The authentication of high-quality fishery products originating from specific geographical regions is urgently needed worldwide. Chinese mitten crabs (Eriocheir sinensis), originating from Yangcheng Lake, are prime counterfeiting targets for the same reasons. Foreign crabs that are cultured briefly in the lake, known as “bathed” crabs, are illegally marketed as natives, negatively impacting the product quality. To establish a method for distinguishing “bathed” and genuine crabs, in this paper we conduct a comparative investigation by an Agilent 7500ce ICP-MS on multi-mineral element profiling of the third pereiopod from genuine and one month deliberately “bathing” cultured crabs. The profiles of 11 elements were significantly different between the genuine and foreign crabs before and after bathing. The discriminant analysis reached 100% accuracy to separate the genuine and “bathed” crabs into different groups. Bathing culture was unable to converge element profiles between the genuine and foreign crabs. The biogeochemical profiles can be effective for distinguishing “bathed” crabs.

The estuarine tapertail anchovy, Coilia nasus, is a migratory fish with high economic value in China. We collected fish from the Changjiang River (the Yangtze River) estuary, the Qiantang River estuary, and the southern Yellow Sea, and studied their relationships using otolith elemental and stable isotopic microchemistry signatures to assess the population connectivity of C. nasus. Results show that, in addition to Ca, other elements were present in the otolith core. The δ¹⁸O, Na/Ca, Fe/Ca, and Cu/Ca values of the Qiantang population were significantly higher than those of the others, whereas its δ¹³C and Ba/Ca values were found to be significantly lower. Otolith multi-element composition and stable isotope ratios differed significantly between the Qiantang and Changjiang estuary groups (p < 0.05); however, no difference was observed between the latter and the Yellow Sea group. Cluster analysis, linear discriminant analysis, and a self-organizing map strongly suggest possible connectivity between the fish populations of the Changjiang estuary and Yellow Sea, while the population of the Qiantang River estuary appears to be independent. Notably, results suggest a much closer connectivity between the fish populations of the Changjiang River and the Yellow Sea.

Copper (Cu) contamination has become a severe problem in freshwater environments worldwide. The freshwater mussel Anodonta woodiana is used as a unique bioindicator to monitor Cu contamination in freshwater environments. However, Cu toxicity and response mechanisms in A. woodiana are still largely unknown. A sublethal acute exposure experiment (2.0 mg/L Cu exposure for 72 h) was conducted to investigate the effects of Cu bioaccumulation on ionoregulatory homeostasis, histological features, and transcriptome responses using A. woodiana gills as indicator tissue. The gill bioaccumulation capacity was up to 474. Cu bioaccumulation decreased Na⁺ and Mg²⁺ concentrations (p < 0.05) by 82% and 17%, respectively, and induced cilia loss, epithelial desquamation, and filament atrophy of the gills. Transcriptome analysis identified 3160 differentially expressed genes (DEGs), including 1870 upregulated and 1290 downregulated genes. GO enrichment analysis showed that cellular processes, metabolic processes, biological regulation, and responses to stimuli contained the most DEGs in the biological processes. KEGG pathway analysis showed that apoptosis, arginine and proline metabolism, the toll-like receptor signaling pathway, apoptosis-multiple species, histidine metabolism, beta-alanine metabolism, cytokine–cytokine receptor interaction, and the p53 signaling pathway were significantly enriched. These findings provide comprehensive evidence for exploring Cu toxicity and response mechanisms in freshwater mussels.

To confirm whether Chinese mitten crabs (Eriocheir sinensis), commonly known as hairy crabs or river crabs, in non-Yangcheng Lake areas undergo morphological convergence with the original crabs in the Yangcheng Lake purse seine and high-standard modified aquaculture ponds after being “introduced” or “bathed”-cultured, we employed a geometric morphometrics approach. This approach allowed us to compare and analyze the dynamic changes in the carapace morphology of both the original and “introduced” crabs in Yangcheng Lake and high-standard ponds in Kunshan City at 0, 7, 14, and 30 days after “bathing” culture. The geometric morphological analysis of the carapace was conducted using a system of 35 established landmarks. The stepwise discriminant analysis of the relative distortion score revealed morphological differences between “introduced” and resident original crabs in the Yangcheng Lake area and in high-standard modified ponds after 7, 14, and 30 days of bathing culture. The accuracy of the discriminant analysis was 100%. The results of the geometric morphological visualization demonstrated that the carapaces of the bathed crabs underwent adaptive changes in the water. However, even after one month of bathing culture, the “introduced” crabs in lakes and ponds could not reach the morphological characteristics of the original crabs, i.e., their carapaces did not exhibit the characteristics of the original crabs.

The estuarine tapertail anchovy Coilia nasus is distributed throughout the Dayang River. However, the life history and habitat use of this fish remain unknown. Here, the microchemistry patterns of Sr and Ca in 23 otoliths collected from the lower reaches of the Dayang River were analyzed using an X-ray electron probe microanalyzer. The anchovies were divided into two patterns: (1) with low Sr/Ca ratios (3.0) phases and Sr concentration maps showing various colors, including blue, green, yellow, and red, from the core to the edge of otoliths, whose larvae hatched in freshwater and spent their first winter in brackish or sea waters. The juveniles then stayed in estuarine water areas for further growth and feeding until sexual maturity, when the mature adults returned to the spawning grounds in the river. The co-existence of freshwater residents and anadromous C. nasus in the Dayang River has been studied for the first time, and its possible spawning ground was discovered. These findings provide essential information to effectively protect this species and guide its rational, sustainable utilization.