Lateolabrax Japonicus Research Articles

Natural micropatterned fish scales combing direct osteogenesis and osteoimmunomodulatory functions for enhancing bone regeneration

Surface topography of implants to remodel osteoimmune microenvironment and osteogenic differentiation by modulating macrophage polarization has been regarded as a valuable strategy for advanced bone materials developments. Fish scales, considered as fish waste, show rich anisotropic ridged micropatterns on the surface and similar components to natural bone. Here, we present a topography strategy enhancing bone regeneration using the Lateolabrax japonicus scales surface microtopography as physical cues to program cell behaviors. The anisotropic ridged micropatterned surfaces and mineralized collagen synergistically programmed cells directional arrangement and induced the M2-phenotype polarization of macrophage to modulate the osteoimmune microenvironment by promoting anti-inflammatory cytokines secretions. Furthermore, anisotropic surface topography and mineralized collagen synergistically precipitated osteogenic differentiation of marrow mesenchymal stem cells via Wnt/β-catenin pathway. In vivo, the implanted fish scales significantly increased M2/M1 macrophage ratio, up-regulated anti-inflammatory and pro-healing cytokines expressions, promoted osteogenesis and bone formation. In conclusion, Lateolabrax japonicus scales enriched with anisotropic ridged micropatterns and mineralized collagen components synergistically expedite osteogenic differentiation and bone regeneration via programming cell orientation and modulating osteoimmune microenvironment, which provided a novel candidate implant for bone repair and boosted sustainable utilization of bio-resources.

Immune Activation Following Vaccination of Streptococcus iniae Bacterin in Asian Seabass (Lates calcarifer, Bloch 1790).

Juvenile Asian seabass (Lates calcarifer) (body weight 10 ± 0.7 g) were intraperitoneally injected with 1012 CFU fish-1 of formalin-killed Streptococcus iniae. The protective efficacy of the vaccine on survival and infection rate was assessed upon challenge at 4, 8, 12, 20, and 28 weeks post-vaccination. The results revealed that the challenged vaccinated fish showed no mortality at all time points, and the control fish presented 10-43.33% mortality. The infection rate at 2 weeks post-challenge was 0-13.33% in the vaccinated fish and 30-82.35% in the control group. At 8 weeks post-vaccination, the vaccinated fish showed comparable ELISA antibody levels with the control; however, the antibody levels of the vaccinated fish increased significantly after the challenge (p < 0.05), suggesting the presence of an adaptive response. Innate immune genes, including MHC I, MHC II, IL-1β, IL-4/13B, and IL-10, were significantly upregulated at 12 h post-challenge in the vaccinated fish but not in the control. In summary, vaccination with S. iniae bacterin provided substantial protection by stimulating the innate and specific immune responses of Asian seabass against S. iniae infection.

Effects of Tricaine Methanesulphonate (MS-222) on Physiological Stress and Fresh Quality of Sea Bass (Lateolabrax maculatus) under Simulated High-Density and Long-Distance Transport Stress.

This study aimed to evaluate the effect of different transport densities on water deterioration, physiological response, nutrients, and fresh quality of sea bass (Lateolabrax maculatus) at 30 mg/L tricaine methanesulphonate (MS-222) before and after simulated live transport. The results indicated that the addition of MS-222 could effectively decrease mortality compared with the control (CK) sample during the simulated live transport. The concentration of dissolved oxygen was lower and the total ammonia nitrogen was higher in the high transport density samples than those of low transport density samples after 72 h in transport. The level of blood cortisol (COR), glucose (GLU), lactic acid (LD), aspartate aminotransferase (AST), alanine aminotransferase (ALT) for the sea bass were significantly higher compared with the CK sample (p < 0.05) during the simulated live transport and after 12 h of recovery. These results indicated that the sea bass presented a strong stress response in high-density transport. The glycogen, fat, and protein of the sea bass were degraded to supply the energy for the body in the process of surviving the transportation, resulting in the decreased nutrient content in the muscle, which recovered to the initial level (CK) after 12 h. The increase in flavor substance content, such as free amino acids, nucleotides, organic acids, and minerals, enhanced the special flavor of the muscle during the simulated live transport. This study demonstrates that the addition of MS-222 at 30 mg/L to the transport water is an effective method for live fish to realize low mortality and physiological response during high-density and long-distance transport.

Effects of starvation on the pharmacokinetics and optimal dosages of florfenicol and associated serum biochemistry in Asian seabass (Lates calcarifer).

Starvation has influence on physiology and pharmacokinetic (PK) characteristics of many drugs in land animals. However, similar PK information in fish is lacking. The current study examined the effects of starvation on fish PK, taking florfenicol (FF) in Asian seabass as an example. FF was orally administered at a single dose of 10mg/kg into 35-day starved fish reared at 25 and 30°C and the serum FF concentration was analyzed by HPLC-FLD. At 30°C, the absorption and elimination half-lives of the starved fish were increased by 30% (from 0.44 to 0.57 h) and 55% (from 7.2 to 11.18 h), respectively. The volume of distribution, clearance, and area under the curve were changed from 1.25 to 0.71 L/kg, 0.120 to 0.044 L/kg/h, and 88 to 228 h·μg/ml,respectively. Similar starvation-induced PK changes were also observed at 25°C. The serum biochemical parameters, mainly the alanine aminotransferase, aspartate aminotransferase, and glucose levels, were significantly reduced in the starvation group. Overall, FF absorption, distribution, and elimination rates were reduced by starvation, resulting in four to five times lower optimal dosage than the non-starved fish. Drug treatment in starved fish should be treated with caution as overdosing and/or tissue residues could perceivably occur.

Effects of essential oil of Magnolia denudata on spotted seabass (Lateolabrax maculatus) during simulated live transportation

The essential oil of Magnolia denudate (MDO) is an effective anesthetic and sedative on spotted seabass (Lateolabrax maculatus). To improve animal welfare and transportation effectiveness, this study evaluated the effects of MDO on water quality, blood biochemical, and tissue damage after the transportation of L. maculatus (164.16 ± 15.40 g). A base group (no MDO and no transport) and 0 (control group), 10, and 20 mg/L MDO during simulated transportation treatments of 5 h were involved. Every treatment has four replicates with four fish transported in a plastic box (34 × 22.5 × 19 cm) with 5 L water at a fish density of 130 g/L and a shake rate of 60 rpm. At the end of the transportation simulation, no mortality was observed. Fish were immediately sampled for blood collection, liver and brain removal. Compared to the control group, the MDO groups showed significantly lower ammonia in water, lower cortisol level and lactic dehydrogenase activity, higher glucose, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase activities in fish serum (p < 0.05). Superoxide dismutase (SOD), catalase (CAT) activity, glutathione (GSH) concentration decline, and malondialdehyde (MDA) were alleviated in the fish brain when MDO was added to the water. However, SOD and GSH further decreased, but MDA increased in the fish liver in the MDO groups (p < 0.05). These results revealed that the administration of MDO on L. maculatus transportation could alleviate stress and decrease energy metabolism. Due to the 20 mg/L MDO may trigger more serve liver function decline, we suggest 10 mg/L MDO addition in L. maculatus transportation.

Nutritional profiling reveals the effects of dietary zeolite on Asian seabass Lates calcarifer

As costs for nutrition in aquaculture farming escalate, using affordable feeds that provide an optimal combination of nutrients for the fish species of choice is paramount. Natural zeolites have been applied in aquaculture as early as 1977 including feeds in animal nutrition, and moisture and ammonia control of animal manure. In this study, five experimental diets: control, Z1, Z2, Z4 and Z8 containing 0, 1, 2, 4 and 8% of dietary zeolite respectively were investigated for growth performance and immune responses in Lates calcarifer. In general, dietary zeolite supplementation boosted overall growth performance, particularly with Z4 of 4% zeolite supplementation showing the highest Body Weight Gain (BWG) over the other diets. Feed Conversion Ratios (FCR) and Protein Efficiency Ratio (PER) of fish were found to be significantly improved (P &lt; 0.05) by the supplementation of zeolite. Furthermore, no significant changes in the immune and stress responses of fish at both 4% and 8% zeolite supplementation were exhibited, indicating that the presence of zeolites did not impair the immune state of L. calcarifer. This study suggests the suitability of dietary zeolite supplementation and recommends 4% zeolite supplementation to be the most ideal for improved growth performance for L. calcarifer.

A Case of Mycobacteriosis in Cultured Japanese Seabass (Lateolabrax japonicus) in Southern China

Japanese seabass (Lateolabrax japonicus) is an important species of cultured marine fish with high economic value in China. Nevertheless, from May to November 2019, mass mortality among cultured Japanese seabass occurred in Zhuhai City, Guangdong Province of China. Approximately 0.2–0.5% mortality was recorded daily, and the cumulative mortality was up to 30% during this disease outbreak. In this study, the clinical signs and pathological characteristics of diseased fish were investigated. Furthermore, the pathogenicity and antibiotic sensitivity of identified pathogenic bacteria from diseased fish were analyzed. The infected fish showed clinical signs of uncoordinated swimming; anorexia; pigment changes; and a number of 1–5 mm grayish-white nodules in the liver, spleen, and kidney tissues was also found. A bacterial strain, which was designated as ZHLJ2019, was isolated from the diseased fish. To ensure that ZHLJ2019 isolate was the causative agent, a Koch postulate trial was performed. Healthy Japanese seabass were infected by the intraperitoneal injection of 5 × 104, 5 × 105 and 5 × 106 CFU/fish, and cumulative mortalities within 42 days were 75%, 90%, and 100%, respectively. The bacteria colony had traditional morphological and biochemical characteristics similar to that of Mycobacterium marinum. Phylogenetic molecular analyses of 16S rRNA, rpoB, hsp65, erp, and ITS genes confirmed that the isolated strain ZHLJ2019 was M. marinum. The granulomatous inflammation in internal organs of Japanese seabass naturally and experimentally infected with ZHLJ2019 isolate was consistent with the classic pathological features of mycobacteriosis. Drug susceptibility of ZHLJ2019 isolate to 11 antibiotics was determined by broth dilution method in vitro. The minimum inhibitory concentrations (MICs) of minocycline, rifampicin, ethambutol, isoniazid, streptomycin, doxycycline hydrochloride, kanamycin sulfate, levofloxacin, roxithromycin, and prothionamide against the strain ZHLJ2019 were 4, 2, 8, 4, 16, 8, 8, 8, 4, and 8 μg/mL, respectively. The results of this study suggest that M. marinum is the causal agent responsible for the morbidity and mortality of Japanese seabass cultured in intensive brackish water dirt ponds in southern China.

Microplastic and oil pollutant agglomerates synergistically intensify toxicity in the marine fish, Asian seabass, Lates calcalifer

Asian seabass, Lates calcarifer frys were exposed to polystyrene (MP: 0.5 mg/l), oil (0.83 ml/l) and agglomerates (MP + oil + Corexit) as eight treatments in three replicates, and fresh synthetic marine water (control) for 15 days. The synergistic effect was confirmed (P ˂ 0.05) by bio-indicators including RBC count, total plasma protein, aspartate aminotransferase (AST), catalase (CAT), glutathione S-transferase (GST), basophils, thrombocyte and eosinophils percentages. Most of the significant and synergistic effects were observed in the highest doses (5 mg/l MP and 5 mg/l MP-oil-dispersant). Exposure to MP and a combination of MP+ oil caused tissue lesions in gill, liver and intestine. Our results suggest there are no critical health issues for Asian seabass in natural environments. However, the bioaccumulation of MPs, oil, and their agglomerates in consumers' bodies may remain a concern.

The application of Melissa officinalis L. essential oil nanoemulsions protects sea bass (Lateolabrax japonicus) against myofibrillar protein and lipid oxidation during refrigeration

Abstract Objectives The nutrient rich sea bass is prone to oxidation of lipid and protein during refrigeration. Materials and Methods The research was to investigate the effect of different concentrations of Melissa officinalis L. essential oil (MOEO) nanoemulsions on myofibrillar protein (MP) and lipid oxidation in sea bass (Lateolabrax japonicus) during refrigeration at 4 °C. Results The results of thiobarbituric acid reactive substances and mitochondrial membrane potential showed that carboxymethyl chitosan/locust bean gum active coating solutions incorporating 2% MOEO nanoemulsions (C/L-2M) was the most effective in inhibiting lipid oxidation that occurred in sea bass under attack by reactive oxygen species. Low-field nuclear magnetic resonance results showed that C/L-2M maximally slowed the conversion of bound water to free water during storage. The oxidation of lipids and MP disrupted the secondary and tertiary conformations of MP and accelerated protein aggregation and degradation. Conclusions C/L-2M slowed the oxidation of lipids and proteins by inhibiting the oxidation of reactive oxygen species. C/L-2M is a very promising preservative emulsion for the preservation of sea bass.

A strategy to link the changes in the quality traits of Japanese sea bass (Lateolabrax japonicus) muscle and proteins in its exudate during cold storage using mass spectrometry.

In this study, Japanese sea bass (Lateolabrax japonicus) was used as a model to link the changes in the quality traits of fish muscle during storage to the change of protein in muscle exudate. Matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS) combined with variables importance in projection (VIP) analysis, and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), were applied to identify the proteins by analyzing the enzymatic hydrolysates of exudates of fish muscle. The link in the identified proteins to the change in the quality traits of fish muscle during storage was explored using pyramid diagrams. Nine proteins were identified from the exudate of Japanese sea bass muscle during 12 days of storage at 4 °C. Of these, four proteins, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), heat shock protein 90 (HSP90), and peroxiredoxin 1 (PRX1), and beta-actin were found to be responsible for the changes in the quality traits of fish muscle. It is promising to correlate the changes in the quality traits of fish muscle and proteins in muscle exudate via MS-based protein identification and the construction of a relationship diagram to understand the mechanism of muscle change at the molecular level.

Effect of dietary honey supplementation on weight growth performance of Asian seabass (Lates calcarifer)

This study aimed to identify the effect of local bee (Apis dorsata) honey as a feed additive on the growth performance of Asian seabass (Lates calcarifer). The honey was supplemented at 1%, 2%, and 3% per kg diet. The test fish were reared for 35 days in a net placed in a floating-net cage (KJA). The results showed that the dietary honey supplementation affected the absolute weight and specific growth rate (p<0.05). The supplementation of 3% honey per kg diet obtained the highest growth performance compared to other treatments with the weight growth at 42.43 ± 12.78 g, specific growth rate at 1.21 ± 0.37 g/day and survival rate at 100%. The water quality parameters in the rearing tank of test fish were eligible based on the Indonesian National Standard (SNI) of 01-6493.1-2000 about water quality for Asian seabass grow-out rearing.

Probiotics and constant temperature's impacts on asian seabass Lates calcarifer fry growth, survival, and health

This study is conducted to provide information on the effect of temperature and incorporation of probiotics on the growth, survival, and health of Asian seabass L. calcarifer fry. A constant temperature of 30 ± 0.5 °C was applied for larval rearing of Asian bass combined with probiotic supplements (Alteromonas sp. BY-9 and Bacillus cereus BC). Containers for larval rearing were using a polycarbonate tank with a volume of 200 L. The treatments applied were (A) application of temperature and probiotics and (B) without application of temperature and probiotics (Control). Each treatment was repeated six times, and the rearing tanks were positioned in a large tank to form a water bath system. The results of growth of fry during rearing with constant temperature and supplemented of probiotics (A) and control (B) showed different growth profiles. The time needed to reach a body length of 2.5 cm in (A) treatment was only 37 days after hatching, while in (B) treatment, it took two days longer, which was 39 days. In (A) treatment, immunity increased in all target genes by relatively high multiples expression (5 times in CAT, 3-30 times in HSP-70, and 1 -1.6 times in SOD)

Microbiological, chemical and physical attributes and mathematical models for total volatile basic nitrogen formation of Asian seabass (Lates calcarifer) fillets stored under refrigerated and temperature-abuse conditions

Microbiological, chemical and physical attributes and mathematical models for total volatile basic nitrogen formation of Asian seabass (Lates calcarifer) fillets stored under refrigerated and temperature-abuse conditions

Comparative evaluation of different diets on the growth performance and body composition of asian seabass (Lates calcarifer) in HDPE marine cages

Comparative evaluation of different diets on the growth performance and body composition of asian seabass (Lates calcarifer) in HDPE marine cages

Influence of an exogenous androgen, testosterone propionate on milt quality and short-term preservation of milt of Asian seabass Lates Calcarifer

Asian Seabass Lates calcarifer is widely used for pond and cage culture practice in the Kingdom of Saudi Arabia. A studywas carried out to understand the influence of an exogenous androgen, Testosterone propionate (TP) on milt quality ofL. calcarifer. Intramuscular injection of TP at dose 1.0 ml kg-1 was given to mature male fishes grown in a brood stockpond. A control was also maintained without giving hormone injection. After 36 h of injection, milt was collected and miltquality was assessed for colour, sperm cell concentration, motility and viability of spermatozoa. Short-term preservation ofmilt was carried out in oxygen and marine teleost Ringer’s medium at 4oC for 120 h. No significant change was observedin colour and pH of milt, but nature of milt changed from thick to watery due to hormone injection. Enhanced milt volume(14%) and sperm cell concentration (4%) was noticed in fishes from the treatment group 36 h post-injection, when comparedto control. Sperm motility duration and percentage motility were high in treatment fishes than control. Milt preserved inoxygen medium showed high sperm motility and viability when compared to Ringer’s medium. Intramuscular injection ofTP at 1.0 ml kg-1 improved milt volume and quality and therefore can be used for induced breeding of Asian Seabass. Keywords: Asian Seabass, Hormone, Intramuscular injection, Milt quality, Ringer’s medium, Sperm motility, Testosteronepropionate

Detection of pathogenic Vibrio species and antibiogram activity in Asian Seabass (Lates calcarifer) in Tumpat, Kelantan.

Some of Vibrio species is well known as pathogenic bacteria in aquaculture and the marine industry. Its infection is able to generate a massive outbreak and affect the fish population, especially for net caged fish such as seabass. This study was conducted to investigate the prevalence of Vibrio spp. isolated from seabass (Lates calcarifer) in Sri Tujuh Lagoon, Tumpat, Kelantan. Then, to determine the antibiotic resistance in Vibrio isolates. Polymerase chain reaction (PCR) was used to detect Vibrio species using specific primer VR169 and VR744 with estimation base pair size band, 597 bp and further identified by sequencing. On the other hand, antibiotic susceptibility tests were continued by using 13 types of antibiotics; kanamycin (K30), chloramphenicol (C30), neomycin (N10), ampicillin (AMP10), nitrofurantoin (F300), tetracycline (TE30), streptomycin (S10), norfloxacin (NOR10), ciprofloxacin (CIP5), nalidixic acid (NA30), gentamicin (CN10), doxycycline (DO30) and sulfamethoxazole (SXT100). As a result, 14 Vibrio isolates were identified, including Vibrio fluvialis (n=6), Vibrio parahaemolyticus (n=3), Vibrio harveyi (n=2) and each isolate for Vibrio vulnificus, Vibrio alginolyticus and Vibrio spp. The results showed that all isolates were sensitive to most antibiotics except ampicillin, neomycin and streptomycin. The MAR index value was ranging from 0 to 0.31. This study demonstrates the prevalence of Vibrio spp. in seabass and the report on multidrug resistance strains that could be of concern to the fish farmers. In addition, data from this study can be further used in fish disease management plans.

Involvement of MMP-9 in collagen degradation of sea bass (Lateolabrax japonicus): Cloning, expression, and characterization.

Disintegration of intramuscular connective tissue is responsible for postmortem tenderization of fish muscles during chilled storage. Matrix metalloproteinase-9 (MMP-9) was reported to be involved in this process, whereas the mechanism has not been revealed. In the present study, purified type I and V collagens from the connective tissues of sea bass (Lateolabrax japonicus) muscles were first prepared. These two kinds of collagens comprise three polypeptide chains (α), forming a typical triple-helical domain as determined by circular dichroism. The complete coding region of MMP-9 containing an open reading frame of 2070bp encoding 689 amino acid residues was then cloned. The recombinant MMP-9 catalytic domain (rcMMP-9) was expressed in Escherichia coli and exhibited high hydrolyzing activity toward gelatin. Besides, rcMMP-9 was effective in degrading type V collagen rather than type I collagen at 4°C. The enzymatic activity of rcMMP-9 was highly pH-dependent, and its enzymatic activity under neutral and basic conditions was higher than that under acidic conditions. Metal ion Ca2+ was necessary for the maintenance of rcMMP-9 activity, whereas Zn2+ inhibited its activity. Our present study indicated that MMP-9 is responsible for the disintegration of intramuscular connective tissues by cleaving type V collagen during postmortem tenderization of fish muscle. PRACTICAL APPLICATION: Elucidation the involvement of MMP-9 in collagen degradation will deliver a reference for the prevention of muscular protein decomposition during chilled storage of fish fillets.

Sustainable and inclusive development of finfish mariculture in Cambodia: Perceived barriers to engagement and expansion

Finfish mariculture, dominated by production of Asian seabass (Lates calcarifer), is of high economic importance in Cambodia and is providing substantial benefits to engaged communities in coastal areas. Using semi-structured face-to-face interviews, we explore perceived barriers to engagement in the industry in three coastal districts of Cambodia where such farming is undertaken. We explore obstacles faced by current finfish mariculture value chain actors, eliciting perceptions of 56 female and male current participants. We also elicit perceptions of the industry entry restrictions by interviewing 62 men and women in the same communities, but who are currently not engaged in finfish mariculture. Specifically including men, women, youths and religion in the study sample, we also tested for potential differences in perceptions of the barriers based on demographic characteristics. The most pertinent areas for strengthening the value chain were identified by participants as: Strengthening training and technical support services; Improving availability of good quality fingerlings; Promoting compounded feeds to replace ‘trash’ fish; and Supporting value chain inclusivity, development and diversification. The most common obstacles to entry into the industry were reported as lack of: Finance and financial support; Security of access to land and water; Technical support services and experience; and Time and available labour. Barriers and participant needs identified in this study indicate a set of emerging priorities for both the Cambodian Fisheries Administration and the international donor community.

Effect of Vitamin B Complex and Phosphorus on Stress Resistance and Phosphorus Uptake in Barramundi

Barramundi, the Asian sea bass (Lates calcarifer Bloch 1790), is a valuable aquaculture commodity, but seed survival is generally low. This study used a completely randomized design (two factors; 16 treatments; 3 replicates) to examine the effect of adding vitamin B complex and phosphorus to the rearing media on the survival, stress resistance, and phosphorus content of barramundi larvae. Barramundi larvae aged two days were stocked at a density of 25 fish L-1 in 40 L green plastic basins (30 L water) and reared for 30 days with natural feed (Chlorella and rotifers). The factor I was vitamin B complex with 4 levels: 0, 75, 150, and 225 mg L-1. Factor II was phosphorus with four levels: 0, 0.5, 1.0, and 1.5 mg L-1. Commercially available B vitamin complex and phosphorus mineral supplements were dissolved in water and added to the larval-rearing media. Analysis of variance showed that the combination of vitamin B complex and phosphorus treatments had a significant effect (P &lt; 0.01) on survival, stress resistance, and phosphorus uptake. Survival and phosphorus content in barramundi larvae were highest with a combination of 150 mg L-1 vitamin B complex and 1.0 mg L-1 phosphorus and lowest in control (0 mg L-1 of both additives).

Substituting fish meal with a bacteria protein (Methylococcus capsulatus, Bath) grown on natural gas: Effects on growth non-specific immunity and gut health of spotted seabass (Lateolabrax maculatus)

This study aimed to evaluate effects of substituting fish meal (FM) by methanotroph (Methylococcus capsulatus, Bath) bacteria meal (FeedKind®, FK) on growth performance, non-specific immunity and gut health of Lateolabrax maculatus. Six iso-nitrogenous diets were formulated with 0, 3.5%, 7%, 10.5%, 14% and 17.5% FK to substitute 0 (control group, FM content: 35%), 10%, 20%, 30%, 40% and 50% fish meal, referred to as FM, FK3.5, FK7, FK10.5, FK14, and FK17.5 respectively. Fish (initial body weight: 11.00 ± 0.02 g) were fed experimental diets for 56 days. Results showed that growth of fish fed the FK3.5 diets was significantly increased (P < 0.05) but that there was no significant difference (P > 0.05) in growth of the other groups (FK7-FK17.5) compared with control group. Although survival of fish in the 50% substitution group was significantly decreased (P < 0.05) compared with the other groups, there was no overall trend in the survival data. The activities of serum acid phosphatase (ACP), alkaline phosphatase (AKP), gut lipase and protease and the contents of serum total protein and albumin in the FK3.5 group were significantly higher than those of control group (P < 0.05). In contrast, the activities/contents of serum ACP, AKP, lysozyme and complement 4 in the FK10.5, FK14 and FK17.5 groups were significantly decreased compared with control group. There was no significant difference in gut mucosal structure among all groups. The analysis of gut flora showed that the relative abundance of Lactobacillus in the FK7 and FK10.5 groups was significantly higher than other groups. In conclusion, dietary FK inclusion level up to 14% of total diet to replace 40% FM is possible without negatively affecting the growth performance of spotted seabass. Furthermore, the replacement of FM with 3.5% FK enhances the growth and immune, and substituting 20–30% of FM by 7–10.5% FK increased the abundance of beneficial bacteria in intestine of fish.