Teleost otoliths provide a pivotal medium for studying changes in population structure and population dynamics of fish. Understanding the otolith-fish size relationship and intraspecies variation in otolith morphology is essential for the accurate assessment and management of fishery resources. In our study, we aimed to estimate the relationships between otolith morphological measurements and fish length, and detect differences in the otolith morphology of planktivorous and benthivorous morphs of Schizopygopsis thermalis in Lake Amdo Tsonak Co on the Qinghai-Tibet Plateau (QTP). Both morphs exhibited strong linear otolith-fish size relationships; otolith morphology was sexually dimorphic in each morph; the morphs differed significantly in otolith shape and size (e.g., posterior side, the region between the posterior and ventral otolith, otolith length, circularity, and surface density). In addition, we found that the differences in otolith morphology between morphs are related to habitat preferences, diet, and growth. Basic data on the biology of S. thermalis are essential for poorly studied Lake Amdo Tsonak Co, and our study emphasizes that intraspecific variation in otolith morphology should be taken into consideration when differentiating stocks, populations, and age classes based on otolith morphology.

β‐diversity is effective for measuring the degree of compositional variation among communities and can be decomposed into local (LCBD) and species (SCBD) contributions to β‐diversity. Previous studies on β‐diversity have mostly been limited to the taxonomic level; relatively few studies have been conducted on functional diversity and its two components based on species functional traits, which have seriously hindered the potential application of β‐diversity in conservation biology. In addition, increasing anthropogenic disturbance has led to uncertainties in the β‐diversity of fish communities in stream ecosystems. In this study, we explored the relationships between multidimensional β‐diversity of fish communities and regional landscape factors, local environmental factors, community metrics, and species functional traits to reveal the main drivers of β‐diversity in headwater streams of the Xin'an River, China. LCBD and SCBD values were calculated based on species abundance and functional traits, that is, local and species contribution to taxonomic (TLCBD and TSCBD, respectively) and functional (FLCBD and FSCBD, respectively) β‐diversity. The results showed that LCBD and SCBD values were affected by biological and environmental factors. Among biological drivers, TLCBD values were positively related to species abundance. FLCBD values were positively related to species abundance, functional originality, specialization, and dispersion, that is, sampling sites with greater ecological uniqueness at the taxonomic level also had greater ecological uniqueness at the functional level. Among environmental drivers, TLCBD and FLCBD values were negatively related to water temperature, substrate coarseness, and agricultural and urban land use, that is, anthropogenic land use and local environmental changes reduce the ecological uniqueness of fish communities in the studied streams. For SCBD, both TSCBD and FSCBD values were affected by species abundance, occupancy, and niche position. We suggest that consideration of SCBD as part of a conservation approach needs to be coupled with species abundance and occupancy, which will help to prioritize areas for conservation and restoration in the study region.

Dam construction can significantly alter local habitat characteristics and the distribution patterns of aquatic organisms. However, the variations in the multidimensional diversity of fish assemblages in reservoirs, as well as the relative significance of potential community assembly rules, remains poorly understood. This study elucidated the patterns of taxonomic and phylogenetic α- and β-diversity with its decomposition components (i.e., turnover and nestedness) of fish assemblages in the Dongfeng Reservoir, situated in the karst basin of southwest China. Additionally, we evaluated the relative importance of environmental heterogeneity and spatial structure. We found significant nonlinear relationships (p < 0.05) between taxonomic and phylogenetic richness. Both fish taxonomic and phylogenetic β-diversity values were low (<0.33) with high turnover patterns (72.23% and 67.42%), underscoring the necessity for local managers to protect entire water areas to maintain or enhance community diversity. Only taxonomic and phylogenetic richness are significantly positively (e.g., water depth) and negatively (e.g., turbidity) affected by different environmental variables. Environmental heterogeneity was the dominant factor influencing both total β-diversity and turnover processes at the taxonomic and phylogenetic levels, while spatial distance primarily influenced the nestedness process. These findings are critical for elucidating changes in patterns of fish community diversity and their driving factors in the context of dam construction, providing a foundation for the conservation and management of aquatic organisms in other rivers, lakes, and reservoirs.