Background: The recirculating aquaculture system (RAS) is a widely used, water‐saving and efficient aquaculture model. However, bacterial diseases are common in farmed fish reared at high densities. Although antibiotics effectively treat these diseases, developing efficient methods to increase drug clearance in fish and decrease the concentrations of antibiotic residues in aquatic products is essential.Objectives: This study evaluates the effect of flowing water in the RAS on norfloxacin (NOR) pharmacokinetics in channel catfish (Ictalurus punctatus).Methods: Channel catfish were randomly divided into the control group (RAS group) and the experimental group (flow‐through aquaculture system group) (120 individuals/group). A NOR dose of 20 mg/kg was then orally administered to the fish. Plasma, muscle, liver and kidney samples were collected up to 168 h after treatment. NOR concentrations were measured using liquid chromatography–mass spectrometry, and pharmacokinetic parameters were calculated using a non‐compartmental method.Results: Flowing water had a significant effect on the plasma pharmacokinetics and tissue distribution of NOR, increasing NOR clearance in the kidney, muscle and plasma. The time to maximum concentration of NOR was shorter in the plasma and longer in the kidney and liver. Moreover, flowing water increased the maximum concentration of NOR in the kidney, muscle and plasma and decreased the area under the concentration–time curve from time 0 to the last measurable concentration in the liver and plasma. Flowing water decreased the withdrawal period in muscle from 10 to 6 days.Conclusions: These results indicate that flowing water can potentially increase NOR clearance in channel catfish.

Background: Red swamp crayfish (Procambarus clarkii) is one of the most economically important farmed aquatic species in China. However, it is also a famous invasive species in the world. Methods: The present study simulated near current (1970-2000) and future (2030s, 2050s) suitable distribution areas of P. clarkii aquaculture in China under 4 climate scenarios (SSP126, SSP245, SSP370 and SSP585) and screened out the dominant factors affecting the distribution as well, using the MaxEnt model with 60 effective distribution points. Result: The results showed that mean AUC was 0.986, which indicated a better forecast. The highly suitable aquaculture areas for crayfish were Hubei, Hunan, and Anhui Province. The important environmental factors affecting the distribution of P. clarkii were mean temperature of warmest quarter, precipitation of wettest quarter, isothermality and temperature seasonality. Compared to the present-day predictions, the total area of suitable distribution (general-, medium- and high-suitability) gradually increased in the 2030s and 2050s. The ranking of the total area under different climate change scenarios were SSP370 greater than SSP585 greater than SSP126 greater than SSP245 in the 2030s and SSP585 greater than SSP370 greater than SSP126 greater than SSP245 in the 2050s, indicating that as the greenhouse gas emissions increase, the distribution of P. clarkii was likely to increase. It was of note that the area of high-suitability distribution for SSP585 greatly increased, but for SSP245 greatly decreased in the 2050s. This suggested that we should attach great importance to the ecological risk of crayfish in China and prevent the blind development of the industry.

A method was developed for the determination of chlorpyrifos residues in paddy field aquatic products by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples were extracted with acetonitrile and purified by using 0.2 g primary secondary amine (PSA) sorbent and 1.2 g MgSO4. The target compound was separated on a Hypersil GOLD C-18 column (100 mm x 2.1 mm, 5 mu m), and was determined using a heated electrospray ionization (HESI) source in the positive ion selective reaction monitoring (SRM) mode. The analyte was quantified with external standard using the matrix. matched standard cal. ibration curve method. The results showed that good linearities were obtained in the range of 0.5-100.0 mu g/L, and the correlation coefficients were greater than 0.999. The spiked recover. ies of chlorpyrifos ranged from 86.2% to 103.6% with RSDs of 3.5%-7.6% (n = 6). The limits of detection and quantification were 0.25 mu g/kg and 0.5 mu g/kg, respectively. This method is simple, quick, sensitive, and suitable for the rapid determination and analysis of chlorpyrifos residues in paddy field aquatic products.

Chinemys reevesii, a special economic aquaculture species in China, is valued highly for its medicinal and nutritional benefits. However, the muscle of farmed C. reevesii exhibits a strong off‐flavor, resulting in poor flavor quality. To enhance the flavor quality of the C. reevesii meat, this study examined the volatile compounds in C. reevesii muscle by establishing identification methods for these volatile odor compounds and comparing the differences between the two aquaculture modes. It also explored the impact of fasting temporary rearing (60 days) on the flavor quality of the C. reevesii meat. The results indicated that a combination of direct solvent extraction‐solvent‐assisted flavor evaporation (DSE‐SAFE), headspace‐solid phase microextraction (HS‐SPME), gas chromatography–mass spectrometry/olfactometry (GC–MS/O), and aroma recombination effectively simulated the odor profile of C. reevesii meat. The study identified the key volatile odor compounds in outdoor pond‐cultivated C. reevesii meat (OP), including hexanal, heptanal, 1‐octen‐3‐ol, octanal, nonanal, (E)‐2‐nonenal, decanal, (E)‐2‐decenal, (E,E)‐2,4‐decadienal, and dodecanal. In greenhouse‐cultivated C. reevesii meat (GH), key volatile odor compounds were hexanal, hexanol, heptanal, 1‐octen‐3‐ol, octanal, nonanal, (E)‐2‐nonenal, decanal, (E)‐2‐decenal, and dodecanal. The study found that appropriate fasting temporary rearing improved the odor quality of C. reevesii meat; OP temporary rearing for 40–50 days showed a significant reduction in greasy and musty odors. In GH, 40 days temporary rearing retained a fresh aroma while reducing the seaweed and fishy odors, achieving a flavor similar to OP. This study provides data support for C. reevesii meat processing and suggests a reference for applying temporary rearing to enhance the flavor quality of aquatic products.

Background: Chinese pond turtle (CPT, Mauremys reevesii) is a typical species with temperature-dependent sex determination (TSD). Pond slider turtle (PST, Trachemys scripta) is considered one of the worst invasive species in the world. In order to analyze the adaptive evolution of fecundity traits in CPT and TSD, the rapidly evolving gene families were obtained and functional enrichment analysis was performed. At the same time, CPT and PST species-specific genes were also enriched for their fecundity traits. Methods: Orthofinder software was employed to search homologous genes based on protein sequence. CAFÉ software was used to obtain the expansion and contraction gene families of CPT and PST. Then, GO terms and pathway enrichment analyses were performed using TBtools software and Swissprot database. Result: In CPT, 159 rapid expansion gene families GO enrichment results showed that the reproductive activities related pathways were mainly three significant enrichment process, spermatogenesis, steroid hormone mediated signaling pathway and male gamete generation. 2 rapidly contraction gene families showed that there was no significant enrichment pathway related to reproduction. The pathway of significant enrichment were RNA biosynthetic process, regulation of RNA metabolic process and regulation of cellular metabolic process. The gene families unique to the species were significantly enriched in pathways DNA replication-dependent nucleosome organization, DNA replication-dependent nucleosome assembly and negative regulation of megakaryocyte differentiation. In PST, 15 rapid expansion gene families GO enrichment results showed that the most significant GO terms mainly consisted of biological processes which were involved in endocrine process, regulation of endocrine process and cellular response to steroid hormone stimulus, but spermatogenesis and male gamete generation gene families also expanded. 58 rapidly contraction gene families showed that the pathways of significant enrichment were endocrine process, cellular response to steroid hormone stimulus and regulation of endocrine process. At the same time, estrogen secretion, binding of sperm to zona pellucida and sperm-egg recognition gene family also rapidly contraction. The gene families unique to the species were significantly enriched in pathways adenylate cyclase-activating G protein-coupled receptor signaling pathway, double-strand break repair and regulation of potassium ion transport.