In 2017,the Chishui River basin became the first to enforce the complete fishing ban,serving as a pilot demonstration area for the subsequent ten-year fishing ban on the Yangtze River.Research on fish growth and repro-ductive traits after the fishing ban provides a scientific basis for evaluating the fishing ban efficacy and guiding popula-tion conservation.This study examined the growth and reproductive characteristics of Acrossocheilus monticola,an endemic species of the upper Yangtze River,in the Chishui River from March 2023 to June 2025.We compared our results with those of the pre-fishing ban(2014-2017)to examine how the fishing ban affected fish growthand repro-ductive traits.A total of 426 A.monticola specimens were collected,with 419 aged.The female-to-male ratio was 1﹕0.52.The length-weight relationships for female and male fish were W♀=2.219×10–5L3.001 and W♂=2.008×10–5L3.019,respectively,indicating isometric growth.Specimens ranged in age from 1 to 6 years.Maximum longevity was 6 years for females and 4 years for males.The asymptotic length and weight for females were 282.6 mm and 503.9 g,with k=0.129 and theoretical age at zero length(t0)=–2.476.For males,the asymptotic length and weight were 255.0 mm and 369.9 g,with k=0.160 and theoretical age at zero length(t0)=–1.946.A.monticola appears to be a batch spawner,with a mean absolute fecundity of(3092±1223)eggs.Mean relative fecundity was(21.2±8.4)eggs/mm and(46.8±18.9)eggs/g relative to body length and body weight,respectively.Relative to the pre-fish ban period,the dominant length class shifted from 100-120 mm to 120-160 mm,and the dominant weight class from 0-40 g to 20-80 g.Maximum observed age increased from 4 to 6 years,while absolute fecundity rose by 71.9%.These findings indicate that the fishing ban has contributed to improvements in the growth and reproduction and population structure of A.monticola in the Chishui River.To promote fish resource conservation in the Chishui River,We suggested continuing the complete fishing ban after the 10-year moratorium expires.Concurrently,habitat protection and restoration should be strengthened,and long-term monitoring should be conducted on fish biology,population dynamics,and habitat conditions.
To evaluate the effectiveness of the fishing ban in the Anqing section of the Yangtze River,seasonal surveys of fish resources were conducted before and after the ban using a combination of hydroacoustic and net sampling me-thods.The results indicated that:(1)A total of 56 fish species were recorded,with an increase in species number,larger body size of dominant species,and higher diversity after the ban.(2)Fish density increased overall after the ban,being higher in all seasons compared to pre-ban levels,though the difference in summer was not significant(P>0.05).While all habitats experienced density increases,the most pronounced rise occurred in winter,reaching 2.2 to 4.1 times pre-ban levels.(3)The mean target strength increased after the ban,with a significant difference in spring(P<0.05);the proportion of high target strength range increased in autumn and winter.The mean total length of catches increased after the ban,with a significant difference in autumn(P<0.05),and the interquartile range of total length showed an expanding trend,indicating an increase in fish individual size.(4)After the ban,fish density and diversity followed a pattern of A>B>D>C,with significant resource increases observed in historically fished areas,such as the tail of Qingjie island and the estuary of the Wan River.The improvements in fish diversity,richness,and individual size demonstrate that the fishing ban in the Anqing section of the Yangtze River has achieved preliminary ecological effects.However,as the system is in a rapid recovery phase,continued long-term monitoring is essential.Furthermore,the spatial heterogeneity in fish richness and diversity suggests that differentiated management measures should be imple-mented for different habitats:priority protection should be given to the Qingjie island area and the estuary of the Wan River and their natural shorelines,ecological restoration should be implemented for urbanized shorelines,and histori-cally fished areas should be placed under strict control.
This study combined quantitative morphological and molecular methods to investigate intraspecific differen-tiation of Trichodina hypsilepis Wellborn,1967 collected from six geographic regions(Chongqing,Sichuan,Guangxi,Hubei,Guizhou,and Guangdong)and five host species(Lateolabrax japonicus,Misgurnus anguillicaudatus,Paramis-gurnus dabryanus,Hypophthalmichthys molitrix,and Danio rerio)in China.Multi-dimensional quantitative morpho-logical comparisons revealed the following:(1)Analysis based on geographic region_host combination showed that the GX_LJ population exhibited significantly higher values than other populations in most core morphological indices(P<0.001),while the HB_DR population showed significantly lower values(P<0.001),representing the two morpho-logical extremes.The CQ_LJ population was generally lower than the GX_LJ population,but remained significantly larger than the intermediate groups(P<0.05).No significant differences were found among MA populations from different regions,the GZ_HM,or the SC_PD population(P>0.05).(2)By geographic region,the GX and HB popula-tions were identified as the morphologically largest and smallest groups,respectively,while the CQ,GZ,SC,and GD populations were intermediate.(3)By host species,the LJ and DR populations represented the morphologically largest and smallest groups,respectively,with the HM,MA,and PD populations being intermediate.The results of principal component analysis(PCA)from three different dimensions were generally consistent:most populations of T.hypsilepis overlapped with each other,while a few showed a separate distribution,indicating varying degrees of intraspecific morphological differentiation among populations of this species.Further main effect analysis showed that the host factor had a stronger main effect on the morphological differentiation of the adhesive disc than the geographical factor,but the two factors tended to act synergistically.Consistent with molecular findings,varying degrees of genetic diffe-rentiation have occurred among populations of T.hypsilepis.The HB_DR population represents an early diverging group within this species,exhibiting notable morphological and genetic differentiation,yet it has not reached the level of independent speciation.For populations derived from loaches(MA and PD population)that have not shown obvious morphological differentiation,varying degrees of genetic differentiation have already occurred at the genetic level.In summary,based on the morphological,molecular,and host evidence,the present study has validated the species vali-dity of T.hypsilepis,a taxon that has been controversial in taxonomic history.
Stocking density is a key factor affecting the growth,health,and rearing environment of farmed fish.As a functional feed additive,fructooligosaccharides(FOS)can effectively alleviate rearing stress,promote growth,and enhance antioxidant capacity.To investigate the effects of different stocking densities and FOS supplementation on the growth performance,antioxidant capacity,and intestinal microbiota of mandarin fish(Siniperca chuatsi),an 8-week indoor recirculating aquaculture experiment was conducted.Mandarin fish with an initial body weight of(29.19±0.47)g were allocated into five groups:low density(LD,1 kg/m3),medium density(MD,3 kg/m3),high density(HD,5 kg/m3),high density with 1%FOS(HF1,5 kg/m3+1%FOS),and high density with 2%FOS(HF2,5 kg/m3+2%FOS).The results showed that the survival rate(SR),weight gain rate(WGR),specific growth rate(SGR),and feed efficiency(FE)of the LD and HD groups were significantly lower than those of the MD group(P<0.05),indicating that both low and high densities inhibited growth performance and feed utilization.Compared with the MD group,the activities of superoxide dismutase(SOD),catalase(CAT),and glutathione peroxidase(GSH-PX)in the liver of the LD and HD groups were significantly increased(P<0.05),suggesting that the fish maintained homeostasis by enhancing antioxi-dant capacity.Regarding the intestinal microbiota,Fusobacteriota was the dominant phylum in all density groups,but the abundances of Proteobacteria,Firmicutes,and Actinobacteriota in the LD and HD groups were significantly increased,indicating a trend toward diversification of the microbial community.Compared with the HD group,both HF1 and HF2 groups showed increases in WGR,SGR,FE,and condition factor(CF),with significant differences observed in the HF2 group(P<0.05),indicating that 2%FOS supplementation significantly improved growth perfor-mance,feed utilization,and condition factor.Moreover,the HF2 group exhibited significantly increased hepatic SOD and CAT activities,demonstrating that FOS supplementation enhanced antioxidant capacity.In addition,the 2%FOS group showed significantly increased alpha diversity of the intestinal microbiota,and PCoA revealed a distinct separa-tion of the microbial community structure,with a significantly increased proportion of beneficial bacteria(e.g.,Bacil-lus),indicating a significant shift in the microbial structure(P<0.05).In conclusion,both high and low stocking densi-ties significantly reduced growth performance and feed utilization of mandarin fish,and the fish maintained homeosta-sis under density stress by enhancing antioxidant capacity.Dietary supplementation with 2%FOS effectively alleviated high-density stress,improving growth performance,feed utilization,antioxidant capacity,and intestinal microbiota diversity in Siniperca chuatsi.These findings provide a theoretical basis for the healthy aquaculture and nutritional regulation of mandarin fish under high-density conditions.
This study aimed to investigate the effects of dietary supplementation with fermented Aurantii fructus immaturus residue(FAFI)on growth performance,antioxidant capacity,liver health,immune response,and gut micro-biota in bullfrogs(Lithobates catesbeianus).A total of 480 healthy L.catesbeianus with an initial body weight of(9.60±0.10)g were randomly allocated into two groups:a control group(CON)fed a basal diet,and an experimental group(5%FAFI)fed the basal diet supplemented with 5%FAFI for 56d.Compared to the CON group,the 5%FAFI group showed significantly improved final body weight and weight gain rate(P<0.05).Digestive enzyme activities and intestinal morphology were also enhanced(P<0.05).Serum activities of ALT and AST,and the contents of TC and TG were significantly decreased(P<0.05),while AKP and ACP activities were markedly increased(P<0.05).Hepatic antioxidant assessment revealed significantly elevated activities of SOD,CAT,GSH,and up-regulated expression of related genes(sod,cat,gsh-px,gstp)(P<0.05),alongside a reduction in MDA content(P<0.05).Intestinal gene expres-sion analysis indicated suppressed pro-inflammatory cytokines(tnf-α,il-1β)and significantly elevated anti-inflamma-tory cytokine(il-10)(P<0.05).The Richness index and Chao1 index of the intestinal microbiota in the 5%FAFI group were significantly lower than those in the CON group(P<0.05).At the phylum level,the abundance of Firmicutes(76.14%)and Proteobacteria(23.10%)in the 5%FAFI group was slightly higher than that in the CON group(75.59%,20.87%).At the genus level,the relative abundance of Lactococcus was significantly increased(P<0.05),while multi-ple potentially pathogenic bacterial genera,such as Citrobacter and Edwardsiella,showed a decreasing trend.In conclusion,dietary supplementation with 5%fermented Aurantii fructus immaturus residue can effectively enhance growth performance and overall health in bullfrogs by improving antioxidant capacity,modulating liver metabolism,regulating immune responses,and optimizing the structure of the intestinal microbiota.
