Abstract:Growth traits in largemouth bass (Micropterus salmoides) are crucial indicators of quality and yield. Thedevelopment of growth single nucleotide polymorphism (SNP) markers and exploration of dominant genotypesand growth genes will enhance our understanding of the genetic mechanisms underlying growth and development.Moreover, this research will facilitate the selection and breeding of new populations with exceptional growth traits.Using restriction site-associated DNA sequencing (RAD-seq), we conducted SNP screening in the F0 generation ofthe northern subspecies of largemouth bass, focusing on extreme groups with very high body weights (top 1%) andvery low body weights (bottom 1%). A general linear model (GLM) was applied to establish correlations betweenthe SNP genotypes and four growth traits (body weight, body length, body height, and body thickness) in a cohortof 230 F0 individuals. Additionally, candidate genes associated with growth were predicted using gene annotationinformation, and the combined additive effects of the dominant genotypes were analyzed through examination oftheir aggregation. A total of 4196486 high-quality SNPs were identified across 23 chromosomes of the largemouthbass. Using a population-specific genotype frequency threshold of 0.7, we initially screened 100 potential SNPloci related to growth and identified 12 that were significantly associated with growth. Specifically, five SNPswere significantly associated with body weight, 10 SNPs were significantly associated with body length, fourSNPs were significantly associated with body height, and five SNPs were significantly associated with bodythickness. Notably, the candidate growth genes fam174b, diaph2, kiaa1549lb, and ppip5k1b were linked to specificSNP markers including SNP19140160, SNP24406191, SNP3355498, and SNP9244620, respectively. Theenrichment of 6−10 dominant genotypes resulted in an average increase of 32.07% in body weight, 9.63% in bodylength, 9.96% in body height, and 10.58% in body thickness compared to the enrichment of 0–5 dominant genotypes,significantly improving the effect of genotype enrichment. The 12 fast-growth SNP markers and four candidategrowth genes identified in this study could assist in the improvement of growth traits in largemouth bass.

Abstract:To explore the sperm morphology and physiological characteristics of Hapalogenys mucronatus andenhance the fertilization rate of artificial reproduction, sperm structure was observed using scanning electronmicroscopy and transmission electron microscopy under varying gradients of salinity, pH, and temperature. Ouraim was to investigate the relationship between the rapid movement time, life span, and environmental factors ofH. mucronatus sperm. The results showed that the sperm of H. mucronatus consisted of three parts: the head,middle part, and flagella. The head of the sperm was nearly spherical or ellipsoidal, with a diameter of (1.56±0.05)μm. Chromatin in the nucleus was highly concentrated, and the nuclear membrane was close to the plasmamembrane without the acrosome. The middle part was mainly composed of a sleeve cavity and a centriole complex.The flagellum is slender and has lateral fins, which is a typical “9+2” microtubule structure. The suitable salinityrange for Hapalogenys mucronatus sperm was 22–28, and the sperm lifespan reached a maximum value of 425 swhen the salinity was 26. The optimum pH range was 7–10. Sperm motility was the strongest at pH 7, and spermlifespan reached a maximum of 430 s. The suitable temperature range is 18–26 ℃, and the longest sperm life is427 s when the water temperature is 22 ℃. It is suggested that the optimum water environment conditions for thefertilization of eggs and sperm of H. mucronatus are salinity 24–26, temperature 20–22 ℃, and pH 7–8.

Abstract:

Cultivation of pseudofemale largemouth bass (Micropterus salmoides) is a key step in the preparation of

all-male fry. To determine the optimum parameters for the female sex reversal of largemouth bass, establish the

sex induction technique of pseudofemale fish, and prepare all-male fry, juvenile largemouth bass (15 days

post-hatching, 1.00±0.01 cm in length) were fed with artificial compound feed mixed with 17β-estradiol (17β-E₂)

or trilostane (TR). The diets of the three experimental groups contained 30 mg/kg 17β-E₂, 30 mg/kg TR, and 20

mg/kg 17β-E₂+10 mg/kg TR, which were named E30, TR30, and E20TR10, respectively. The feed of the control

group did not contain 17β-E₂ and TR, which was named C. The effects of 17β-E₂ and TR on the growth

performance, female ratio, and gonadal tissue development of largemouth bass were analyzed after a 60-day

feeding period. At the age of 12 months, the blood and gonadal tissues of pseudofemales in each experimental and

control group were collected to detect the concentration of sex steroid hormones, expression levels of cyp19a1a

and dmrt1, and ovarian development morphology. The results showed that the body length and weight of the E30

and E20TR10 groups were significantly lower than those of the C group (P<0.05), whereas the body length and

weight of the TR30 group were higher than those of the control group; however, the difference was not significant

(P>0.05). The proportions of females in the E30, TR30, E20TR10, and C groups were 100.00%, 0, 100.00%, and

53.33%, respectively. Gonadal tissue sections showed a large number of primary oocytes in the ovaries of group C.

Ovarian cavities, oogonia, and oocytes were observed in the E30 and E20TR10 groups. However, males in the

TR30 group showed no sexual reversals. At the age of 12 months, the proportions of females in the E30, TR30,

E20TR10, and C groups were 100%, 0, 100.00%, and 46.67%, respectively. Tissue sections showed no

pseudofemales in the TR30 group. The ovarian development of pseudofemales in the other experimental groups

was at stage II. The concentration of estradiol and expression of cyp19a1a in each experimental group were

significantly lower than those in the control group (P<0.05). In summary, largemouth bass pseudofemales can be

produced using the hormone concentrations utilized in this study. However, during the breeding period, the

estradiol content and expression of cyp19a1a in the pseudofemale did not reach the levels observed in normal

females, leading to ovarian retardation. This study provides foundation data for optimizing largemouth bass

feminization.

Abstract:

To investigate the oxidative stress response of gill tissues and the energy metabolism of the adductor

muscle of Crassostrea angulata under hypoxic stress, six dissolved oxygen concentration gradients (0.5 mg/L,

1.0 mg/L, 1.5 mg/L, 2.0 mg/L, 3.0 mg/L, 4. 0 mg/L) were used to treat C. angulata under hypoxic stress for 96 h.

The total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, catalase (CAT) activity,

malondialdehyde (MDA) content of C. angulata gill tissues, alkaline phosphatase (AKP) activity, lactate

dehydrogenase (LDH) activity, and glycogen content of the adductor muscle were determined using enzyme-linked

immunosorbent technique at the 6th, 12th, 24th, 48th, 72nd, and 96th hour of hypoxic stress. The results showed

that: (1) under low oxygen stress for 6–24 h, T-AOC, SOD activity, and MDA content showed the phenomenon of

first increasing and then decreasing, while CAT activity showed the phenomenon of first decreasing and then

increasing; at 24 h, the MDA content of the whole treatment group and the T-AOC activity and SOD activity of

part of the treatment group were restored to the level of the control group; and under hypoxic stress for 24–96 h,

T-AOC, SOD activity, and MDA content increased, then decreased, and then increased again, and CAT activity of

some treatment groups continued to decrease. T-AOC activity of all treatment groups and MDA content and CAT

activity of some treatment groups recovered to the level of the control group at 96 h, except for the 1.0 mg/L

concentration group, which did not have any significant difference from the control group. The SOD activity of the

rest of the treatment groups was significantly lower than that of the control group (P<0.05). (2) Over the 96 h of

hypoxic stress, LDH activity significantly varied among different treatment groups, with a total of three peaks

(P<0.05). AKP activity initially decreased and then increased with stress duration. Glycogen content decreased to

varying degrees with prolonged hypoxic stress time, and after 96 h, the 0.5 mg/L concentration group, showed a

significant decrease in glycogen content (P<0.05), while the other groups showed no significant differences from

the control group. These results suggest that C. angulata exhibits strong hypoxia tolerance by modulating changes

in various enzyme activities within the body to enhance the balance of body's oxidative stress response and energy

metabolism. However, extreme hypoxic environmental stresses still affect the physiological state of C. angulate.

Abstract:

Based on catch survey data from six stations (Gangtuo, Benzilan, Shigu, Panzhihua, Qiaojia, and

Suijiang) in the Jinsha River main stream from May 2022 to November 2023, we analyzed the current status of the

composition of the fish community, characteristics of the dominant species, spatial and temporal distribution of the

diversity of the community, and proposed conservation measures for fish in the Jinsha River main stream. The

study collected a total of 68 fish species, distributed across 4 orders, 15 families, and 48 genera. Cypriniformes

were the most abundant (51 species), accounting for 75.0% of the total species count. Among these, 5 species were

nationally protected fishes, while 7 were exotic. The ecological types of the collected fish mainly included

omnivorous, benthic, and sedentary fishes, representing 66.18%, 44.12%, and 72.06%, respectively. The dominant

species within the community were Hypophthalmichthys molitrix, Coptodon zillii, and Schizothorax dolichonema.

Various diversity indices were calculated: the Shannon-Wiener diversity index (H'), Simpson diversity index (D'),

Peilou evenness index (J'), and Margalef richness index (R'). These indices ranged from 1.376 to 2.012, 0.646 to

0.816, 0.574 to 0.797, and 1.149 to 2.870, respectively. ANOVA analysis revealed the temporal variations in the

four diversity indices were not significant (P>0.05). However, spatial differences were observed to be significant

(P<0.05). ABC curve analysis showed that the biomass curve was above the abundance curve, and the W statistic

value was positive, indicating that the community was less perturbed, but there were some changes in fish species

and ecotypes compared with the historical records. The genera and family diversity indices (G-F) in 2022–2023

decreased from 0.29 to 0.19, but the number of species relatively increased; the results of cluster analysis and

NMDS ordination analysis showed that the fish communities in the mainstem Jinsha River section were divided

into 2 groups: Gangtuo, Benzilan, and Shigu in one group; and Qiaojia, Panzhihua, and Suijiang as the other. The

similarity percentage (SIMPER) analysis showed that the species composition of the fish communities varied

significantly among different seasons, and the main divergent species were Hemiculter tchangi and Rhodeus

sinensis. As a systematic survey conducted after the fishing ban, the present results served as a benchmark for

evaluating the ban’s effectiveness on the Yangtze River. Based on these results, it is recommended to enhance the

management of the fishing ban, monitor the population dynamics of exotic species, and impplement habitat

restoration efforts in both the main stream and tributary streams to safeguard the fish diversity of the Jinsha River.

Abstract:

To assess the germplasm genetic diversity of Zacco platypus populations in the western Wuling

Mountains and Shennongjia Forestry District, we analyzed the genetic diversity and structure of seven Z. platypus

populations using mitochondrial Cyt b sequences and microsatellite DNA (SSR) markers. Our results revealed

144 variant sites and 33 haplotypes among 185 Cyt b sequences from the seven populations. The haplotype

diversity (H_d) ranged from 0.000 to 0.887, and the nucleotide diversity (π) ranged from 0.000 to 0.275. The

neighbor-joining (N_J) phylogenetic tree and median-joining network of Cyt b haplotypes grouped the seven

populations into three branches: Jiangkou1/Jiangkou2 (JK1/JK2), Shennongjia (SNJ), Xishui/Chishui/Wuchuan/

Nanchuan (XS/CS/WC/NC). Analysis of molecular variance (AMOVA) indicated significant genetic differentiation

among the seven populations and among the three branches. Analyses based on 11 microsatellite DNA loci showed

that the mean number of alleles (N_A) in the seven populations of Z. platypus was 3.66, the mean Shannon’s

information index (I) was 0.689, the mean observed heterozygosity (H_O) was 0.315, the mean expected

heterozygosity (H_E) was 0.354, and the mean polymorphic information content (PIC) was 0.409. The genetic

differentiation index (F_ST) among the populations varied from 0.060 to 0.547, with significant genetic

differentiation among the populations (P<0.05). The UPGMA phylogenetic tree and PCoA showed that the seven Z.

platypus populations clustered into four clades. STRUCTURE clustering analysis revealed that the seven

populations of Z. platypus could be classified into four genetic groups. AMOVA showed significant genetic

differentiation among the seven populations and among the four genetic groups of Z. platypus. Hence, the wild Z.

platypus populations in the western Wuling Mountains and Shennongjia Forestry District exhibit low genetic

diversity and significant genetic differentiation. Strengthening the protection of the riverine ecology and

environment is crucial to ensure the sustainable utilization of wild germplasm resources of Z. platypus.

Abstract:To identify the composition and diversity of fish larvae and juveniles in the coastal waters of theMinnan fishing grounds, the species composition and quantity distribution of fish larvae and juveniles, as well asthe relationship between the hydrological characteristics of the waters of the fishing grounds in Minnan and thedistribution of fish larvae and juveniles, were studied. Ecological research data were obtained for the larvae andjuveniles studied in four voyages carried out in May 2022 (spring), November 2022 (autumn), February 2023(winter), and July 2023 (summer). It was found that: (1) a total of 1114 fish larvae and juveniles were collected on4 voyages, belonging to 9 orders, 40 families, and 87 species, of which the number of Perciformes was the largest,accounting for 65.26% of the total number of fish larvae and juveniles in the study area. The abundance of fishlarvae and juveniles and the number of species were the highest in summer, and the abundance of fish larvae andjuveniles and the number of species were the lowest in autumn. The dominant species in each quarter were obvious,and there were no common dominant species. (2) There are significant differences in the composition of the fishlarvae and juvenile clusters in the Minnan fishing grounds. The species replacement rates in the four seasons were88.46%, 98.15%, 100.00%, and 92.11%, respectively. The results of the diversity analysis show that the richnessindex (D) and the Shannon-Wiener diversity index (H') were the highest in the summer, but the Pielou evennessindex (J') was highest in the winter. (3) Analysis of the similarity of the assemblages of fish larvae and juvenilesshowed that the assemblages of fish larvae and juveniles in spring, summer, and winter were obvious. Duringspring, fish larvae and juveniles can be divided into two groups: nearshore and offshore. In summer and winter, thefish larvae and juveniles can be divided into three groups: the nearshore group, the offshore group I, and theoffshore group II. (4) Analysis of the correlation between spatial and temporal distribution and environmentalfactors of the fish larvae and juveniles revealed that the changes in salinity between different stations and thetemperature changes between seasons are the main factors that affect spatial and temporal distribution. The resultsof this study provide a scientific basis for studying the replenishment mechanism of fishery resources in theMinnan fishing grounds and formulating measures for the conservation and management of fishery resources.

Abstract:

With the increasing intensity of human fishing activities and the growing prominence of environmental

pollution issues, the nearshore marine fishery resources in the northern South China Sea have experienced severe

decline. Priacanthus macracanthus has always been one of the main targets of trawl fishing vessels, and it is

facing prominent issues of early maturity and small body size. However, there is a lack of research on the resource

quantity of P. macracanthus. In order to achieve sustainable utilization and management of its resources, it is

necessary to evaluate the maximum sustainable yield (MSY) and catchable resource quantity of P. macracanthus.

The surplus production model is one of the commonly used methods for estimating the biological reference points

of fish stocks. It has the advantages of requiring less data and being easy to operate. However, in the process of

resource assessment, the selection of models and data sources is an important factor that affects the estimation

results of fishery population management parameters, such as optimal fishing effort, MSY, and total allowable

catch (TAC). In order to make the assessment results closer to the real fishery resources, it is necessary to provide

continuous and effective survey data and scientifically reasonable models. Therefore, this study takes the resource

assessment of P. macracanthus in the northern South China Sea as an example. The stratified sampling survey data

of catch production on fishing ports in the northern South China Sea from 2008 to 2020 were used to analyze the

catch per unit effort (CPUE) of each operation gear in different power ranges. Based on six surplus production

models, the MSY of P. macracanthus were estimated. The TAC were estimated according to decision-making

principles and graphical methods. The fishery stock status of P. macracanthus was determined based on the Kobe

diagram. The results showed that the annual trawl catch of P. macracanthus accounted for the highest proportion,

with an average of 79.36%. In the past 10 years, its catch showed a fluctuating downward trend. The Schaefer

model, Fox model, and D-Fox model had good applicability to the CPUE data of P. macracanthus (mean absolute

percentage error MAPE<100%), with estimated MSY ranging (2.5–3.2)×10⁴ t, with an average of 2.9×10⁴ t. The

TAC range was (2.4–3.0)×10⁴ t, with an average of 2.7×10⁴ t. The Kobe diagram showed that the P. macracanthus

stock in the northern South China Sea was in the safety state, and there had been no overfishing in recent years. In

this study, it is discussed that not all the catch data corresponding to the main engine power of fishing vessels can

be analyzed using the surplus production model. Secondly, the catch data corresponding to the same main engine

power range are not applicable to the analysis of all surplus production models. Finally, we believe that when

assessing the MSY of a single fishery resource, it is not only necessary to consider the diversity of assessment

models, but also the use of data from different sources. This study suggests that the different results obtained by

fitting the data from different main engine power ranges of fishing vessels can provide a reference interval for the

values of MSY and TAC. It can also provide a broader perspective on the overall analysis of the assessment results.

Taking the mean value is a beneficial attempt to explore reasonable values for MSY and TAC.

Abstract:

The spatial distribution of species can reflect the interrelationships among individuals, which are the

result of long-term adaptation and selection between species and the environment. This has a significant impact on

the development and resource utilization of species. This study constructed 10 species distribution models based

on the samples collected from the bottom trawl surveys in Haizhou Bay and adjacent waters during springs and

autumns of 2013–2022. We selected models with better performance and prediction accuracy to construct an

ensemble species distribution model (ESDM) based on the true skill statistic and area under the receiver operator

characteristic (ROC) curve. We analyzed the spatial distribution of Chaeturichthys stigmatias and the influencing

factors. The results showed that ESDM could effectively reduce the uncertainty of single-species distribution

models, improve the accuracy of model prediction, and analyze the spatial distribution characteristics of C.stigmatias in Haizhou Bay with higher accuracy. C. stigmatias generally concentrated in the western coastal and

southern waters of Haizhou Bay during the spring seasons of 2013–2022, with lower distribution in the eastern,

central, and northern waters. The longitude and latitude deviation ranges of the distribution center during this

period were approximately 1°. C. stigmatias were mainly distributed in the southwestern area of Haizhou Bay

during autumn, with the distribution center moving slightly. Additionally, we found that water depth, prey density,

sea bottom temperature, and sea bottom salinity were significantly correlated with the spatial distribution of C.stigmatias in Haizhou Bay, of which prey density generated the greatest effect in spring, and water depth generated

the greatest effect in autumn. This study analyzed the spatial distribution characteristics and changes in the

distribution centers of C. stigmatias on a regional scale and explored seasonal differences in important influencing

factors. This study provides basic information for sustainable utilization of C. stigmatias.

Abstract:

Gillnet fisheries targeting grey mullets Mugil cephalus are an important part of small-scale fisheries in

the coastal areas of China. However, in fishery production, the catch efficiency of gray mullet is low and the

number of catches is out of proportion to the fishing effort, which leads to a low economic benefit for the fishery.

Improving the catch efficiency of gray mullets has become an urgent problem that needs to be solved. In recent

years, light-emitting diodes (LEDs) have been widely used to improve the catch efficiency of target species. It

mainly uses the phototaxis of the target species to attract, gather, and trap fish. Many studies have shown that the

gray mullet has phototaxis and may have different phototaxis for different lights. Therefore, the application of

LEDs in gray mullet gillnet fisheries may effectively improve catch efficiency; however, their specific impact

needs to be systematically assessed. In this study, sea trials were conducted in the northern sea area of Rongcheng

from May to June 2023 to test the effects of different LED light colors (red, white, yellow, blue, and green) and

amount (2, 4, 6) on the catch efficiency of gray mullet. A total of 1549 specimens of grey mullet were caught. The

generalized linear mixed effect model (GLMM) was used to evaluate the effect of LEDs on the catch efficiency of

gray mullets. When building the model, CPUE (catch amount per unit of fishing effort) and WPUE (catch weight

per unit of fishing effort) were taken as dependent variables, LED color and quantity as fixed effects, and voyage

time as random effects, according to the Akaike Information Criterion (AIC) and Bayesian Information Criterion

(BIC), to judge the fitting degree of the normal, gamma, Poisson, and negative binomial distributions. The gamma

distribution was selected as the optimal fit to analyze the influence of LED color and quantity influence the catch

efficiency of gray mullets. Compared with LEDs of different light colors, the CPUE of mullet with 2/4/6 green

lights significantly increased by 50.72%, 97.46%, and 98.07%, whereas the WPUE significantly increased by

39.38%, 80.54%, and 84.63%, respectively. The CPUE and WPUE of gray mullets in the test nets with 4 and 6

LEDs were not significantly different (P>0.05). In addition, LEDs improve the catch efficiency of bycatch in sea

bass (Lateolabrax maculatus) and black rockfish (Sebastes schlegelii). Based on the results of this study, green

LEDs are recommended in grey mullet gillnet fisheries to improve the catch efficiency of grey mullet, and the

recommended number is four per net.

Abstract:Litopenaeus vannamei is an important aquaculture species in China, and its production ranks first amongall crustaceans. However, owing to it being a non-native species and its germplasm being limited by its origin inforeign countries, after a period of dividend farming, negative problems such as slow growth, and a low survivalrate, and poor disease resistance have gradually appeared, causing huge losses to shrimp farming. In response tothese problems, researchers in China have actively conducted shrimp breeding and have achieved certain resultsby cultivating several new varieties. In recent years, the development of genetic improvement technology foraquatic animals has been rapid, and the introduction of modern molecular breeding technology has revolutionizedthe breeding of L. vannamei. In this paper, we review the status of molecular breeding technology in L. vannamei,including germplasm resource research, genome research, molecular marker mining and assisted breeding, genomeselection, and gene-editing research. It also provides an outlook on the future development trends of molecularbreeding technology for L. vannamei, with the hope of providing a reference for the breeding of new L. vannamei varieties using these modern molecular breeding techniques.