中国水产科学研究院

Grass carp reovirus(GCRV)is a double-stranded RNA(dsRNA)virus that causes grass carp hemorrhagic disease(GCHD),resulting in substantial economic losses in aquaculture.Based on genomic and epidemiological cha-racteristics,GCRV strains are classified into three genotypes(GCRV-Ⅰ—Ⅲ),among which genotype Ⅱ(GCRV-Ⅱ)being the predominant causative agent of GCHD outbreaks.Although GCRV-Ⅱ strains share over 95%nucleotide and protein sequence similarity,they exhibit marked differences in virulence and pathogenic effects on host metabolism.This review summarizes recent advances in the molecular and epidemiological characteristics of GCRV-Ⅱ,highlights key findings on strains with varying virulence,and discusses progress in diagnostic techniques and vaccine develop-ment.Future research directions are proposed to facilitate effective prevention and control strategies for GCHD.

This study investigates the reproductive status and adaptive strategies of Coilia nasus in the Three Gorges Reservoir Re-gion(TGRR).A total of 388 specimens were collected from the core area of the TGRR(Wushan to Fuling section)between June and August of 2021-2023.Results indicate that the current age structure of the population is stable,with a female-to-male sex ra-tio of 0.92∶1 in the spawning cohort.The youngest sexually mature individuals were one year old for both sexes.The biological minimum size for females was 152.5 mm in body length and 11.96 g in body weight,compared to 166.6 mm and 17.64 g for males.The average absolute fecundity was(3.10±2.16)×104 eggs,and the average relative fecundity was(605.42±181.85)eggs/g.The average egg diameter was(615.47±107.30)μm,and the unimodal distribution of egg diameters indicated a single spawning strategy.The mean gonadosomatic index(GSI)was 6.32％±4.52％for females and 3.74％±1.63％for males,while the mean hepatosomatic index(HSI)was 1.15％±1.10％for females and 0.63％±0.53％for males.Compared to previous studies on C.nasus in the TGRR and other Yangtze River waters,the current spawning population exhibits a shift towards r-strategist charac-teristics,manifested as reduced egg size and increased absolute fecundity.In conclusion,the stable population structure and size of C.nasus demonstrate its successful adaptation to the TGRR environment.Its distribution is likely to expand further into other up-stream sections of the Yangtze River,including both the mainstem and its tributaries.

The design of fish passage facilities in hydropower projects primarily relies on the swimming ability parame-ters of target fish species.This study investigated interspecific differences in the individual swimming capacities of juvenile fish from five Schizothorax species in the Yarlung Zangbo River basin,aiming to provide a scientific basis for fishway design and ecological conservation.The subjects comprised juveniles of five species:Schizothorax oconnori,S.macropogon,S.waltoni,Schizopygopsis younghusbandi,and Oxygymnocypris stewartii.The mean body lengths of experimental fish were(9.2±0.8),(3.1±0.1),(8.3±0.8),(5.8±0.9),and(5.4±0.6)cm,respectively.Using an incremental velocity test,the induced flow velocity(Uind),critical swimming speed(Ucrit),and burst swimming speed(Uburst)of the five species were measured.Results revealed that the mean Uaind varied between 2.3 and 6.7 cm/s,while the mean Urind varied between 0.4 and 0.8 BL/s.The mean Uacrit varied between 31.1 and 60.8 cm/s,and the mean Urcrit ranged from 6.3 to 10.4 BL/s.The mean Uaburst varied between 39.7 and 88.1 cm/s,with the mean relative Urburst varied between 9.7 and 14.6 BL/s.One-way ANOVA and bivariate correlation analysis(body length & swimming capacity metrics)demonstrated significant differences were observed in the swimming performance among the five studied Schizotho-racinae fish species at juvenile stages.Schizothorax oconnori and Schizothorax waltoni exhibited higher response flow velocities,whereas Oxygymnocypris stewartii and Schizopygopsis younghusbandi demonstrated advantages in burst swimming speed.This difference is primarily reflected in their adaptation strategies to torrential and slow-flow habitats.Within the body length range studied,body size was found to influence certain performance metrics.The results provide crucial data support for understanding the swimming capabilities of Schizothoracine fish and for the design effective fishways in the Yarlung Zangbo River basin,revealing interspecific differences in individual swimming performance and offering to scientifically informed ecological conservation.

To investigate the role of carbon(δ13C)and oxygen(δ18O)stable isotopes in juvenile otoliths for identifying chum salmon(Oncorhynchus keta)groups,this study analyzed cultured and wild juvenile chum salmon groups(under 1 year old)using stable isotope mass spectrometry.The results showed that the mean δ18O and δ13C values in otoliths of the cultured group were(−10.33±0.30)‰ and(−8.60±0.45)‰,while those of the wild group were(−9.90±0.34)‰ and(−11.76±0.65)‰,respectively.Significant differences in otolith stable isotopes were observed between the two groups,primarily attributed to distinct freshwater habitat conditions experienced during their early life stages.By analyzing the correlation between δ18O and δ13C in juvenile chum salmon otoliths,cultured and wild juveniles were successfully discriminated,demonstrating the feasibility of juvenile otolith isotopes for tracing the origin of migratory adult chum salmon.This approach also provides a scientific basis for evaluating the effectiveness of artificial stock enhancement and its ecological impact on wild groups.

This study aimed to investigate the effects of dietary vitamin A and determine its requirement of juvenile red swamp crayfish(Procambarus clarkii).Six isonitrogenous,isolipidic,and isoenergetic experimental diets were formu-lated with analyzed vitamin A potencies of 11573(A1),20042(A2),26274(A3),37818(A4),55159(A5),and 79200(A6)IU/kg,respectively.These diets were fed to crayfish with an initial average body weight of(3.40±0.01)g for 8 weeks.The results revealed that weight gain rate and specific growth rate were significantly higher in groups A4 and A5 compared to the control group(A1)(P＜0.05),with the highest values observed in group A4.In contrast,feed conversion ratio and hepatosomatic index were significantly decreased(P＜0.05),reaching the lowest values in group A4.Compared to the control group,the total antioxidant capacity,catalase,and superoxide dismutase activities in the hepatopancreas were significantly enhanced(P＜0.05)in group A4.Serum aspartate aminotransferase and alanine aminotransferase activities decreased initially and then increased with rising vitamin A levels,both attaining their mini-mum in group A4.Simultaneously,the incidence of B-cells and R-cells in the hepatopancreas,intestinal villi length and width,and activities of hepatopancreatic trypsin,amylase,lipase,and intestinal trypsin were significantly elevated in group A4(P＜0.05).Furthermore,group A4 significantly up-regulated the gene expression levels of Chitinase,EcR,and RXR in the hepatopancreas,while significantly down-regulating the expression of MIH(P＜0.05).In conclusion,opti-mal vitamin A supplementation improve digestive function,enhance hepatopancreas antioxidant and immune capacity,and regulate ecdysis-related gene expression,thereby promoting growth performance in P.clarkii.Based on broken-line regression analysis of weight gain rate,specific growth rate,and feed conversion ratio,the recommended dietary vitamin A requirement for juvenile Procambarus clarkii is 37976-43443 IU/kg.