Due to a sharp decline in resources, Schizothorax waltoni Regan and Percocypris retrodorslis have been listed as wildlife under second-class protection in China. Under culture conditions, the early development and allometric growth patterns of S. waltoni and P. retrodorslis were researched from the hatching stage to 60 DPHs (days post-hatching), and a sampling of ten to fifteen larvae was made every day, followed by measurements with Axio Vision 4.8 software (Carl Zeiss AG, Jena, Germany). Morphological indicators included the anal fin length, the body depth, the body depth at the anus level, the caudal fin length, the dorsal fin length, the eye diameter, the head length, the head depth, the pectoral fin length, the tail length, the trunk length, the snout length, the total length, and the ventral fin length. Based on the morphology development of S. waltoni Regan and P. retrodorslis, four periods of larval growth were identified: pre-flexion larvae at 0–14 DPHs and 0–16 DPHs; flexion larvae at 14–23 DPHs and 16–26 DPHs, post-flexion larvae at 23–50 DPHs and 26–52 DPHs, and the juvenile stage. In newly hatched larvae, most organs and body parts were not differentiated, and they successively developed within 26 DPHs. The depletion of the yolk sac was observed at 23 DPHs and 25 DPHs. Allometric growth mainly occurs in the head and tail regions, indicating that body parts related to feeding and swimming behaviors were more important than the other parts. In addition, the growth pattern shows that the development of organs gives priority to the functions of gill respiration, sensation, exogenous feeding, and swimming. The inflection points of body part growth patterns only appeared before 40 DAH, so future studies should concentrate focus on developing the best feeding from the first feeding to 40 DAH. These outcomes were discussed with regard to the ontogeny of the functional morphology in relation to ecology and aquaculture. It is expected that this research can provide valuable perspectives in species conservation.

This study aimed to determine the practical efficacy of passive eDNA samplers (PEDS) for monitoring fish diversity in riverine ecosystems. It investigated the utility of environmental DNA (eDNA) in accurately depicting fish composition and diversity within the Lancang River. Environmental DNA technology, particularly PEDS, may be used as a substitute for traditional water filtration techniques. However, its effectiveness in natural water ecosystems remains to be proven. The filter materials included mixed cellulose acetate and nitrate (MCE), nylon (NL), glass fiber (GF), and polyvinyl chloride filter membrane (PVC). This study used four different types of filters, each with identical pore sizes and dimensions but constructed from various materials, to assess eDNA capture under laboratory and field conditions in the water samples. The filter materials included mixed cellulose acetate and nitrate (MCE), nylon (NL), glass fiber (GF), and polyvinyl chloride filter membrane (PVC). Environmental DNA macrobarcoding was used to analyze fish biodiversity and to understand the environmental effects on species distribution. Our study identified 50 fish species inhabiting the Lancang River, with equal representation of exotic and native species. A comparative analysis of four filter-based environmental DNA samplers and traditional environmental DNA sampling methods demonstrated comparable species richness. Redundancy analysis indicated that environmental variables, elevation, electrical conductivity, salinity, and chlorophyll-a significantly influenced the distribution patterns of both non-native and native fish species in the river. This study highlights the significance of eDNA technology in evaluating fish diversity across diverse habitats, thereby establishing a theoretical framework for the sustained monitoring and management of fish biodiversity in protected areas.