Biofluorescence in polar zoarcid eelpouts: The Arctic eelpout <i>Lycodes reticulatus</i> (Reinhardt, 1835) and the Antarctic eelpout <i>Pachycara brachycephalum</i> (Pappenheim, 1912)

Biofluorescence is widespread among marine fish but remains poorly documented in polar ecosystems. Using hyperspectral imaging, we report fluorescent emissions in two polar zoarcid eelpouts. A captive Antarctic eelpout (Pachycara brachycephalum) displayed uniform bright green fluorescence (~500-520 nm), whereas an Arctic eelpout (Lycodes reticulatus) showed weaker patterned emissions (~510-590 nm). Under identical illumination, the Arctic cod (Boreogadus saida) exhibited no detectable fluorescence. Although observations were limited to single individuals per species, spectral peaks substantially exceeded calibration reference values, indicating genuine fluorescent emissions. These observations represent the first reported occurrence of biofluorescence in an Antarctic teleost and expand the phylogenetic distribution of fluorescent fish to include Zoarcidae. The results also demonstrate the potential of portable hyperspectral imaging for non-invasive detection of fluorescent traits in cold-adapted fish.