Biofluorescent response in lumpfish Cyclopterus lumpus to a therapeutic stressor as assessed by hyperspectral imaging

The demand for lumpfish (Cyclopterus lumpus) as a biological control for salmon lice is increasing. However, lumpfish welfare is considered a limiting factor within aquaculture operations. Identifying a noninvasive parameter that measures subclinical stress in lumpfish is a key goal for improving their welfare. The lumpfish is documented to emit green and red biofluorescence within the blue shifted light of their environment. Here we show that lumpfish fluorescence responds to a therapeutic stressor within a controlled experiment. Lumpfish (n = 60) underwent a 3-h freshwater bath therapeutant to evaluate whether fluorescence spectra produced by the species respond to external stimuli. Lumpfish were quickly scanned under a hyperspectral camera (400-1000 nm spectral range) prior to and after treatment. The lumpfish were randomly divided into 3 groups with identical treatment. All groups increased fluorescence emissions, though the level of change depended on whether the averaged, red, or green spectra were analyzed; the control group (n = 20) remained constant. All lumpfish emitted green fluorescence (~ 590-670 nm) while a portion (49%) produced red fluorescence (~ 690-800 nm). As lumpfish fluorescence shifts in response to the applied stressor, this study provides insight into how fluorescence may be incorporated into the welfare management of lumpfish.