Sichuan taimen (Hucho bleekeri), a critically endangered species, is listed as a first-class protected species in China. The natural population has been missing from most of its known distribution areas for many years but was rediscovered in the Taibai River in 2012, providing an important resource for the conservation stocking of the Sichuan taimen. In this study, 43 wild adult Sichuan taimen collected from the Taibai River were determined for gamete maturity for artificial reproduction using ultrasonography. The echogenicity of the gonads before and after hormonal induction was described to determine broodstock identification, injection dose of hormones, and spawning time. Four batches of artificial breeding were successfully achieved in 2013, 2014, and 2016. Broodstock (19 females and 16 males) spawned with average fertilization and hatching rates reaching 80.2% and 61.0%, respectively. This study demonstrates that ultrasonic imaging is a convenient and efficient method to track the state of gonads of mature Sichuan taimen during artificial reproduction, which will assist in broodstock cultivation, and further large-scale proliferation and effective resource restoration of the Sichuan taimen.

The Chinese sturgeon (Acipenser sinensis) is an ancient, complex autooctoploid fish species that is currently facing conservation challenges throughout its distribution. To comprehensively characterize the expression profiles of genes and their associated biological functions across different tissues, we performed a transcriptome-scale gene expression analysis, focusing on housekeeping genes (HKGs), tissue-specific genes (TSGs), and co-expressed gene modules in various tissues. We collected eleven tissues to establish a transcriptomic repository, including data from Pacific Biosciences isoform sequencing (PacBio Iso-seq) and RNA sequencing (RNA-seq), and then obtained 25,434 full-length transcripts, with lengths from 307 to 9515 bp and an N50 of 3195 bp. Additionally, 20,887 transcripts were effectively identified and classified as known homologous genes. We also identified 787 HKGs, and the number of TSGs varied from 25 in the liver to 2073 in the brain. TSG functions were mainly enriched in certain signaling pathways involved in specific physiological processes, such as voltage-gated potassium channel activity, nervous system development, glial cell differentiation in the brain, and leukocyte transendothelial migration in the spleen and pronephros. Meanwhile, HKGs were highly enriched in some pathways involved in ribosome biogenesis, proteasome core complex, spliceosome activation, elongation factor activity, and translation initiation factor activity, which have been strongly implicated in fundamental biological tissue functions. We also predicted five modules, with eight hub genes in the brown module, most of which (such as rps3a, rps7, rps23, rpl11, rpl17, rpl27, and rpl28) were linked to ribosome biogenesis. Our results offer insights into ribosomal proteins that are indispensable in ribosome biogenesis and protein synthesis, which are crucial in various cell developmental processes and neural development of Chinese sturgeon. Overall, these findings will not only advance the understanding of fundamental biological functions in Chinese sturgeon but also supply a valuable genetic resource for characterizing this extremely important species.