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.

Hidden in plain sight: hyperspectral documentation of complex biofluorescence produced by the green sea urchin (Strongylocentrotus droebachiensis).

Biofluorescence in echinoderms is largely unexplored, and even though the green sea urchinStrongylocentrotus droebachiensisis a well-studied species, the presence and/or function of fluorescence remains very poorly understood. Hyperspectral imaging was conducted on adult sea urchins (N = 380) while fluorospectrometric analysis was conducted on sea urchin coelomic fluid (N = 30). Fluorescence was documented in both the spines and coelomic fluid ofS. droebachiensis. Intact spines exhibited a low intensity green emission (∼550-600 nm), while broken spines averaged a high emission peak in the green spectrum (∼580 nm). Sea urchins produce a red exudate with a pronounced emission peak (∼680 nm) with a shoulder peak (∼730 nm). The sampled coelomic fluid exhibited high variability, with a majority exhibiting a low-level green fluorescence while pronounced emission peaks (N = 5) were found in the red spectrum (∼680 nm). The complex fluorescence produced byS. droebachiensiswarrants further investigation on its applicability for monitoring welfare of sea urchins in aquaculture facilities.

First record of biofluorescence in lumpfish (Cyclopterus lumpus), a commercially farmed cleaner fish.

This study is the first known observation of biofluorescence in the lumpfish (Cyclopterus lumpus). Individual lumpfish were illuminated with blue excitation lighting for photography with both hyperspectral and filtered multispectral cameras. All photographed juvenile lumpfish (n = 11) exhibited green biofluorescence. Light emissions were characterised with two peaks observed at 545 and 613 nm, with the greatest intensity along the tubercles of the high crest and the three longitudinal ridges. Further research on the dynamics of biofluorescence through the lifecycle of this species is required.