute to the spread of P. perurans. Cleaner fish tested positive for P. perurans when salmon tested negative, indicating that they may withhold the amoeba longer than salmon. The results demonstrate the high infection pressure produced from an AGD‐afflicted Atlantic salmon population and thus the importance of early intervention to reduce infection pressure and horizontal spread of P. perurans within farms.     

A bacterium with close genetic identity to Pseudomonas mandelii associated with spring fish kills in wild bluegill Lepomis macrochirus Rafinesque and pumpkinseed sunfish Lepomis gibbosus (Linnaeus)

Pseudomonas fluorescens are known bacterial pathogens in fish. The P. fluorescens group contains at least nine different bacterial species, although species from fish have rarely been differentiated. Two isolated fish kills affecting wild bluegills, Lepomis macrochirus Rafinesque, and pumpkinseed sunfish, Lepomis gibbosus (Linnaeus), occurred in the spring of 2015 during cool water temperatures (12.5°C–15.5°C). Disease signs included severe bacteraemia with rare gross external signs. Pure bacterial cultures isolated from kidneys of all affected fish were identified as P. fluorescens using the API 20NE system, while no bacteria were isolated from asymptomatic fish. To further identify the species of bacterium within the P. fluorescens complex, genetic analysis of the 16S rRNA, rpoD and gyrB genes was conducted. DNA sequences of bacterial isolates from both mortality events were identical and had close identity (≥99.7%) to Pseudomonas mandelii. Although likely widespread in the aquatic environment, this is the first report of a bacterium closely resembling P. mandelii infecting and causing disease in fish. The bacterium grew at temperatures between 5°C and 30°C, but not at 37°C. It is possible that infections in fish were a result of immunosuppression associated with spring conditions combined with the psychrotrophic nature of the bacterium.     

Replacement of fish oil with a DHA‐rich Schizochytrium meal on growth performance,activities of digestive enzyme and fatty acid profile of Pacific white shrimp (Litopenaeus vannamei) larvae

This trial was conducted to evaluate the effects of replacing dietary fish oil with Schizochytrium meal for Pacific white shrimp (Litopenaeus vannamei) larvae (initial body weight 4.21 ± 0.10 mg). Six test microdiets were formulated using Schizochytrium meal to replace 0 g/kg, 250 g/kg, 500 g/kg, 750 g/kg, 1000 g/kg or 1500 g/kg fish oil DHA. No significant differences were observed in survival, growth, final body length and activities of digestive enzyme among shrimp fed different diets (p > .05). No significant differences were observed in C20:5n‐3 (EPA) in muscle samples (p > .05). C18:3n‐3 and C20:4n‐6 in muscle increased as Schizochytrium meal replacement level increased (p < .05). No significant differences were observed in C22:6n‐3 (DHA) and n‐3 fatty acids among shrimp fed diets that algae meal replaced 0 g/kg ‐ 1000 g/kg of fish oil. Shrimp fed diet R150 had higher DHA content than other groups and had higher n‐3 fatty acids than that of shrimp fed diets R50, R75 and R100 (p < .05). C18:2n‐6, PUFA and n‐6 fatty acids in muscle increased, while n‐3/n‐6 ratio decreased with increasing algae meal replacement level from 0 g/kg to 1000 g/kg (p < .05). In conclusion, Schizochytrium meal could replace 1500 g/kg fish oil DHA in the microdiets without negatively affecting shrimp larvae survival, growth and activities of digestive enzyme.     

Recovery of Bacillus mycoides,B. pseudomycoides and Aeromonas hydrophila from common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) with gill disease

During a 3‐month period from June to the end of August 2016, ~5% mortalities were observed in a farm with rainbow trout (Oncorhynchus mykiss Walbaum) and one farm of common carp (Cyprinus carpio L.) in Bulgaria. The disease was manifested by gill ulcers/rot, asphyxiation and bloody ascites. Aeromonas hydrophila was isolated from the internal organs of all the diseased fish. Bacillus mycoides or B. pseudomycoides were recovered from the gill lesions on diseased carp and rainbow trout, respectively, with identification achieved by conventional phenotyping and by sequencing of the 16S rRNA gene. In vivo experiments confirmed that all three organisms were pathogenic to rainbow trout.     

Identification and pathogenicity study of emerging fish pathogens Acinetobacter junii and Acinetobacter pittii recovered from a disease outbreak in Labeo catla (Hamilton, 1822) and Hypophthalmichthys molitrix (Valenciennes, 1844) of freshwater wetland in West Bengal,India

The disease outbreaks in aquaculture system of wetlands are the major cause of fish mortality. Among various bacterial septicaemic diseases, fish mortality caused by Acinetobacter spp. is recently reported in different fish species. Fish disease outbreak was investigated in a wetland of West Bengal, India to identify the aetiological factors involved. The moribund fish were examined and subjected to bacterial isolation. Two bacterial causative agents were identified as Acinetobacter junii and Acinetobacter pittii by biochemical characterization and 16S rRNA gene amplification. Both the isolates were oxidase‐negative, nitrate‐negative, catalase‐positive and indole‐negative. The molecular identification using 16S rRNA gene sequencing and phylogenetic tree analysis further confirmed the two Acinetobacter spp. with 97%–99% similarity. The antibiotic resistance patterns of these two bacteria revealed that both of them were resistant to β‐lactam, cefalexin, cephalothin, amoxyclav, cefuroxime, cefadroxil, clindamycin, vancomycin and penicillin. In addition, A. pittii was also resistant to other antibiotics of cephams group such as ceftazidime and cefotaxime. In the challenge experiment, both A. junii and A. pittii were found to be pathogenic with LD₅₀ of 1.24 × 10⁵ and 1.88 × 10⁷ cfu/fish respectively. Histopathological examination of gill, liver and kidney revealed prominent changes supporting bacterial septicaemia. The investigation reports for the first time on concurrent infection by A. junii and multidrug‐resistant (MDR)‐A. pittii as emerging fish pathogens to cause severe mortality in Labeo catla and Hypophthalmichthys molitrix in a freshwater wetland.     

Growth and economic analysis of freshwater prawn,Macrobrachium rosenbergii (de Man), produced with feeds substituting sunflower cake for fish meal,soya bean meal and mustard oil cake

A feeding trial with Macrobrachium rosenbergii was carried out to test the effectiveness of sunflower cake (SFC) as a replacement for conventional protein sources. Four isonitrogenous (~30% crude protein) and isocaloric (388–402 kcal) diets were formulated. Diet‐1 was a control made with conventional ingredients including fish meal, soya bean meal and mustard oil cake. Diet‐2, Diet‐3 and Diet‐4 were made with 30%, 40% and 50% SFC, respectively, replacing the usual protein sources used in Diet‐1. After 100 days, diets with SFC inclusion showed favourable growth and economic performance trends compared to control diet‐1, but without significant differences (p > .05). Better production (572.89 ± 62.99 kg/ha) was observed with Diet‐4 followed by Diet‐2, Diet‐3 and Diet‐1. Diet‐4 revealed the best feed conversion ratio (2.56 ± 0.24), specific growth rate (1.18 ± 0.05) and protein efficiency ratio (1.14 ± 0.10) among these diets. Whole carcass composition analysis revealed highest crude protein (18.19%) and lipid (4.43%) content in prawns fed Diet‐3 followed by Diet‐4. Highest total income, gross margin and benefit cost ratio (BCR) per hectare from prawns were US$5,759, US$2,623 and 1.84, respectively, found in Diet‐4. This study demonstrates that 30%–50% inclusion of SFC has favourable impacts on productivity and profitability compared with controls, with 50% SFC inclusion as the most cost‐effective diet for prawns without apparent compromise in growth, flesh quality or economics. The performances of the diets suggest that SFC may be a suitable substitute for fishmeal, soya bean meal and mustard oil cake in prawn feed. The effectiveness of higher SFC concentrations should also be investigated.     

The role of polychaete Nereis diversicolor in bioremediation of wastewater and its growth performance and fatty acid composition in an integrated culture system with Huso huso (Linnaeus, 1758)

This study was undertaken to evaluate the role of polychaete Nereis diversicolor in bioremediation of waste water and its growth performance and fatty acid composition in an integrated culture system with great sturgeon, Huso huso. Three treatments consisting of N. diversicolor fed with H. huso waste (FNW), N. diversicolor fed with fish feed waste (NW), and fish waste without the worm (FW) were considered at water temperature of 23°C for 8 weeks. The obtained results demonstrated that N. diversicolor in the flow‐through system could grow via feeding with the fish waste water. The pure production and survival rate of harvested Nereis in NW treatment were significantly higher than those of FNW treatment (p < .05). However, no significant difference was observed in specific growth rate and weight gain between these two treatments (p > .05). The highest removal efficiency of waste water including total nitrogen (56%), total phosphorus (53%), NO₂‐N (91%), NH₃‐N (35%)_, PO₄‐P (47%), BOD₅ (60%) were seen in FNW treatment. Also, the highest additional efficiency of NO₃‐N occurred in FW (37%) treatment. Certain fatty acids specifically 20:5 ω3 (eicosapentaenoic acid [EPA]) and 22:6 ω6 (docosahexaenoic acid [DHA]) were also abundant in Nereis, and analysis revealed some differences due to the diet. These results demonstrated that the promotion of growth by cultured Nereis can enhance the decomposition rate of organic matter in enriched sediment and minimize negative effects in fish farms. These results also suggest that the use of N. diversicolor is an excellent potential candidate for an integrated aquaculture and nutrient recycling including the removal of organic wastes.     

The effect of photoperiod and feeding frequency on larval of the Amazonian ornamental fish Pyrrhulina brevis (Steindachner, 1876)

This study aimed to evaluate the performance of Pyrrhulina larvae, Pyrrhulina brevis, under different photoperiods and feeding frequencies. A completely randomized design was used, with four replicates in a 5 × 2 factorial, with five photoperiods (6L:18D, 12L:12D, 16L:8D, 20L:4D, 24L:0D) and two feeding frequencies (two or four times a day). Four hundred larvae with an initial length of 4.6 ± 0.09 mm were randomly distributed in 40, 1‐L containers at a density of 10 larvae/L. Feeding was performed with Artemia nauplii in the ratio of 150 Artemia nauplii/larva/feeding. After 15 days, all larvae were euthanized for measurements of length (mm), final weight (mg), survival rate (%) and larvae uniformity in weight an length (%). The data were subjected to analysis of variance and subsequently, in case of significance, a Tukey test was performed to compare means. There was no interaction between photoperiod and feeding frequency on studied variables (P > 0.05). Likewise, there was no influence of feed rate on the same variables (P > 0.05). There was only influence of photoperiod, where the larvae subjected to longest photoperiods (24L:0D and 20L:4D) showed improved weight and length (P < 0.05). Therefore, a photoperiod of 20L:4E, with feeding twice a day is recommended.     

Chemical,bioactive properties and in vitro digestibility of spray‐dried fish silages: Comparison of two discard fish (Equulites klunzingeri and Carassius gibelio) silages

The fermented fish silages produced with Streptococcus spp., Lactobacillus brevis, Lactobacillus plantarum, Pediococcus acidilactici and Enterococcus gallinarum, and formic acid silages were compared for production of two discard fish silages (Equulites klunzingeri and Carassius gibelio). The E/NE ratio of spray‐dried fish silages was determined in range of 0.80–1.10 for E. klunzingeri and 0.80–0.90 for C. gibelio silages. Pediococcus acidilactici and En. gallinarum groups had greater antioxidant activity than other silage groups. The DPPH radical scavenging ability was found as 6.14%–14.71% and 6.99%–13.36% for E. klunzingeri and C. gibelio silages, respectively. The OMD, ME and NE_L values were determined in range of 69.74%–80.08%, 6.38–8.65 MJ/kg DM and 6.45–7.49 MJ/kg DM, respectively for spray‐dried E. klunzingeri silages and 81.18%–86.62%, 8.97–9.61 MJ/kg DM and 7.61–8.08 MJ/kg DM, respectively, for spray‐dried C. gibelio silages. According to the nutritional and chemical evaluation, spray‐dried fish silages have great potential as a feed components because of high rate of digestibility and nutritious components.     

Utilization of diets with different fish oil content in common octopus (Octopus vulgaris Cuvier, 1797) and resulting changes in its biochemical composition

The aim of the present work was to obtain the lipid utilization of Octopus vulgaris supplying formulated semi‐moist diets with different contents in cod oil (reduced from water content): 0 g kg^?1 (A0, 138 g kg^?1 lipids DW; N = 4), 100 g kg^?1 (A100, 286 g kg^?1 lipids DW; N = 6) and 200 g kg^?1 (A200, 388 g kg^?1 lipids DW; N = 6). The rest of the ingredients were constant in the three diets: 200 g kg^?1 gelatin, 100 g kg^?1 egg yolk powder, 150 g kg^?1 freeze‐dried Todarodes sagittatus and 50 g kg^?1 freeze‐dried Sardinella aurita). Survival was 100% with the three diets. The highest absolute feeding (15.8 ± 1.2 g day^?1), growth (9.6 ± 1.4 g day^?1; 0.91% BW day^?1) and feed efficiency rates (60.3%) were obtained with diet A0. This diet also showed greater retention of lipid and protein than A100 and A200. Protein digestibility was above 95% in all of the diets. Only diet A0 led to a high lipid digestibility coefficient (81.25%), which fell drastically to 12.3% in A200. It was notable the high polar lipid digestibility rates (83–89%) respect to neutral lipids (2–87%) in all diets. The best results were obtained with lipid feeding rates of around 1 g day^?1 and a suitable lipid content on 130–140 g kg^?1 DW in formulated diets for O. vulgaris.