Juvenile Grouper Research Articles

Polystyrene nanoplastics affect digestive function and growth in juvenile groupers

Polystyrene nanoplastics (PS-NPs) can impair antioxidant, immune, and nervous system functions as well as growth and development in aquatic organisms. At present, however, little is known about the effects and underlying mechanisms of PS-NPs on the digestive system of marine fish. Here, we studied the effects of these plastics on the intestinal health and growth performance of juvenile orange-spotted groupers (Epinephelus coioides). Based on histopathological analysis, we found that the liver and intestines can uptake PS-NPs at exposure concentrations of 300 and 3000 μg/ml, respectively. After 14 d of exposure, the activities of digestive enzymes lipase (LPS), trypsin (TRS), and lysozyme (LZM) were reduced, indicating that PS-NPs negatively affected digestive function in juvenile groupers. The PS-NPs also altered microbial community composition, resulting in a decrease in diversity and simplification of network relationships in the intestinal microbiota, but a significant increase in certain harmful bacteria, especially Vibrio and Aliivibrio. In addition, community assembly changed from being driven primarily by deterministic processes (68.89% for control group) to stochastic processes (73.33% and 51.11% for 300 and 3000 μg/ml PS-NP exposure groups, respectively). Furthermore, the specific growth rate (SGR) of the juvenile orange-spotted groupers decreased significantly with increasing PS-NP exposure concentrations (0.158% ± 0.032%, 0.095% ± 0.020%, and 0.074% ± 0.016% for 0, 300, and 3000 μg/L PS-NP groups, respectively). These results suggest that marine PS-NPs are harmful to the digestive system of juvenile fish and highlight the importance of evaluating the long-term impact of NPs in reshaping marine populations.

The Potential Advantage of Myo‐Inositol as a Dietary Supplement for Juvenile Hybrid Grouper (Brown‐Marbled Grouper Epinephelus fuscoguttatus ♀ × Giant Grouper Epinephelus lanceolatus ♂)

AbstractAn 8‐week feeding trial was conducted to estimate the optimum dietary myo‐inositol (MI) requirement for juvenile hybrid grouper (Brown‐marbled Grouper Epinephelus fuscoguttatus ♀ × Giant Grouper E. lanceolatus ♂). Myo‐inositol was supplemented at 0 (control group), 150, 300, 600, 900, 1,200, and 2,000 mg/kg of diet. Basic diet contained no MI. Each diet was randomly fed to quadruplicate groups of juveniles, and each tank was stocked with 30 fish (initial weight = 7.40 ± 0.01 g [mean ± SD]). Results showed that the addition level of MI exerted no significant effect on the survival rate, feed conversion ratio, or protein efficiency ratio of juvenile grouper (P > 0.05). However, the weight gain rate in the 150‐mg/kg group was significantly higher than that in the control group (P < 0.05). The total cholesterol levels in the serum of the control and 150‐mg/kg groups were significantly higher than those of the other groups, and the triglyceride level in the 150‐mg/kg group was significantly lower than those in the other groups. The glutamine aminotransferase level was significantly higher in the control group than in the supplemented groups, but no significant difference in lysozyme activity was observed. In the liver, superoxide dismutase activity in the control group was significantly lower than that in the 150–900‐mg/kg groups, and the total antioxidant capacity in the 150‐mg/kg group was significantly higher than those in the other groups. Broken‐line regression analysis showed that the MI required for juvenile hybrid grouper was 181.47 mg/kg diet based on weight gain rate, which can significantly improve growth performance and increase the activity of serum and liver enzymes.

Comparison of selenomethionine and hydroxyselenomethionine on tissue selenium retention, and antioxidative capacity of giant grouper, Epinephelus lanceolatus , fed diet with soybean meal

The study aims to evaluate the effects of two organic selenium (Se) sources, selenomethionine (SeMet) and hydroxyselenomethionine (OH-SeMet), on tissue Se retention, and antioxidative capacity of giant grouper, Epinephelus lanceolatus, fed diets with soybean meal (SBM). The control diet containing 32.92% SBM (replaced 40% fish meal protein) was supplemented with 0.3, 0.6 and 1.0 mg Se/kg of SeMet and OH-SeMet. A reference diet with fish meal (FM) as main protein source was also included for comparison. The eight experimental diets were each fed to triplicate groups of grouper juveniles (initial weight: 25.99 ± 0.04 g) in a recirculation system with seawater for 8 weeks. The Se concentrations in whole body, muscle and liver were dependent on dietary Se concentrations, but not on its supplemental forms. Higher hepatic glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT), but lower malondialdehyde (MDA) content, were observed in fish fed the reference diet than in fish fed the control diet. The results indicated that dietary FM protein replaced by SBM at 40% depressed growth performance, Se retention and antioxidative capacity of giant grouper. Both Se sources supplementation enhanced Se retention and antioxidative capacity, but not growth performance of the fish.

Hematological analysis of hatchery-reared and wild juveniles of pink salmon <i>Oncorhynchus gorbuscha</i> and chum salmon <i>Oncorhynchus keta</i> in Sakhalin Region

State of blood cells is examined for juveniles of pink and chum salmon sampled from Lesnoy Pugachevsky, Taranaisky and Okhotsky hatcheries in Sakhalin in May-June of 2018 and 2019 and caught in the Ochepukha, Pugachevka and Taranay Rivers during their catadromous migration to the sea. Both hatchery and wild juveniles of both species were characterized by high adaptive capabilities evidenced with high content of young forms of erythrocytes in the blood (17.0–31.0 %), significant portion of lymphocytes (60.8–92.0 %), and small number of neutrophils. The high adaptive capabilities were confirmed in the experiment, when juveniles of pink salmon were placed in the seawater without preliminary acclimation, but noticeable changes in the state of blood cells were not revealed both for wild and hatchery-reared specimens. Proportion of different blood cells was highly variable for juveniles of both artificial and natural origin but was more similar between the fry hatched at the same hatcheries or in the same rivers. A case of increased number of neutrophils was noted in 2019 for certain groups of juveniles, with total increasing of platelets in the blood that was explained by an external influence on the juveniles.

Sense of Coherence and Ego-Resiliency as Predictors of Maladaptive Coping Among Juveniles With Different Levels of Delinquency.

The purpose of the study is to determine the role of the sense of coherence and ego-resiliency as buffers for maladaptive coping among juveniles with different levels of delinquency. The study included 561 juveniles referred by a family court to youth education or probation centers throughout Poland. We used SEM to search for relations between variables and the critical ratio test for differences between groups. The results demonstrate that in both groups, the relationships between the components of the sense of coherence and the emotional style were negative. In both groups, the sense of comprehensibility was significantly associated with the search for social contacts. The impact of ego-resiliency on social-diversion coping was significantly stronger for the group with high compared with low demoralization. The study demonstrate that juveniles with a high degree of delinquency are more prone to emotion-oriented coping. Both groups of juveniles use two types of avoidance style to a similar extent. The results show that the stronger the sense of coherence, the less often juveniles cope with stress by reducing emotional tension and by escaping into substitute activities. Furthermore, our findings reveal the dark side of ego-resiliency.

Effects of high level of fermented soybean meal substitution for fish meal on the growth, enzyme activity, intestinal structure protein and immune‐related gene expression and intestinal flora in juvenile pearl gentian grouper

The present study preliminarily investigated the effects of high level of fermented soybean meal (FSBM) protein substituted for fish meal (FM) protein on the growth and intestinal homeostasis of pearl gentian grouper. Seven hundred and twenty juvenile groupers were randomly divided into three groups, including the FM control group, 20% FSBM protein substituted for FM protein group (FSBM20) and FSBM40 group (n = 4). Three iso-nitrogenous and iso-lipidic diets were prepared and fed to fish for 10 weeks. Each barrel of cultural water is 1 m3, using natural light and temperature. Results showed that weight gain, specific growth rate, intestine plica length/width and microvilli length in FSBM groups decreased significantly (p < .05), and the lamina propria width in FSBM groups increased significantly (p < .05). The enzyme activities of glutathione reductase, glutathione peroxidase and total superoxide dismutase in distal intestinal tissues and alanine aminotransferase and aspartate transaminase in liver tissues increased significantly with dietary FSBM addition (p < .05). The pro-inflammatory and immune-related gene expressions of IL1β, IL12, IL32 and TNF-α increased significantly in FSBM40 group (p < .05), while the anti-inflammatory and immune-related gene expressions of IL5, IL10, IgM, CD4 and lysozyme decreased significantly in FSBM40 group (p < .05). The aquaporin protein gene expressions of aqu1, aqu4 and aqu12, and the tight junction protein gene expressions of jam, claudin3, claudin12, claudin15 and ZO-3 decreased significantly (p < .05), while the gene expressions of aqu8, aqu9, aqu10 and ZO-1 increased significantly (p < .05), and the ion transport carrier gene expressions of nkcc and clc decreased significantly (p < .05). 16S high-throughput sequencing showed that at the phylum level, the abundance of Proteobacteria decreased significantly in FSBM40 group (p < .05), while that of Bacteroidetes, Firmicutes, Acidobacteria and Actinobacteria increased significantly in FSBM40 group (p < .05). At the genus level, the top 10 species were Photobacterium, Stenotrophlomonas, Vibrio, Phyllobacterium, Chromohalobacter, etc. The abundance of Photobacterium in FSBM40 group decreased significantly (p < .05), while that of other species increased significantly (p < .05). High level of FSBM substituted for FM resulted in a significant decrease in the functional abundance of aerobic_chemoheterotrophy and chemoheterotrophy in FSBM40 group (p < .05), while animal_parasites_or_symbiont abundance increased significantly in FSBM40 group (p < .05). Present study showed that experimental level of FSBM had a significantly negative effect on the growth performance, intestinal mucosa structure and intestinal flora composition in pearl gentian grouper.

Dietary supplementation of fermented lemon peel enhances lysozyme activity and susceptibility to Photobacterium damselae for orange-spotted grouper, Epinephelus coioides

The waste recycling of lemon peel, as a functional feed additive in aquafeed was evaluated by estimating the effects of fermented lemon peel (FLP) supplementation in diet on growth performance, innate immune responses, and susceptibility to Photobacterium damselae of grouper, Epinephelus coioides. A basal diet was added FLP at 0%, 1%, 3%, and 5%. Four tested diets were each fed to juvenile grouper (initial weight: 15.89 ± 0.10 g, triplicate groups) in a recirculation rearing system for eight weeks. Fish fed diets with 0%–3% FLP exhibited higher (p < 0.05) final weight, weight gain, and feed efficiency than fish fed the 5% FLP-diet. After challenge test, fish fed the 3% FLP-diet appeared the lowest mortality, followed by fish fed the 1% FLP-diet, and lowest in fish fed 0% and 5% FLP-diets. Plasma lysozyme activities were higher in fish fed diets with FLP than in fish fed the FLP-free control diet before challenge test. After challenge, fish fed diets with 1% and 3% FLP showed highest lysozyme activities, followed by fish fed the diet with 5% FLP, and lowest in fish fed the control diet. Hepatic malondialdehyde content was higher in fish fed the control diet than in fish fed diets with 1%–3% FLP. Results found that diets supplemented with 1%–3% fermented lemon peel can enhance lysozyme activity and resistance to pathogen P. damselae of grouper.

Optimizing the fatty acid profile of novel terrestrial oil blends in low fishmeal diets of rainbow trout (Oncorhynchus mykiss) yields comparable fish growth, total fillet n-3 LC-PUFA content, and health performance relative to fish oil

Identifying and effectively utilizing suitable, novel, terrestrial oil sources either alone or as blends to replace fish oil (FO) is a prerequisite for improving the sustainability of global aquaculture. Therefore, the present study evaluates several novel terrestrial oil blends (TOBs), optimized for their fatty acid profile, as alternatives to FO in low fishmeal diets fed to rainbow trout (Oncorhynchus mykiss) and describes the subsequent effects on fish growth, fatty acid composition and health. Insect oil (IO), genetically modified canola oil (CO), palm oil (PO) and linseed oil (LO) were used for the formulation of three TOBs viz., TOB-1 (30%IO+36%CO + 34%LO), TOB-2 (40%PO + 20%CO + 40%LO) and TOB-3 (50%TOB-1 + 50%TOB-2). Formulas TOB-1 and TOB-2 considered the total fatty acid profile based upon the general FO fatty acid profile, published fatty acid research for rainbow trout, and the fatty acid requirements of rainbow trout. A low fishmeal based basal diet containing 44% crude protein was formulated, and FO, TOB-1, TOB-2 and TOB-3 were incorporated in the basal diet to prepare the experimental diet groups, Control, TOB-1, TOB-2 and TOB-3, respectively. All experimental diets were fed to triplicate groups of rainbow trout juveniles (initial weight 7.9 ± 0.02 g) for 9 weeks. Growth performance (final weight, percent weight gain and specific growth rate) in TOBs fed groups were equal to the FO-based control group. Fish fed the TOB-3 diet consumed more feed followed by the control and TOB-1 diet groups. Significantly lower feed intake was observed in the TOB-2 diet group. Feed conversion ratio and protein efficiency ratio were not significantly influenced by dietary oil sources. Fish fed the control diet showed significantly higher hepatic lipid content compared to TOB groups, followed by TOB-2, TOB-3, and TOB-1, which was significantly lower in hepatic lipid content. Muscle lipid content and whole-body major nutrient compositions were not significantly influenced by the dietary oil sources. Fatty acid composition of muscle and liver reflected that of the diets. Maximum values for n3 LC-PUFAs (EPA and DHA), lauric acid (C12:0) and C18:3n-3 were observed in the FO, TOB-1 and TOB-2 groups, respectively. Except for C12:0, muscle saturated fatty acid contents were significantly lower in TOBs-based diet compared to the FO-based control diet fish. As expected, muscle C12:0 content was significantly higher in the TOB-1 group followed by the TOB-3 group. TOB-2 and control groups had significantly lower content of C12:0. The fillet total n-3 LC-PUFA was significantly higher in fish fed the control diet group followed by TOB-3 and TOB-2 groups, TOB-1 showed significantly lower content of total n-3 LC- PUFA. Hepatic delta-5 desaturase (Δ5fad), delta-6 desaturase (Δ 6fad) and fatty acid elongase-2 (Elovl-2) gene expressions were significantly influenced by dietary oil sources, where TOB-based groups showed higher Δ6fad and Elovl-2 expressions. Measured innate immunity and antioxidant markers were not affected by TOBs. Finally, we concluded that TOBs could serve as a substitute for FO in rainbow trout feed without negatively impacting performance. Moreover, fillet total n-3 LC-PUFA of TOB-fed fish satisfies the suggested daily serving for humans.

First construction of interspecific backcross grouper and genome-wide identification of their genetic variants associated with early growth

Backcross is a powerful tool in germplasm improvement, which is able to transfer excellent traits from one species to another. Grouper is currently one of the most popular species for aquaculture in Asian. For improving growth rate, in the present study, we firstly constructed interspecific backcross grouper by male hybrid grouper (E. fuscoguttatus♀ × E. lanceolatus♂) with female parent E. fuscoguttatus. In addition, the quality and fertility of gametes, skin pattern, growth rate and genetic relationship were analyzed for the backcross grouper and its parents. Moreover, since many grouper species exhibit significant growth differences at juvenile stage, resulting in severe cannibalism, a genome-wide association analysis was performed on the growth traits of backcross juvenile. As results, 4 significantly and 136 suggestively growth-related SNPs were detected. A set of 51 potential candidate genes were identified within the associated QTLs. These genes are not only involved in energy metabolism and development, but also closely related to stress tolerance, immune response and visual perception. The successful construction of interspecific backcross promotes the development of grouper industry and provides valuable breeding population for analyses of interested trait-related markers. The growth-related SNPs and genes contribute to understanding of influence factors about growth difference in juvenile grouper.

Insect meal inclusion as a novel feed ingredient in soy-based diets improves performance of rainbow trout (Oncorhynchus mykiss)

The additive effects of insect meal supplementation to diets containing a high soy protein inclusion were evaluated for growth performance, antioxidant potential and fillet nutritional quality of juvenile rainbow trout (Oncorhynchus mykiss). A basal diet (Soy) with a high-level soy protein (21% soybean meal, SBM plus 4–5.5% soy protein concentrate, SPC) was compared to similarly formulated soy-based diets supplemented with low (8%) and high levels (16%) of insect meal for diet groups Soy + IM Low and Soy + IM High, respectively. A high-level fishmeal (24%) based positive control diet (Fish meal) was also produced. All diets were iso‑nitrogenous (44%) and isolipidic (20%) and were fed to triplicate groups of rainbow trout juveniles (initial weight 32 ± 0.0 g) over the course of a 10-week trial. Fish fed the positive control diet showed significantly higher final weight, % weight gain (%WG) and specific growth rate (SGR) compared to the Soy + IM High and Soy diet groups, but these parameters were not significantly different from the Soy + IM Low diet group. The Soy and Soy + IM High diet groups showed significantly lower final weight, % WG and SGR. Feed efficiency and protein efficiency ratio was numerically higher in fish fed the Fish meal positive control diet followed by the Soy + IM Low and Soy and Soy + IM High diet groups, respectively. Among somatic indices, condition factor (CF) was significantly influenced by IM supplementation and the Soy + IM High diet group showed significantly lower CF compared to other dietary groups. Addition of insect meal significantly increased whole body amino acids viz., arginine, histidine, valine and threonine content. Insect meal supplementation significantly increased muscle α-linolenic acid content. However, α-linolenic acid content in fish fed the Soy + IM High diet was not significantly different from fish fed the Fishmeal positive control diet. Insect meal supplementation did not significantly influence EPA + DHA, total n-3 PUFA and monounsaturated fatty acid content in the muscle, whereas the significantly highest EPA/DHA and total monounsaturated fatty acids were detected in the fishmeal based positive control diet compared to other dietary treatment. The liver gene expression pattern for Δ5 desaturase was significantly higher in the Soy + IM Low diet fish, while Δ6 desaturase and fatty acid synthase (FAS) were significantly higher in Soy (basal) and Soy + IM Low diet fed fish. Elongase and fatty acid binding protein (FABP) were not significantly influenced by insect meal supplementation. Regarding the antioxidant potential, Soy diet group showed significantly higher superoxide dismutase (SOD) activity compared to insect meal included groups and positive control diet group. Glutathione peroxidase (GPX) activity was significantly reduced in Soy + IM High diet compared to other dietary groups. Finally, we conclude that insect meal inclusion at a low level (8%) is beneficial for increased growth and select fatty acid restoration for rainbow trout fed soy-based feeds.

Population dynamics of sperm whales (Physeter macrocephalus) in Guadeloupe, French Caribbean: A mark‐recapture study from 2001 to 2013

AbstractSperm whales are present along the Caribbean islands in family groups of mature females, juveniles, and newborns. Their abundance and demographic rates remain poorly known. Using photo‐identification data, we estimated the abundance and annual survival of sperm whales in Guadeloupe from January to April 2001–2013. A total of 1,492 photographs of tail flukes were scored (ranging from 1 to 5) in terms of quality (Q) and marking (M) level. A total of 789 photographs were selected with Q ≥ 3 and M ≥ 3, corresponding to 109 individually identified adult females or immatures of both sexes. Capture histories were built and analyzed using the Pollock's robust design capture‐mark‐recapture model. The study consisted of 13 primary periods sequenced in 5–8 secondary periods. Mean annual survival rate of residents was 0.945, 95% CI [0.864, 0.979]. Abundance varied between years from 75 to 35 individuals. The geometric growth rate over the period 2001–2013 was 0.938, 95% CI [0.878, 0.997], suggesting a population decline of −6.2%/year. Sperm whales are moving between Guadeloupe and Dominica, with a high temporary emigration rate (0.163) and 50% of the individuals of Guadeloupe resighted in Dominica. These results highlight the fragility of the population and the necessity to consider it as one unit.

Dietary carbohydrate‐to‐lipid ratios modulate juvenile hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ E. lanceolatus ): Effects on growth, serum biochemistry, intestinal digestion and hepatic metabolism of glucose and lipid

A 56 day feeding trial was conducted to study effects of different carbohydrate-to-lipid (CHO.L−1) ratios on growth, serum biochemistry, intestinal digestion and hepatic metabolism of glucose and lipid in juvenile hybrid grouper (Epinephelus fuscoguttatus × ♂ E. lanceolatus). Results showed that moderate CHO.L−1 ratio resulted in better growth performance (p < .05). In serum, glucose, insulin and alanine aminotransferase were enhanced as CHO.L−1 ratios increased, whereas cholesterol was reduced (p < .05). Increased CHO.L−1 ratios resulted in raised activity of amylase and reduced activity of lipase in gut (p < .05). Gene expression related to glucose transporters improved (p < .05). Enzyme activity and gene expression involved in hepatic glycolysis improved in a limited manner, whereas enzyme activity and gene expression related to hepatic gluconeogenesis and lipolysis were inhibited in high CHO.L−1 ratio group. Enzyme activity of hepatic lipogenesis showed an elevated trend, including acetyl-CoA carboxylase and fatty acid synthase (p < .05). In conclusion, different dietary CHO.L−1 ratios affected growth, serum biochemistry, intestinal digestion and hepatic metabolism of glucose and lipid in grouper. Moreover, juvenile grouper could utilize diet containing moderate CHO.L−1 ratio.

Mechanisms by Which Fermented Soybean Meal and Soybean Meal Induced Enteritis in Marine Fish Juvenile Pearl Gentian Grouper.

Soy meals can cause intestinal inflammation and even injury in animals, especially infants and juvenile individuals. This study investigated the effects of fermented soybean meal (FSBM) on the growth and intestinal homeostasis of juvenile pearl gentian grouper and examined the mechanisms by which FSBM and soybean meal (SBM) induced enteritis in fish, using “3+2” full-length transcriptome sequencing. We randomly assigned 720 female juvenile groupers into three treatment groups: FM control group, 20% FSBM group (FSBM20), and FSBM40 group (n = 4). Three iso-nitrogenous (50% protein) and iso-lipidic (10% lipid) diets were prepared and fed to fish for 10 weeks. The water volume in each barrel was about 1 m3, using natural light and temperature. Results showed that dietary FSBM, at experimental level, significantly affected fish growth and intestinal structure negatively and significantly increased enteritis indices. The degree of intestinal injury and inflammation was determined by the enzyme activities of trypsin and lysozyme, and the contents of IgM, C3, C4, and malondialdehyde, and the expressions of pro-inflammatory genes (IL1β, IL8, IL17, and TNFα) and anti-inflammatory genes (IL4, IL10, and TGFβ1). Full-length transcriptome analysis identified 2,305 and 3,462 differentially expressed genes (DEGs) in SBM40 and FSBM40 groups, respectively. However, only 18.98% (920/5,445) of DEGs had similar expression patterns, indicating that high levels of SBM40 and FSBM40 have different metabolic strategies. KEGG enrichment analysis indicated that among the significant pathways, ~45% were related to immune diseases/systems, infectious diseases, and signal transduction in both SBM and FSBM groups. Based on PacBio SMRT sequencing, nine toll-like receptor (TLR) members, including TLR1, TLR2, TLR3, TLR5, TLR8, TLR9, TLR13, TLR21, and TLR22, were detected in intestinal tissues of pearl gentian grouper. TLR-MyD88-NF-κB signaling pathway played an important role in the development of FSBM- and SBM-induced enteritis in pearl gentian grouper; however, TLR receptors used in SBM and FSBM groups were different. TLR1, TLR8, TLR13, and TLR22 were the main receptors used in FSBM group, while TLR5, TLR8, TLR9, TLR21, and TLR22 were the main receptors used in SBM group. Present study provides valuable theoretical references for further research on soy protein-induced enteritis in fish.

An immersion subunit vaccine loaded by single-walled carbon nanotube protects pearl gentian grouper from viral nervous necrosis virus

Grouper is an important cultured fish in China. However, a large number of larval and juvenile groupers dead from the infection of nervous necrosis virus every year, which calls for an effective prevention and control measure. In this study, recombinant major capsid protein (MCP) of nervous necrosis virus (NNV) was produced through a prokaryotic expression vector as a subunit vaccine. We processed single walled carbon nanotube (SWCNTs) by conc H2SO4 and conc. HNO3 to make it a carrier for the vaccine. The fish were inoculated by immersion immunization for 6 h and three concentrations included 5, 10, 20 mg/L were set. Antibody levels, immunization related enzyme activities of acid phosphatase, superoxide dismutase, and alkaline phosphatase in serum as well as the transcription of immune genes (IgM, Mx1, IL1-β, TNFα, CD4, CD8. MHC I, and MHC II) were tested. According to the results, the data of vaccine with the carrier had a significant increase compared with that without. After the virus challenge test, the vaccines carried by SWCNTs with concentrate of 5, 10, 20 mg/L of provided the relative survival rates of 28.57%, 50.62%, 70.76% respectively, while 16.67%, 25.93%, 33.33% were provided by the vaccines without SWCNTs. Besides, the body length and weight of a fish were measured every week, the data showed that there was no significant difference among the groups. The research showed the immersion subunit vaccine loaded by SWCNTs can protect pearl gentian grouper from NNV.

Optimum protein requirement of juvenile orange-spotted grouper (Epinephelus coioides)

The purpose of subject was to explore the optimum protein requirement of juvenile grouper (Epinephelus coioides). In the test, 450 juveniles with an average weight (10.02 ± 0.22) g were randomly divided into six groups with triplicate, and were fed with 350, 400, 450, 500, 550 and 600 g/kg iso-lipid test diet twice 1 day for 8 weeks, respectively. The results showed that: (1) With the increase of protein level, the body weight gain rate and specific growth rate first increased and then reduced, while the feed coefficient rate first decreased and then increased, while the protein efficiency significantly decreased (P < 0.05). (2) With the increase of protein level, the condition factor, hepaticsomatic index and visceralsomatic index significantly reduced (P < 0.05). (3) With the increase of protein level, the crude protein content of whole fish and muscle gradually increased, while the crude lipid content gradually decreased. (4) High-protein diet (550–600 g/kg) significantly increased the plasma total protein content and decreased the triglyceride content of orange-spotted grouper (P < 0.05). (5) Compared with the 350 g/kg group, 500, 550, 600 g/kg groups significantly increased the activities of glutamic-pyruvic transaminase and glutamic oxaloacetic transaminase in liver (P < 0.05). (6) With the increase of protein level, the protease activity of intestine first increased and then decreased, and reached the maximum at the protein level of 500 g/kg, while lipase and amylase decreased significantly (P < 0.05). (7) The activities of acid phosphatase, superoxide dismutase and lysozyme in liver increased first and then decreased with the increase of protein level, and reached the maximum in the 400 g/kg protein group. According to the analysis specific growth rate, the optimum protein level of juvenile orange-spotted grouper is 521.84 g/kg.

Optimal dietary lipid requirement for juvenile Asian red-tailed catfish (Hemibagrus wyckioides): Dietary lipid level for Hemibagrus wyckioides

This study investigated the effects of dietary lipid content on growth rate, feed utilization, digestive enzyme activity, and antioxidant capacity of juvenile Asian red-tailed catfish (Hemibagrus wyckioides), and thereby to evaluate the optimal dietary lipid requirement. Five isoproteic diets were prepared to contain varied levels of dietary lipid (3 %, 5.5 %, 8 %, 10.5 %, and 13 %). Each diet was fed to triplicate groups of juveniles (average body weight 3.20 g) in a recirculating farming system maintained at 28 ± 1 °C. Daily gain coefficient (DGC) and protein efficiency ratio improved steadily with the dietary lipid content up to 10.5 %, and then reached a plateau. Similarly, protein retention increased gradually with the dietary lipid content up to 13 %. Conversely, lipid retention decreased linearly with increasing dietary lipid content, but no significant difference was found among juveniles fed diets with 8 %, 10.5 %, and 13 % lipid. The optimum feed conversion ratio (FCR) was observed in juveniles fed diets with 10.5 % or 13 % lipid. Plasma insulin-like growth factor 1 level increased steadily with the dietary lipid content up to 8 %. However, plasma amino methyl propanediol, aspartate aminotransferase and alanine aminotransferase activities depressed generally with increasing dietary lipid content. Besides, the highest hepatic peroxidase, catalase, glutathione peroxidase, and alkaline phosphatase activities were found in juveniles fed diet with 10.5 % lipid. Single-slope broken-line regression analysis of DGC or FCR response to varied levels of dietary lipid showed that the optimal dietary lipid requirement of juvenile H. wyckioides was 11.1 % or 9.4 % of diet containing 42 % protein, respectively.

The applications of plasmonics biosensor and bamboo char filtration to the prevention of nervous necrosis virus infection in grouper farming ponds

Fiber optic particle plasmon resonance (FOPPR) biosensors have been useful tools to determine a variety of biological samples including viruses with superior detection limits than using conventional ELISA methods. In addition, without using tedious procedures required in ELISA protocols, FOPPR method can minimize contamination interferences and obtain accurate results in timely fashion. FOPPR biosensor is potentially a suitable virus detection device to implement in fish farms. In Taiwan, aquaculture products such as groupers suffer tremendous loss because of ineffective disease prevention efforts. The infected signs are not detected in the early stage before severe outbreak to cause uncontrollable consequences. Therefore when the virus level is low, using highly sensitive FOPPR biosensors to monitor pond water is a promising means to improve the effectiveness of aquatic product disease prevention by taking water treatment actions. We have also developed FOPPR assays to determine nervous necrosis virus (NNV), which cause massively high mortality rate (∼90%) in larva and juvenile stages of grouper species. Using coat proteins of NNV as standards in 2% salt water, the detection limit of 100 ng/mL is obtained. This limit is nearly 2 orders of magnitude lower than that using ELISA assays and adequate to indicate the severance level of NNV outbreak. Ground meat of infected juvenile grouper was diluted with saline to prepare simulated water samples. Ultra-low virus level of 40k TCID50 per mL is found in filtrate. The comparison determination data between using FOPPR and quantitative PCR methods are acceptable too. Unlike RT-PCR method not able to detect NNV RNA in pond water until severe infection, we demonstrate that FOPPR assay can detect NNV in pond water at very low NNV level at early infection stage, a couple of days prior to the outbreak occurrence. We also show that commercial FOPPR biosensor maintains stable immuno-sensing signal readout in indoor aquaculture settings. We will also discuss the potential applications of using FOPPR to monitor grouper larvae pond water to activate biochar filtration equipment when infection sign occurs.

Physiological response of rainbow trout (Oncorhynchus mykiss) to graded levels of Hermetia illucens or poultry by-product meals as single or combined substitute ingredients to dietary plant proteins

In the last decades, processed animal proteins, such as poultry by-product meal (PBM) and insect meals have received great attention as sustainable and nutritious aquafeed ingredients. The aim of the present study was to evaluate growth performances, liver and gut histology, macromolecular composition and inflammatory response in rainbow trout (Oncorhynchus mykiss) fed diets deprived of fish meal, where graded levels of vegetable protein-rich ingredients, were replaced by defatted Hermetia illucens pupae meal (HM) or PBM, singly or in combination. To this end eight grossly iso‐proteic (45% DM), isolipidic (26% DM) and isoenergetic (23.5 MJ/kg DM) were offered each to triplicated groups of juveniles' fish in a 91 days feeding trial. A diet rich in vegetable protein derivatives high in soybean meal (CV) was prepared to have a 10:90 and 20:80 fish to vegetable protein and lipid ratios respectively. By contrast, a fish-based diet (CF) was formulated with opposite fish to vegetable protein and lipid ratios. Six more diets, were obtained by replacing graded levels of protein (10, 30 and 60%) of diet CV, by protein from a defatted Hermetia illucens pupae meal and/or poultry by-product meal, singly or combined, while maintaining the same vegetable to fish lipid ratio as in the CV diet.Relative to diets CV and CF, a medium to high substitution (30 and 60%) of dietary vegetable protein-rich ingredients, with HM and/or PBM resulted in improved growth performance as well as in a minor incidence of distal intestine morphological alterations. The diet including both the test animal proteins led to nearly the best overall response in terms of growth and gut/liver health. Both HM and PBM when included at moderate or high levels in the diet, resulted in a downregulation of the expression of inflammatory-related genes relative to diet CV. This effect was greater with HM than that observed with PBM and goes beyond the parallel reduction of vegetable protein and SBM levels in the same diets, suggesting a beneficial role of insect meal that warrant further investigation.The results obtained so far, provide support to a reliable use of alternative/underexploited protein and lipid sources [(HM) or (PBM)] in developing a new generation of sustainable and healthy trout diets that meet the circular economy principles.

Effects of fish meal under different storage conditions on growth, serum biochemical indices and antioxidant capacity for juvenile grouper Epinephelus coioides

This research aimed to assess effects of fish meal under different storage conditions on growth and antioxidant capacity for juvenile grouper within eight weeks. The healthy fish samples (initial body weight = 18.75 ± 0.05 g) were irregularly distributed to 0.5 m3 barrels with 28 fish per barrel, fed with each diet in the three replicate groups. Fish meals (FMs) were stored at 4°C (experiment 1) and room temperature (30 ± 2°C, experiment 2) for 45, 90 and 135 days, and the data of VBN, HA, AV and TBA were detected. Seven iso-nitrogenous and iso-lipidic diets were prepared and denoted as fresh fish meal FFM (control group), 4-FM45, 4-FM90, 4-FM135, RT-FM45, RT-FM90 and RT-FM135, respectively. Prolonged storage time, the volatile base nitrogen, acid value, histamine and thiobarbituric acid contents of FM increased significantly (p < .05). The growth condition and feed utilization of experimental fish were not significantly affected (p > .05). Prolonged storage time, in experiment 1, the catalase (CAT), the superoxide dismutase (SOD) activities and the malondialdehyde (MDA) contents initially increased dramatically and then decreased (p < .05). The reactivity of CAT mRNA in FFM group was significantly higher than that in other treatment groups (p < .05). In experiment 2, CAT activity decreased significantly (p < .05), whereas the MDA contents increased sharply (p < .05). SOD activity and CAT expression in the liver initially increased and then decreased (p < .05). The mRNA level and enzyme activity of trypsin decreased (p < .05) in experiment 1 and 2. In summary, storage of FM (within 135 days) cannot improve the growth and feed utilization of juvenile grouper but weaken the antioxidant capacity of the liver.

Health status in gilthead seabream (Sparus aurata) juveniles fed diets devoid of fishmeal and supplemented with Phaeodactylum tricornutum

To enhance fish general health, feeds can be supplemented with health-promoting additives, reducing the need to use chemotherapeutics. Incorporation of marine algae biomasses in aquafeeds has been shown to improve fish immune status by enhancing innate immune response. This study evaluated the effects of Phaeodactylum tricornutum incorporation in feed by two different processes, either as freeze-dried biomass or broken cell wall biomass, on fish health status and performance. Triplicate groups of gilthead seabream juveniles (13.3 ± 0.3 g) were either fed a control diet (CTRL) with an extreme (i.e., 0% fishmeal), nutritionally balanced, formulation, or two experimental diets formulated as the CTRL with 1% inclusion of the microalga P. tricornutum at the expense of wheat meal: BC diet contains P. tricornutum broken cells and WC diet microalgae whole cells. After 2 and 12 weeks of feeding, blood was collected for hematological procedures, whereas plasma and mucus were sampled for immune parameters. Head-kidney, liver, and white skeletal muscle were also collected for gene expression measurements. No major differences were observed in hematological nor plasma humoral parameters after 12 weeks irrespective of dietary treatment. Arrays of 29–31 genes were analyzed in the different tissues, revealing an early dietary effect (2 weeks) in a tissue-specific pattern. In the liver, the major effect was found in the GH/IGF axis and in muscle there was a late downregulation of myostatin (mstn) gene, mainly due to WC diet, even though all fish had similar growth performance. Regarding the head-kidney, BC diet led to alpha-2-macroglobulin (a2m) gene upregulation. Also, the same treatment showed increased mucus alternative complement pathway and bactericidal activity at 2 and 12 weeks, respectively. Hence, it seems that BC diet has a potential stimulatory effect that might be relevant as a prophylactic measure before a predictable stressful event.