Fluorescent emission profiles reveal interspecific differences in three Danube River Basin sturgeon species.

Biofluorescence is widespread among marine teleosts but has not been reported in sturgeons (Acipenseridae). This exploratory study investigates interspecific differences in fluorescent emission profiles among three Danube River Basin sturgeon species using hyperspectral imaging. We examined 50 juvenile fish from 3 species: the Russian sturgeon (Acipenser gueldenstaedtii; n = 20), sterlet (Acipenser ruthenus; n = 20), and stellate sturgeon (Acipenser stellatus; n = 10). All species displayed green (~ 550 nm) and secondary red fluorescence (~ 615-730 nm) with a minor peak at ~ 650 nm under blue excitation light. Principal component analysis of standardized spectra revealed interspecific species-specific clustering, with PC1 (86.9% of variance) primarily reflecting differences in excitation light reflectance and differentiating stellate sturgeon, and PC2 (3.77% of variance) reflecting variations in green fluorescence intensity and distinguishing A. gueldenstaedtii from A. ruthenus. A. ruthenus exhibited higher fluorescence with lower excitation reflectance, while A. stellatus showed the reverse pattern, and A. gueldenstaedtii displayed consistently stronger emissions across shorter wavelengths (500-530 nm). These findings provide the first evidence of species-specific fluorescent spectral patterns in sturgeons. Such signatures may reflect differences in integument structure and pigment biochemistry, and they hold promise as non-invasive tools for species identification, aquaculture monitoring, and conservation management.