Our study investigated the effects of dietary arginine supplementation on the growth performance, antioxidant capacity, intestinal digestive enzyme activity, muscle transcriptome, and gut health of Chinese perch (Siniperca chuatsi). Four isonitrogenous and isolipidic diets (50% crude protein, 11% crude lipid) with graded levels (2.61%, 2.99%, 3.37%, and 3.82%) of arginine were formulated and processed. A total of 360 Chinese perch (approximately 45–46 g) were randomly divided into four groups with triplicates of 30 fish per cage in each group. Our results revealed that although there was no significant improvement in the growth performance of Chinese perch, their antioxidant capacity and nutritional metabolism were significantly improved. Compared to the control group (without arginine supplementation, 2.61% group), feeding graded arginine levels could significantly (P < 0.05) decrease serum glucose and malondialdehyde (MDA) contents, as well as increase total superoxide dismutase (TSOD) activity. Fish fed a 3.37% arginine diet had the highest TSOD activity in the serum and liver. The intestinal morphological structure was clearer and more uniform in the 2.99% and 3.37% arginine groups. Fish fed with 3.82% arginine had significantly decreased (P < 0.05) muscle valine, glutamate, tyrosine, and total non-essential amino acid contents, with decreased (P < 0.05) intestinal amylase activity. Transcriptome analysis showed that graded arginine levels significantly (P < 0.05) influenced muscle gene expression involved in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of energy metabolism (amino acid, glucose, fatty acid), signaling pathways (mTOR, PI3K-Akt, MAPK, foxO, and insulin pathway), etc. The microbial community structure did not change significantly. Mycoplasma showed the highest abundance in the control group, and Cetobacterium had the highest abundance in the dietary arginine supplementation groups. Network analysis showed that the network complexity of the control group was higher than those of arginine groups. Our finding would help advance the field of arginine nutrition and guide the development of future fish feeds. Based on antioxidant and intestinal health indicators, the optimal dietary arginine requirement for Chinese perch was 2.99%–3.37% of the dry diet (6.08%–6.79% of dietary protein).

The present study aimed to evaluate the feasibility of a formulated diet to replace live baits as feed for Siniperca chuatsi. A 2 × 2 factorial design with three replicates was used to investigate the effects of conventional live baits (LB) and a formulated diet (FD) on the growth, muscle nutrition composition, and digestive enzyme activities of S. chuatsi at two growth stages. The results showed that the feed conversion ratio (FCR) in the FD group was significantly lower than that in the LB group. The final body weight (FBW) and weight gain (WG) were not significantly different between the two feeding modes. However, at the juvenile stage, the specific growth rate (SGR) in the FD group was significantly lower than that in the LB group. Muscle moisture, crude protein, and crude lipid contents were not influenced by dietary treatments. There were no significant differences in ∑EAA, ∑NEAA, and ∑AA compositions of the juvenile and adult stages fed the two kinds of diets. At the juvenile stage, histidine (His) content in the FD group was significantly higher than that in the LB group; at the adult stage, cysteine (Cys) content in the FD group was significantly higher than that in the LB group; at both growth stages, Met content in the FD group was significantly lower than that in the LB group. The FD group showed higher levels of ∑SFA, ∑HUFA, ∑n-3PUFA, n-3/n-6, EPA, and DHA than the LB group did, whilst the opposite occurred in the MUFA levels. In addition, fish fed with LB had significantly higher values of pepsin and intestinal trypsin activities in the juvenile fish compared to the FD group, but the activities were not significantly different between the two feeding modes at the adult stage. The activities of stomach and intestine amylase in the FD group were significantly higher than those in the LB group. Overall, these results showed that under long-term feeding conditions, S. chuatsi fed with the artificial diet had no significant difference in muscle crude protein, crude lipid, amino acid composition, and digestive capacity, but showed superiority in the composition of fatty acids such as EPA and DHA levels compared to the live baits group. Therefore, the artificially formulated diet might be a more appropriate feeding approach for sustainable development of the S. chuatsi industry.

An 8-week feeding experiment was conducted to evaluate the effect of dietary protein to lipid ratio on fish growth performance, digestive enzyme activity, body composition, serum biochemistry, immunity, and antioxidant capacity of Carassius auratus var. Pengze juveniles. Nine experimental diets were formulated in a 3 × 3 factorial design to contain three protein levels (30%, 35%, and 40%) and three lipid levels (5%, 8%, and 11%), with protein-to-energy (P/E) ratios ranging 19.2–27.1 mg/kJ and named as Diet 1 (30/5), Diet 2 (30/8), Diet 3 (30/11), Diet 4 (35/5), Diet 5 (35/8), Diet 6 (35/11), Diet 7 (40/5), Diet 8 (40/8), and Diet 9 (40/11), respectively. Each diet was randomly assigned to triplicate groups of 20 fish per cylindrical fiberglass tank. The fish fed with Diet 4 had the highest specific growth rate (SGR) among the 9 groups. The whole-body lipid content increased significantly with increasing dietary lipid levels regardless of dietary protein content ( P < 0.05 ), whereas moisture content showed an opposite trend ( P < 0.05 ). The highest values of activities of serum lysozyme (LZM) and alkaline phosphatase (AKP) were detected in the fish fed Diet 4 (35/5), whereas malondialdehyde (MDA) was lowest in the fish fed Diet 4. In addition, serum total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) were the lowest, while high-density lipoprotein (HDL-C) and high-density lipoprotein to total cholesterol ratio (HDL-C/TC) were the highest in the Diet 4 group. The results indicate that a combination of 35.1% protein and 5.1% lipid with dietary CP/GE (mg/kJ) ratio of 24.0 is optimal for the culture of Carassius auratus var. Pengze juveniles.

This trial aimed to investigate the influence of graded replacing fish meal (D1: 0.00%, D2: 27.27%, and D3: 54.55%) with mixed protein ingredients (i.e., chicken meal, krill meal, fermented soybean meal, and soy protein concentrate) on the growth performance, muscle nutritional composition, blood biochemical indices, gut bacterial community, and transcriptome of Chinese perch. Two hundred seventy Chinese perch were divided into three groups (90 per group) and the diet lasted for 56 days. Results showed that the weight gain rate and specific growth rate were significantly lower, and the feed conversion ratio was significantly higher in the D3 group than in fish fed D1 ( ), with no significant differences between the D1 and D2 groups ( ). The muscle crude protein content was highest in the D2 group, and the crude fat content was significantly different in the order: D3 > D1 > D2 ( ). The levels of serum triglycerides (TG) and low-density lipoprotein cholesterol in the D2 group were significantly lower than those in the D1 group ( ), but there was no significant difference compared to the D3 group ( ). The microbial community structure changed significantly. Mycoplasma showed the highest abundance in the D1 and D2 groups ( ), and Cetobacterium peaked in D2 group, and significantly higher than that in D1 group ( ). Network analysis and cohesion index calculation showed that both network complexity and cohesion peaked in D2 group, and Cetobacterium was highly correlated with the cohesion index ( ). Further, muscle transcriptome analysis results showed that compared with the control group, differentially expressed genes were clustered (Q < 0.05) in the arginine and proline metabolism pathways in D2 group. Fish in D3 group significantly (Q < 0.05) affected genes involved in KEGG pathways of ribosome, circadian rhythm, thermogenesis, insulin signaling pathway, fatty acid degradation, oxidative phosphorylation, and apoptosis. In conclusion, under the experimental conditions, the replacement of 27.27% of fish meal by the compound protein did not have a negative impact on the growth performance of Chinese perch and could improve muscle quality, lipid metabolism, and the interaction of intestinal microbiota.

Farming Chinese perch in aquaculture systems with artificial diets is a new method and developing trend. This method of raising Chinese perch has led to outbreaks of new diseases. In 2022, a disease outbreak occurred among farmed Chinese perch fed an artificial diet in Jiangxi Province, China, during which 50% of the fish died. The clinical signs exhibited by the diseased Chinese perch included decreased physical vitality, anorexia, emaciation, and dorsal fin ulceration with white cysts and flocs. Coinfection with ciliate parasites and an oomycete was found. No pathogenic bacteria were isolated from the microbial test, and the viral detection results were negative. After morphological and 18S or 28S rDNA sequence clustering analysis, the parasites were identified as Epistylis wuhanensis and Zoothamnium sp., while the oomycete was identified as Achlya klebsiana. This article discusses the interaction between parasitic and oomycete coinfections in Chinese perch from the perspective of the characteristics of Chinese perch raised with an artificial diet. The relationships between parasites, oomycete, and fish were also briefly discussed. This is the first report of the coinfection of Chinese perch with Epistylis wuhanensis, Zoothamnium sp. and Achlya klebsiana.

A new species of the spiny loach genus Niwaella is described herein from the Xiu-Shui river, an affluent of Lake Poyang in Jiangxi Province, China. This species is distinguished from all other congeneric species in China due to having a unique body coloration, comprising 20-25 transverse black bars on the dorsum and upper part of the flank. Other characteristics, though not exclusive to this species, include an indistinct blackish mid-dorsal stripe from the nape to the caudal-fin base, a lower jaw fully covered by the lower lip; 17-20 black vertical bars on the lower part of flank, a short suborbital spine with a shorter processus latero-caudalis that is less than one-fifth the length of the processus medio-caudalis, and seven branched dorsal-fin rays. The validity of the new species is corroborated by its monophyly, as evidenced by phylogenetic analysis based on the mitochondrial cytochrome b gene.