This study aimed to understand the gonadal development and reproductive characteristics of the black scraper (T.modestus) before and after spawning.From November 2021 to March 2022,the parent fish were collected for five times,with three males and three females at each time.The total length,body weight,hepatopancreas index and gonadosomatic index were measured every time.At the same time,paraffin-embedded sections and hematoxylin-eosin staining were used to observe the gonadal development.The results showed that under artificial temperature control,the gonad weight and gonadosomatic index of the female and male parental T.modestus reached the maximum in February,and entered the peak period of sexual maturity,which was significantly higher than that in other months (P<0.05),suggesting that the parent fish reached the peak of maturity in February under the condition of artificially controlled water temperature.The spawning type of T.modestus was asynchronous and batch spawning,and the ovarian development of T.modestus could be divided into six phases,which was peri-nucleolus,yolk vesicle,primary yolk,secondary yolk,teritary yolk,and ripe stage,respectively.The testis development of T.odestus could be divided into five phases,which was spermatogonium,primary spermatocyte,secondary spermatocyte,spermatid and spermatozoa,respectively.In conclusion,this study investigated the morphological characteristics,organizational structure and developmental rules at different gonadal development stages of T.modestus,which may enrich the basic data of reproductive biology and provide scientific basis for artificial breeding and seed production of T.modestus.

Culter alburnus has high nutritional, economic and ecological values, but its wild resources tend to be exhausted in recent years. So, it is urgent to protect germplasm resources of C.alburnus. In this study, the molecular marker of mtDNA Cyt b gene was used to investigate the genetic diversity and genetic structure of C.alburnus populations in Tai Lake and Hongze Lake, and the Cyt b gene sequences were amplified and sequenced. The research results showed that the full length of Cyt b gene was 1 141 bp, and the base content of A+T was higher than that of G+C.29 variable sites were detected and 29 haplotypes were defined in 98 Cyt b sequences. The average haplotype diversity (Hd) and nucleotide diversity (Pi) of C.alburnus were 0.923 and 0.002 74, respectively, and the average number of nucleotide differences was 3.127. The Hd values of Tai Lake and Hongze Lake populations were 0.927 and 0.816, respectively, and the Pi values of two lake populations were 0.002 85 and 0.002 20, respectively. The genetic diversity of C.alburnus showed high Hd and low Pi. The results of molecular variance analysis showed that the proportion of molecular variation within populations was 15.01%, and the proportion of molecular variation between populations was 84.99%. The coefficient of genetic differentiation (Fst) was 0.150 15 (P<0.01), indicating that there was significant genetic differentiation between the two populations. The values of Tajima's D and Fu's Fs neutral tests were both negative, but significant difference was only found for Fu's Fs neutral test. Furthermore, the mismatch distribution curve was obvious unimodal. Both neutral test and mismatch distribution suggested C.alburnus had experienced population expansion in evolutionary history. In a word, the present results could provide scientific data for the management and protection of C.alburnus germplasm resources in Tai Lake and Hongze Lake.

In order to explore the best method of heterologous migration of Leuciscus merzbacheri,and actively carry out the protection of germplasm resources,cage net,river net and purse seine were used to collect fish and put them into three kinds of temporary ponds:micro-soil pond,cement pond and net cage in the present study.The seeds were transported to the Aquatic Wildlife Rescue Center of Xinjiang for a long distance using canvas water tanks,iron water tanks and fish fry bags,and were treated with sodium chloride,povidone iodine and potassium permanganate for domestication.The results showed that the survival rate of purse seine fishing was the highest(97.47%),that of cage culture was the best(92.86%),that of transportation of fish fry bag with oxygen and cooling was the highest(97.17%).Using 15-20 mg/L potassium permanganate solution and medicated bath for 20-30 minutes,the effect of sterilization and wound healing could be improved,and the number of survivors could be ensured.A total of 534 original species were collected in three years,195 were domesticated and preserved,and the final survival rate was 36.52%.The successful relocation laid a good foundation for the future large-scale propagation of seedlings.

With the gradual rise of aquaculture of Mastacemblus armatus,the problems such as germ plasm confusion and unclear genetic background have become increasingly prominent,which are not conducive to the commercial development of variety.In order to explore the breeding potential of M.armatus,this study used wild M.armatus as parents to construct 17 full-sib families through full-sib breeding model.After 18 months of cultivation,seven effective families were finally obtained.The single trait animal model was used to estimate the breeding value and heritability of each individual by BLUP,with the average body weight of each family as a covariate.The variance component evaluation results of the full-sib family weight of 18 pfm M.armatus showed that the heritability was(0.468 1±0.173 7),the t test reached P<0.01,and the body weight had a positive correlation with breeding value.The regression equation of male was y=0.393 6x-84.193 0(R²=0.755 4,P<0.01);the female was y=0.517x-64.126(R²=0.817 8,P<0.01).The females with the top 50 breeding values were mainly concentrated in family B,E and D,especially family B,the top 24 females and top 19 males were from this family.The maximum breeding value of male fish was 75.09,and that of female fish was 67.49,both of them were from the same family B.Through this study,the M.armatus had high heritability of body weight,which could be selected by phenotype or BLUP breeding value.