In this study, the effect of solid-state fermentation with Bacillus subtilis GYB6, Saccharomyces cerevisiae NJ1, and Bacillus amyloliquefaciens Y8 on the anti-nutritional factors, nutritional components, bioactive compounds, antioxidant activity, functional properties, and structure of rapeseed meal (RSM) were investigated. Results showed that the action of three strains in the fermentation of RSM caused a significant decline in glucosinolates, phytic acid, crude fiber, and tannins by 99.18%, 42.41%, 27.21%, and 34.17%, respectively. The amount of crude protein, amino acids, and peptides of RSM increased significantly after fermentation. The SDS-PAGE results showed that 12S globulin and 2S albumin protein were almost entirely degraded. Fermentation considerably increased the concentration of total phenolics and flavonoids, and activated antioxidant activity and functional properties. Furthermore, the structural variation was observed by scanning electron microscopy and FTIR spectroscopy. Thus, these results indicated that the solid-state fermentation process in this study was a promising approach to enhance both the nutritional value and bioactivity of RSM, which could be used as value-added functional animal food ingredients.

Off-seasonal water level regulations disrupt the biological traits and phenological rhythms of native fish species, yet their impacts on interspecific trophic interactions remain understudied. This study employed stable isotope analysis to assess the trophic dynamics of three fish species (Parabramis pekinensis, Carassius auratus, and Toxabramis swinhonis) across different water periods in Hongze Lake. The findings revealed that all three species occupied similar mid-level trophic positions, with no significant difference among water periods (p > 0.05). During high-water periods, P. pekinensis and T. swinhonis exploited broader niches, while C. auratus relied on a narrower diet. In contrast, during low-water periods, C. auratus expanded its niche, while P. pekinensis and T. swinhonis reduced their isotopic niche widths. Niche overlap analysis showed minimal trophic overlap among the three species during high-water periods, with increased overlap during low-water periods, except for the highest overlap between C. auratus and T. swinhonis during mid-water periods. This variation in niche overlap aligns with shifts in dietary reliance, as POM was the predominant dietary component for all three species, but its contribution varied significantly across different water periods. These findings indicated that adaptive trophic niche facilitated the coexistence of these fish species, while off-seasonal water level regulation may intensify interspecific competition. These insights are essential for refining water management policies and developing sustainable fishery management strategies of Hongze Lake and other water-level-regulated systems.

Investigating fish diversity in canyon rivers through conventional fish surveys is challenging due to precipitous conditions, including steep slopes, rapid water flow, and complex habitats. Additionally, intensive construction of dams has further complicated the understanding of contemporary fish diversity in these rivers. In this study, we used the environmental DNA (eDNA) technique to assess fish diversity and examine the effects of dams on fish diversity in the Mabiehe River, a canyon river in the upper reaches of the Pearl River drainage. Water samples from 15 sampling sites were collected, yielding 9,356,148 valid sequences. Utilizing the NCBI public database, a total of 60 freshwater fish species were identified, with Carassius auratus, Cyprinus carpio, and Pelteobagrus fulvidraco being the most dominant species in the Mabiehe River. We also detected one nationally protected fish species, three provincially protected fish species, and six exotic species in this river. Furthermore, eDNA analyses demonstrated that the lotic river sections harbor more species and greater diversity than dammed sections, suggesting that dams might exert significant impacts on local fish diversity. Overall, this study supports the effectiveness of the eDNA technique as a complementary tool to traditional field surveys for monitoring fish biodiversity in canyon rivers.