Effects of delayed feeding on growth and survival of Channa striatus (Bloch) larvae

Abstract. Newly hatched Channa striatus (Bloch) were tested for survival and growth under various delayed feeding regimes. Channa striatus larvae were found to be extremely tolerant to the delay in initial feeding. About 9% of the larvae died when initial feeding was delayed by 2 days after yolk absorption. However, mortality progressively increased with further delays in first feeding. Only 26% of larvae took food when it was offered 11 days after yolk absorption.'Point of no Return'was reached only on the 14th day of starvation.     

Dietary supplementation of L-tryptophan: Effect on growth and survival of Pabda,Ompok bimaculatus (Bloch) fry

ABSTRACT

A 30-day experiment was conducted to assess the effect of tryptophan-supplemented diets on growth and survival of Pabda, Ompok bimaculatus fry. Fifty pabda fry (0.114 ± 0.02 g; 2.45 ± 0.13 cm) were stocked into each aerated aquarium following a completely randomized design consisting of four treatments with triplicate each. Four iso-proteinious purified diets were prepared with different levels of tryptophan—0%, 1%, 2%, and 3%—of the dry diet and were designated as Control, TRP1, TRP2, and TRP3 respectively. Fishes were fed with the experimental diet ad libitum four times a day. The results showed that fish fed with tryptophan-supplemented diets exhibited significantly (P < 0.05) lower cannibalism and higher survival than the control diet. Further, the tryptophan-supplemented groups showed a significantly lower coefficient of variation (%) and size heterogeneity (P < 0.05). However, the growth as measured by body weight gain, length increment, and specific growth rate of fry in tryptophan-supplemented groups was significantly lower than the control group (P < 0.05). Moreover, maximum survival (52.67 ± 1.76%) and minimum cannibalism (21.33 ± 5.70%) coupled with higher growth and performance index (0.38 ± 0.01) were recorded in the 2% tryptophan-supplemented group compared to other tryptophan-fed groups. Overall interpretation from the present study concludes that the dietary supplementation of 2% tryptophan is recommended for better survival of pabda fish, although growth was compromised.     

Influence of dietary lipid/protein ratio on survival,growth, body indices and digestive lipase activity in Snakehead (Channa striatus,Bloch 1793) fry reared in re‐circulating water system

Nine isoenergetic (18.5 kJ g^?1) diets were formulated in a 3 × 3 factorial design to contain three protein levels (350, 400 and 450 g kg^?1) for each of three lipid levels (65, 90 and 115 g kg^?1), respectively, and fed twice daily for 8 weeks to fish of mean initial weight 3.34 ± 0.02 g reared in a re‐circulatory water system. Temperature, pH and dissolved oxygen (DO) were maintained within the range 28–30 °C, 5.6–6.8 and 4.82–6.65 mg L^?1 respectively throughout. Results show that fish survival was better in the groups fed 65 g kg^?1 lipid while growth performance (% weight gain, WG; specific growth rate, SGR) and nutrient utilization (feed conversion ratio, FCR; protein efficiency ratio, PER; protein intake, PI) in the 65/450 and 90/450 g kg^?1 treatments were similar and significantly (P < 0.05) higher than in fish fed the other lipid/protein ratio combinations. The body indices monitored (Hepatosomatic index, HSI and viscerosomatic index, VSI) were similar among the treatments whereas intestinal lipase activity was not significantly (P < 0.05) affected by increase in dietary lipid and protein levels. Carcass composition showed that dietary protein level affected body protein content positively in the 65 and 90 g kg^?1 lipid treatments, but dietary lipid level did not affect body lipid content. A lipid/protein ratio of 65/450 g kg^?1 is considered adequate for good growth performance and survival of Channa striatus fry.     

Maximum handling size,prey size and type selection by snakehead (Channa argus) feeding on juvenile Chinese mitten crab (Eriocheir sinensis)

Laboratory predation trials were conducted to investigate maximum handling size, prey size and type selection by small (35–37 cm in total length, L_T), medium (43–46 cm L_T) and larger (58–60 cm L_T) snakehead (Channa argus) when feeding on a wide size (9–34 mm in carapace width, C_W) range of juvenile Chinese mitten crab (Eriocheir sinensis). The maximum handling size of predator feeding on crabs monotonically increased with predator L_T and mouth gape width, G_W. Snakehead with at least 16.0 cm L_T or 27.7 mm G_W would be capability to consume the smallest size group of crabs, whereas the predator with 72.6 cm L_T or 63.4 mm G_W would be capability to consume all size groups of crabs in these trails. Prey‐size selection trials showed that snakehead has a high preference to the small‐sized crabs, and lower preference to the medium or large size crabs. The preference index was significantly affected by prey size and prey size × predator size interaction, however, was not affected by predator size. In prey type experiments, snakehead consumed lower proportions of juvenile crabs when fed on the crab and crucian carp than when fed on only the crab, which suggests alternative fish prey may reduce predation risk of the crab by snakehead in nature. These results could be useful for improving the fishery management and release strategies for the crab.     

Effects of multienzyme complex and probiotic supplementation on the growth performance,digestive enzyme activity and gut microorganisms composition of snakehead (Channa argus)

The major objective of this study conducted for 7 weeks was to investigate the influence of supplementation with multienzyme complex and probiotic and their interaction effects on the growth performance, body composition, serum biochemical parameters and gut microorganism composition of snakehead (Channa argus). There were four treatments in this experiment coded as control, probiotic (Bacillus amyloliquefaciens), multienzyme (amylase, acid protease and papain) and pro‐multi (B. amyloliquefaciens and amylase, acid protease and papain), respectively. The results demonstrated that snakeheads on the multienzyme resulted in better growth performance in terms of final body weight (FBW), weight gain ratio (WGR) and feed conversion ratio (FCR) significantly (p < 0.05) than those on the control diet, while they did not (p > 0.05) on probiotic and pro‐multi. Snakeheads receiving multienzyme increased significantly (p < 0.05) the serum parameters, including albumin, total protein and AKP and probiotic increased AKP and lysozyme meanwhile decreased the LDL‐C significantly (p < 0.05) compared with control. Analysis of the composition of gut microorganisms showed that four dominant microorganisms were Spirochaetes, Proteobacteria, Firmicutes and Bacteroidetes. Probiotic could enhance the richness and diversity of gut microorganisms in snakeheads, furthermore revealing a means of evaluating the relationship between feed supplementation and microorganisms.     

Growth and production performance of threatened snakehead fish,Channa striatus (Bloch), at different stocking densities in earthen ponds

Production trials of threatened snakehead fish (Channa striatus) were carried out under different stocking densities in earthen ponds of Bangladesh. The average weight and length of the fingerlings during stocking was 17.63 ± 1.23 g and 13.21 ± 0.52 cm. Fingerlings were stocked at 5000 ha^?1 in treatment‐1 (T₁), 6250 ha^?1 in treatment‐2 (T₂) and 7500 ha^?1 in treatment‐3 (T₃) respectively. Fish in all the experimental ponds were fed with supplementary feed comprising of fish meal (30%) and mustard oilcake (70%) at the rate of 3–6% of estimated body weight two times per day. In addition, trash fish were supplied at the rate of 2–3% of the estimated biomass on each alternate day. In situ water quality parameters of the pond were within the suitable range for fish culture. The growth and survival of fingerlings were significantly higher in T₁ than in T₂ and T₃. The food conversion ratio was significantly lower (P<0.05) in T₁ than in T₂ and T₃. The estimated gross and net production of fish was higher in T₁, followed by T₂ and T₃. Overall, the highest growth, survival and production were obtained from T₁. Therefore, it could be concluded that of 5000 fingerlings ha^?1 is the most suitable stocking density for culturing C. striatus under a monoculture system in the earthen ponds for better production.     

Evaluation of dietary vitamin E supplementation on growth performance and antioxidant status in hybrid snakehead (Channa argus × Channa maculata)

An 8‐week feeding trial was conducted to investigate the effects of dietary vitamin E on growth performance and antioxidant status of juvenile snakehead. The snakeheads (20.47 ± 0.06 g) were fed with five isonitrogenous and isoenergetic experimental diets that contained 13 (the basal diet), 52, 79, 168 and 326 mg of vitamin E kg^?1, respectively. The maximum specific growth rate (SGR) and feed intake (FI) were achieved in fish fed on a diet with 79 mg kg^?1 vitamin E (p < .05). No significant differences were found in protein efficiency ratio (PER), feed conversion ratio (FCR) and survival of fish among all groups (p > .05). Vitamin E supplementation improved hepatic glutathione peroxidase (GPx) activity significantly. A consistent decline in the hepatic and serum malondialdehyde (MDA) content was observed in fish fed diets with the increased supplementation of vitamin E (p < .05). In addition, with the increasing level of vitamin E, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were reduced (p < .05). However, serum superoxide dismutase (SOD), catalase (CAT) and alkaline phosphatase (ALP) activities were enhanced in fish fed 79 mg vitamin E kg^?1 diet and then decreased significantly as the content of vitamin E in the diet increased (p < .05). Meanwhile, serum albumin (ALB) and globulin (GLB) were not affected by the supplemental levels of dietary vitamin E (p > .05). The vitamin E concentrations in liver and serum increased significantly with increasing dietary vitamin E (p < .05). Based on the broken‐line regression of SGR, vitamin E level in the diet is estimated to be 80.5 mg kg^?1 for Channa argus × Channa maculata. In conclusion, this study indicated that the dietary appropriate vitamin E could enhance the growth performance, antioxidant status and non‐specific immune response.     

Histopathology of snakehead, Channa striatus (Bloch), experimentally infected with the specific Aphanomyces fungus associated with epizootic ulcerative syndrome (EUS) at different temperatures

Abstract Snakeheads, Channa striatus (Bloch), were inoculated with a spore suspension of the specific pathogenic Aphanomyces , isolated from fish affected by epizootic ulcerative syndrome (EUS), in South East Asia. Fish were held at three different temperatures: 19, 26 and 31 °C. Histological changes induced by the infection are described. In the early stages of the disease, degenerative changes were observed in all samples, but inflammatory infiltrate was much more marked in fish kept at 26 and 31 °C. By 8 days post-injection, extensive mycotic granulomatosis was observed in the samples kept at 26 and 31 °C. The fish kept at 19 °C developed a severe invasive myonecrosis with limited macrophage response. From 14 to 28 days post-injection, healing became well established at 26 and 31 °C and surviving fish kept at these temperatures recovered completely by 28 days. The lesion was still progressing at 21 days post-injection in fish kept at 19 °C, and all such fish succumbed by this time. Thus, mortalities in the fish kept at 19 °C were considerably higher than in the groups of fish kept at 26 and 31 °C. The findings help to explain why mortalities from EUS occur when water temperatures are low.     

Bioenergetics of cannibalism in juvenile barramundi Lates calcarifer (Bloch): exploring growth advantage of fish fed live prey and formulated diet

The present study investigated the growth performance of juvenile barramundi Lates calcarifer (Bloch) fed conspecific prey (CP), formulated diet (FD) and a mix of both (MIX) using a bioenergetics approach. Fish in the MIX treatment ingested significantly more CP than FD by dry mass. However, prey mass ingestion and cannibalism rate in the MIX treatment were significantly lower than in the CP treatment. This indicates that the provision of alternative food does not complete mitigate cannibalism, but it can significantly reduce cannibalism in barramundi. Fish in the FD treatment showed a significantly higher daily food intake than fish in the CP or MIX treatments. However, fish fed conspecifics showed significantly better feed conversion efficiencies, apparent digestibility rates and growth performances. Exclusive cannibalistic barramundi assimilated significantly more energy consumed, with 1.5% of energy lost in faeces comparing with 7.3% of siblings feeding exclusively on FD. Consequently, exclusive cannibals channelized more energy consumption into growth (57.1%) than those fed solely on FD (43.9%). Therefore, high energy allocation into growth promoted better feed conversion efficiency and growth performance of cannibalistic barramundi than siblings fed solely on FDs. This study implies that fast‐growing cannibals may continuously prey on slow‐growing conspecifics due to growth advantage through cannibalism. Therefore, size heterogeneity should be reduced at initial stocking and controlled as fish grow to avoid the emergence of new cannibals.     

Effect of triiodothyronine on the growth and survival of larval striped bass (Morone saxatilis)

This study was carried out to test the effect of triiodothyronine (T₃) on the growth and survival of larval striped bass (Morone saxatilis). Growth and survival of striped bass held in 5 ppt seawater and treated with various doses of T₃ were measured beginning at 5 and 16 days after hatching. Body content of T₃ was measured by radioimmunoassay. T₃ dissolved in the 5 ppt seawater was taken up by larval striped bass in a dose-dependent manner, and affected the growth and survival of the fish. At 5 days after hatching, T₃ at 100 ng ml^–1 and 50 ng ml^–1 retarded the growth of larval striped bass and caused a lower survival rate than T₃ at 25 ng ml^–1 or the control treatment. At 16 days after hatching, T₃ at 100 ng ml^–1 retarded the growth of larval fish and caused a higher mortality. T₃ at 10 ng ml^–1 and 1 ng ml^–1 did not show any effect on either survival or growth. Body content of T₃ returns to control levels within days following end of treatment. The results indicate that exogenous T₃ can be detrimental to the growth and survival of larval striped bass.     

复合蛋白源替代鱼粉对杂交鳢生长、体组成与生化指标的影响

为研究复合蛋白源替代鱼粉对杂交鳢生长、体组成、抗氧化与生化指标的影响,在基础饲料中用复合蛋白源(由棉粕+菜粕+蚕蛹+桑叶发酵而成)分别替代饲料中0%、12%、24%、36%和48%的鱼粉,配制成5种等氮等脂(含粗蛋白CP 42%,粗脂肪EE 8.5%)的实验饲料,在室内循环水族箱内饲喂杂交鳢(初始体质量22 g)8周。结果显示,当复合蛋白源替代鱼粉水平大于12%时,杂交鳢的终末体质量(FBW)和特定生长率(SGR)显著降低,在48%替代水平达到最低。36%和48%替代水平蛋白质效率(PER)显著降低,而饲料系数(FCR)显著升高。各实验组摄食率(FR)无显著差异。替代水平组全鱼粗脂肪含量以及脏体比(VSI)和肠脂比(IPF)显著降低,而水分含量显著增加。随替代水平的增加,胰蛋白酶活性显著降低,而肠脂肪酶活性显著升高。替代水平24%以上肝脏谷丙转氨酶(GPT)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性显著升高。替代水平12%以上血清中总胆固醇(CHO)含量显著降低,而替代水平36%以上血糖(GLU)含量会显著降低。各实验组血清甘油三酯(TC)、总蛋白(TP)和白蛋白(ALB)含量无显著变化。研究表明,复合蛋白源替代12%鱼粉不会影响杂交鳢的生长,而高水平替代会抑制杂交鳢的生长,但可以改善杂交鳢机体糖脂代谢,提高机体的抗氧化能力。     

Influence of different sources and levels of dietary protein and lipid on the growth,feed efficiency,muscle composition and fatty acid profile of Snakehead Channa striatus (Bloch, 1793) fingerling

Nine isoenergetic (18.5 kJ g⁻¹) diets were formulated, in a 3 × 3 factorial design, by varying three levels of dietary protein (350, 400 and 450 g kg⁻¹) at each of three levels of dietary lipid (65, 90 and 115 g kg⁻¹) accordingly. Each diet was hand fed two times daily for 8 weeks to triplicate homogenous groups of eight fish (average weight 3.34 ± 0.02 g) per tank connected to a recirculation system. Results showed that the feed efficiency and growth performance significantly (P<0.05) increased with increasing protein level at the two lower lipid levels (65 and 90 g kg⁻¹), respectively, as indicated by indices such as %weight gain, specific growth rate, protein efficiency ratio, feed conversion ratio and feed intake, but did not at the highest lipid level (115 g kg⁻¹). The muscle polyunsaturated fatty acids (PUFA) content declined with increasing dietary protein level at the lipid levels producing the highest growth, suggesting that the utilization of PUFA influences growth. Whereas the muscle monounsaturated fatty acids level was generally lower than the dietary levels in all the treatments tested, indicating preferential catabolism for energy, the muscle saturated fatty acids level was comparatively higher than in the diets, indicating selective deposition. Docosa hexaenoic acid (22:6n3, DHA), which was very low in the diet and in the initial fish, was higher in the muscle of some of the treatments, indicating the ability of Channa striatus to desaturate and elongate short‐chain PUFA to long‐chain HUFA, due to the availability of dietary 18:3n3 and 20:5n3 (the precursors for DHA biosynthesis). It could be concluded, based on the results of this trial, that a diet formulated to contain 65 g kg⁻¹ lipid and 450 g kg⁻¹ protein, with a gross energy of 18.5 kJ g⁻¹ and a dietary n3/n6 PUFA ratio of about 0.1, is sufficient to promote good feed efficiency and growth performance in C. striatus fingerling.     

Feeding interval and photoperiod influence the growth performance of striped knifejaw,Oplegnathus fasciatus

A two‐factor experiment incorporating two photoperiods (16 L:8 D and 24 L:0 D) and four feeding intervals (6, 9, 12 and 24 h) was carried out to determine the most efficient feeding interval and photoperiod for striped knifejaw, Oplegnathus fasciatus. Fish were fed a commercial diet to apparent satiation for 10 weeks. Blood was collected to measure the stress indicators. Both the photoperiod and the feeding intervals had a significant effect on the growth performance of striped knifejaw; however, their interaction did not produce any significant effect. The final body weight, weight gain (%) and feed intake at 6‐, 9‐ and 12‐h feeding intervals under 16 L:8 D were significantly higher than those at the 24‐h interval irrespective of the photoperiod (P<0.05). The specific growth rate at 6, 9 and 12 h intervals of the 16 L:8 D photoperiod was significantly higher than that of the other feeding intervals, except at 12 h of the 24 L:0 D photoperiod (P<0.05). At the end of the experiment, there were no significant differences in the plasma levels of cortisol, glucose and total protein observed in fish exposed to different photoperiods compared with the initial levels. The results suggested that a combination of a 16 L:8 D photoperiod and either of 6‐, 9‐ or 12‐h intervals can be used to stimulate the growth performance in striped knifejaw.     

Diet of non‐native northern snakehead (Channa argus) compared to three co‐occurring predators in the lower Potomac River,USA

Abstract – Introductions of large, non‐native, carnivorous fishes continue to occur worldwide and represent a substantial management concern to global biodiversity. One of the most recent non‐native fishes to successfully establish in North America is the northern snakehead (Channa argus), found in the lower Potomac River catchment. Dispersal of the northern snakehead throughout this system has been well documented since its original discovery in May 2004; however, little is known about the foraging habits of this species and its interactions with co‐occurring predators. Here, we quantify northern snakehead diet in comparison with the diets of naturalised largemouth bass (Micropterus salmoides), and native American eel (Anguilla rostrata) and yellow perch (Perca flavescens) collected from tidal freshwaters bordering Virginia and Maryland near Fort Belvoir, Virginia. Over 97% of northern snakehead gut contents were fishes, with fundulid and centrarchid species consumed most frequently. Dietary overlap was biologically significant only between northern snakehead and largemouth bass. Aquatic invertebrates were >10 times more common in native predator diets, reducing dietary overlap with northern snakehead. Ontogenic shifts in adult northern snakehead diet were also detected, which may be explained by optimal foraging rather than true prey specificity. Northern snakehead may be occupying a novel niche based on a piscivorous diet, therefore limiting competition with resident predators in the lower Potomac River. Further research into interactions between largemouth bass and northern snakehead is needed to inform management decisions and understand the ecological impacts of this non‐native species.     

Effects of substituting dietary fish oil with crude palm oil and palm fatty acid distillate on growth,muscle fatty acid composition and the activities of hepatic lipogenic enzymes in snakehead (Channa striatus,Bloch 1793) fingerling

Three diets were formulated to be iso‐nitrogenous (450 g kg^?1), iso‐lipidic (65 g kg^?1) and iso‐energetic (18.5 KJ g^?1), varying only in their lipid sources and designated as 100% fish oil (FO), 100% crude palm oil (CPO) and 100% palm fatty acid distillate (PFAD). Feed were hand fed to homogenous groups of 12 Channa striatus fingerlings (mean weight 3.5 ± 0.3 g) per tank in triplicate for 12 weeks, in a recirculation system. The growth performance and feed intake in the CPO and PFAD treatments were significantly (P<0.05) higher than those in the fish fed the control diet (FO), respectively, whereas the feed conversion ratio was better in PFAD than that in the other treatments respectively. The biological indices monitored (hepatosomatic index and viscerosomatic index) as well as carcass yield did not vary significantly among all the treatments respectively. The muscle fatty acid (FA) profile of fish was influenced by the composition of the diets fed, whereas no differences were recorded in the activities of the hepatic lipogenic enzymes monitored (fatty acid synthetase, citrate cleavage enzyme and malic enzyme). Whole‐body proximate composition analysis revealed that PFAD treatment, compared with others, contained significantly higher protein and ash, but lower lipid contents, although the muscle content of these nutrients was similar among all the treatments. Based on the results of this trial, CPO and PFAD could be used to partially substitute FO in the diet for C. striatus fingerling, to achieve good growth performance without any negative effects or compromising the muscle n‐3 FA composition (especially in the docosa hexaenoic acid and eicosa pentaenoic acid content).     

Effect of varying levels of dietary protein on the growth performance and feed conversion efficiency of snakehead Channa striata fry

Six isocaloric test diets, based on fishmeal-groundnut oil cake and containing 350–600 g kg^?1 protein at 50 g kg^?1 incremental levels were fed to snakehead, Channa Striata (Bloch), fry at a rate of 10% of body weight per day under laboratory conditions to determine the effect of varying level of dietary protein on the growth response. On the basis of percentage weight gain, daily weight gain, specific growth rate and daily tissue protein deposition, the dietary protein requirement of fry was found to be 550 g kg^?1 when fish meal was used as the major source of protein. There was a significant increase in carcass protein and a significant decrease in ash content with progressive dietary protein substitution. Fry fed with high protein diets tended to have lower carcass lipid contents and higher moisture contents.     

High density rearing of rohu,Labeo rohita (Hamilton) from spawn to fry in concrete tanks: effect of daily feed ration and soil base on fry growth and survival

Rearing of rohu spawn to fry size was carried out at high density (2000 spawn m^?2) in large concrete nursery tanks (10 m × 5 m × 1.2 m) to standardize the daily ration of supplementary feed and to assess the impact of soil base on the fry performance. In Set‐1, supplementary feed was provided at 100% (control), 75% and 50% of the daily ration that is commonly used in earthen carp nursery ponds and named as the three treatments T‐1, T‐2 and T‐3 respectively. Although in Set‐II, performance of fry were evaluated in tanks provided with and without soil base. The fry survival was to the tune of 45–59% at this high density of 2000 spawn m^?2, indicating the efficacy of the concrete nursery system for high density seed rearing. In Set‐I, T‐2 receiving 75% of the control ration exhibited similar fry growth as that of T‐1, but its fry survival (58.8%) was 10% higher than the latter. This indicated that supplementary feed in a concrete nursery can be reduced up to 25% of that provided in earthen nursery system while ensuring a higher fry yield. However, further reduction up to 50% of the control ration in T‐3 yielded lower fry survival and growth (P < 0.05) revealing inadequacy of the available feed. In Set‐II, treatment without soil base (T‐ns) yielded similar fry growth but 10% higher survival compared to that with the soil base (T‐s) revealing non‐essentiality of soil base in concrete tanks for such short‐term nursery rearing of rohu.     

Effect of dietary soybean meal associated with feeding time on the growth performance and intestinal microbiota composition of northern snakehead

A 63‐day growth trial was conducted with northern snakehead Channa argus to evaluate how rapidly its growth performance and how reproducibly its gut microbiota respond to different dietary protein sources. Four diets were formulated with different levels of soybean meal as a replacement for fishmeal (0%, 25%, 50% and 75%). Each diet was fed to three replicates of juvenile C. argus (30 juveniles per replicate, initial weight 8.65 ± 0.25 g) to produce groups G1, G2, G3 and G4 respectively. During this trial, survival rate, growth performance and intestinal microbiota composition were determined on days 9, 21 and 63. At day 9, there was no effect of the dietary soybean meal on the final weight (Wt), weight gain (WG) and specific growth rate (SGR) between the four groups (p > 0.05). However, at day 21 (p < 0.05), they were significantly lower in G4 fish than that in G1 and G2. The highest Wt, WG and SGR were found in G1 and G2 fish, the lowest growth was found in G4 fish at day 63 (p < 0.05). Furthermore, higher operational taxonomic units (OTUs) and alpha diversity were found in G4. With the dietary soybean level increased, the proportion of Firmicutes, Bacteroidetes and Verrucomicrobia, as well as some genera of bacteria (Carnobacterium, Cetobacterium, Planctomyces, Shewanella and Thermomonas) significantly increased in the G3 and G4 fish (p < 0.05). However, the OTUs, Chao index, and the proportion of Firmicutes and some genera (Acinetobacter, Bacillus and Geobacillus) in G4 fish were significantly higher at days 21 and 63 than that at day 9 (p < 0.05). Taken together, in response to dietary soybean meal levels, dynamic and significant changes in microbiota occurred, which then ultimately attained a new equilibrium.