Pikeperch (Sander lucioperca) is a species with great potential for aquaculture in Eurasian countries, while feed costs limit the scale of pikeperch farming. Adding carbohydrates to the feed as an energy source is a viable approach to reduce costs and to improve the culture status of pikeperch. In this study, in order to determine the optimal carbohydrate requirement of pikeperch, three tapioca starch (8%, 10%, and 12%) added feeds were produced with isonitrogenous (51%) and isolipidic (11%). For 8 weeks, body weight was 1.20 ± 0.01 g, pikeperch were manually fed the trio of experimental diets until they seemed fully satisfied. The finding revealed that pikeperch can utilize dietary carbohydrate, but excessive dietary carbohydrate will adversely affect the growth performance. The growth and survival rate were decreased in pikeperch in S12 (P < 0.05). The α‐amylase activity of S12 reduced in the intestine and lipid deposition was observed in the liver compared with the S8. In addition, proinflammatory cytokines, interleukin 1 beta (il1-β), interleukin 8 (il8), and tumor necrosis factor beta (tnf-β), in the liver and intestine elevate and anti‐inflammatory cytokines, interleukin 10 (il10) and transforming growth factor beta (tgf-β), decrease with increasing dietary carbohydrate levels. Hepatic and intestinal antioxidant capacity were also adversely affected, with S12 significantly increasing malondialdehyde (MDA) contents and decreasing glutathione (GSH) and total antioxidant capacity (T‐AOC) (P < 0.05). The intestinal barrier function is also damaged, the height and width of intestinal villi decreased, and the expression of occludin-a, occludin-b, and zonula occludens‐2 (zo-2) genes was decreased. Elevated levels of starch intake led to harm to gut microflora, reducing bacterial populations, simultaneously boosting the presence of detrimental bacteria (Proteobacteria, Actinobacteriota, Achromobacter, and Rhodococcus) and diminishing the beneficial bacteria (Firmicutes). In conclusion, moderate addition of starch as an energy source can reduce feed costs; however, over addition can bring about organism damage and is recommended to be added at less than 10%.

Perca fluviatilis is an economically important species of freshwater fish. To understand the genetic structure of P. fluviatilis in China, 268 samples were collected from Wulungu Lake (WL), Jili Lake (JL), the Wulungu River (WR), and the Kalaeerqisi River (KR). These samples were then analyzed using microsatellite markers. A total of 98,425 microsatellite markers were developed based on the genomic data, and 29 polymorphic microsatellite markers were selected to analyze genetic diversity in this study. The number of alleles (N_a) and observed heterozygosity (H_o) per population ranged from 4.621 (KR) to 11.172 (WL) and from 0.510 (KR) to 0.716 (JL), respectively. The results of the polymorphic information content (PIC) showed that the WL, JL, and WR populations were highly polymorphic (PIC≥ 0.5) and that the KR population was moderately polymorphic (0.25 ≤ PIC < 0.5). The genetic differentiation coefficient (F_st) among the four P. fluviatilis populations was 0.074, indicating moderate genetic differentiation among the populations in Xinjiang. The reason for the significant difference between the rivers and lakes could be the presence of a dam blocking the flow of P. fluviatilis. The development of microsatellite markers provides support for population genetics in the future. The evaluation of the genetic structure of P. fluviatilis in Xinjiang provides a reference for the reproduction and conservation of P. fluviatilis.

Goldfish (Carassius aurautus), which is a middle size cyprinid, widely distribute throughout Eurasia. Phylogeographic studies using mtDNA markers have revealed several divergent lineages within goldfish. In this study, mtDNA variations were determined to elucidate the phylogeographical pattern and genetic structure of goldfish in Northeast Asia. A total of 1054 individuals from Amur river basin were analyzed, which including five newly collected populations and four previously reported populations. Three distinct mtDNA lineages were identified in those samples, two of which corresponded to two known lineages C2 and C6, respectively. The third lineage referred to as C7, following six known lineages of goldfish in mainland Eurasia. AMOVA results suggested that most of the genetic variations were among lineages, rather than among populations or twice samplings. We noted that the control region (CR) and cytochrome b (cytb) sequences of lineage C7 have been reported in previous studies, respectively. However, the evolutionary position and distribution pattern of this lineage was not discussed in the context of the species. Our results showed that “odd” CR and “hidden” cytb sequences from Central Asia represent the same mtDNA lineage of goldfish. The known samples of C7 lineage were collected from Central Asia (Eastern Kazakhstan and Western Mongolia) to East Asia (Northeast China and Far East Russia), which suggested that it had a wider distribution, rather than limit in Central Asia.

The aim of this study was to investigate the impact of varying levels of defatted mealworm as a substitute for fish meal on the growth, intestinal health, and intestinal microflora of juvenile pikeperch ( Sander lucioperca ). Juveniles were fed diets containing 54% protein and 12% lipid over an 8‐week period, with defatted mealworms replacing 0%, 25%, 50%, 75%, and 100% of fish meal, respectively (designated as MW0, MW25, MW50, MW75, and MW100). The results showed that the MW25 group achieved the highest weight gain rate and specific growth rate, with no significant difference from the MW0 group. Moreover, the MW25 group exhibited the lowest feed conversion ratio. This group also exhibited the highest trypsin activity, whereas lipase activity showed no significant variation across all treatment groups. Intestinal villus height and width were not significantly affected by mealworm inclusion. These findings suggest that the inclusion of mealworm did not impact the digestive and absorptive capacity of the pikeperch intestine. However, gene expression related to growth ( ghr , igf1 , igf2 ) showed a consistent decline as mealworm inclusion increased ( p < 0.05). The expression of il10 was highest in the MW25 group ( p < 0.05), whereas il-1β and tgf-β expressions peaked in the MW50 group. Additionally, increasing mealworm levels led to a reduction in intestinal microflora diversity and abundance, with a decreased presence of Staphylococcus and Lactobacillus , which negatively affected the intestinal microflora structure. In conclusion, replacing no more than 25% of fish meal with mealworm is recommended to optimize growth performance and preserve intestinal microflora structure in juvenile pikeperch.