Initial Post-Release Performance of Cultured Cyprinus chilia Juveniles in a Shallow Lake in Southwestern China.

The post-release performance of cultured fish is crucial for understanding the viability of cultured fish and assessing the effects of stock enhancement programs. This study aimed to investigate the initial post-release performance of cultured Cyprinus chilia juveniles by examining their movement, spatial distribution, gut fullness, and gut microbiota in nature. In July 2022, a total of 20,000 C. chilia juveniles, tagged with visible implant fluorescence (VIE), were released into Qilu Lake, a shallow lake in southwestern China. Subsequently, continuous recapture was conducted at fixed recapture sites using trap nets during the first 7 days, one month and three months after release. Out of the released fish, 512 were recaptured, resulting in a recapture rate of 2.56%. The recaptured fish had a 100% tag retention rate. The majority (98.05%) of the recaptured fish were found in the recapture sites located on the eastern or western lakeshore, while only 10 fish were recaptured from the recapture sites in the northern lake area. The water depth range where the recaptured fish were found ranged from 190 to 350 cm, with most fish preferring depths less than 300 cm. The majority of the released fish migrated towards the eastern and western lakeshore, with long-distance movement (greater than 100 m) primarily occurring within the first four days after release. The level of gut fullness in the released fish initially decreased and then increased over time following release. Regarding gut microbiota, the dominant phyla observed in most samples were Firmicutes, Proteobacteria, Cyanobacteria, and Fusobacteria. Furthermore, significant variations in the dominant genera were observed across different samples. Principal coordinates analysis (PCoA) revealed clear separation between the microbial communities of pre-release and post-release C. chilia juveniles. This study demonstrated that VIE tagging was a suitable method for short-term marking of C. chilia juveniles. Lakeshores with water depths less than 300 cm were identified as preferred habitats for C. chilia juveniles. The primary adaptation period for cultured C. chilia juveniles released into the natural environment was found to be approximately 4-5 days. These findings contribute to our understanding of the post-release performance of cultured fish and may provide guidance for the management and evaluation of relevant stock enhancement programs.

Effects of neuropeptide Y as a feed additive on stimulating the growth of tilapia (Oreochromis niloticus) fed low fish meal diets.

Neuropeptide Y is known to stimulate food intake in fish. In this study, we investigated tilapia NPY (tNPY) both for its effects on the growth of tilapia (Oreochromis niloticus, GIFT) in low fish meal and for its thermal stability. Three diets were formulated containing 0, 3 and 10 % fish meal (NF, LF and HF). From these diets, six experimental diets were prepared by spraying either tNPY solution (0.3 µg/g feed) or distilled water (DW) onto the surface of formulated feeds (NF + DW, NF + tNPY, LF + DW, LF + tNPY, HF + DW and HF + tNPY). Tilapia were fed the six experimental diets for 8 weeks. Fish in the NF + tNPY, LF + tNPY and HF + tNPY groups showed increasing trends in the weight gain rate and specific growth rate compared to its corresponding control group. The feed coefficient of group HF + tNPY was significantly lower than that of the control group. The growth performance of the LF + tNPY approached that of the HF + DW group. The mRNA levels of npy in NF + tNPY were significantly higher than those in NF + DW. A field experiment in which tNPY was sprayed in feeds by the vacuum spray method with doses of 0, 0.2 and 0.4 µg/g feed was performed for three months, and the FBW of tilapia receiving tNPY at 0.2 and 0.4 µg/g feed was higher than that of the control group although not significantly. The bioactivity of tNPY was confirmed by its ability to reduce cAMP levels and activate the ERK1/2 pathway. These results demonstrated that tNPY could promote tilapia growth with oral administration low fish meal diets.

The complete mitochondrial genome of Sinocyclocheilus aluensis (Cyprinoidea: Cyprinidae).

We describe the complete mitochondrial genome of the endangered fish Sinocyclocheilus aluensis. It is a circular molecule of 16,583 bp in size with a D-loop region and contains 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes and 13 protein-coding genes, and all genes show the typical gene arrangement conforming to the vertebrate consensus. The overall base composition of S. aluensis mitogenome is 31.1% for A, 26.9% for C, 16.6% for G, and 25.4% for T. The percentage of G + C content is 43.5%. Phylogenetic analysis demonstrated that all Sinocyclocheilus species clustered together and formed a monophyletic group. The mitochondrial genome sequencing for S. aluensis in this study provides important molecular data for further evolutionary research for Sinocyclocheilus.

The complete mitochondrial genome of Pareuchiloglanis myzostoma (Teleostei, Siluriformes).

Pareuchiloglanis myzostoma is a key-listed protected indigenous fish species in Nujiang, Yunnan, China. In this study, we firstly reported the complete mitochondrial genome of P. myzostoma, which was 16,584 bp in length, containing 13 protein-coding genes, 22 transfer RNAs (tRNAs), 2 ribosomal RNA genes (rRNAs), and a non-coding control region (D-loop). The overall base composition of P. myzostoma was 30.7% for A, 24.2% for T, 16.0% for G, and 29.1% for C. Phylogenetic analysis showed that all Sisoridae species clustered together formed a monophyletic group. This work would provide a set of useful data on further molecular evolution studies of this precious species.