Exposure to Increased Ambient Ultraviolet B Radiation has Negative Effects on Growth, Condition and Immune Function of Juvenile Atlantic Salmon (Salmo salar)

Abstract

Atlantic salmon (Salmo salar) parr were exposed in two outdoor experiments, ranging in duration from 52 to 137 days, to spectral treatments: (1) natural sunlight (=present ambient UVB level), (2) solar radiation supplemented with enhanced UVB radiation from lamps simulating 20% or 8% stratospheric ozone loss or (3) UVB-depleted sunlight achieved by screening with Mylar-D film. The growth, condition and immune function of the salmon were quantified after treatments. Exposure to enhanced UVB radiation retarded growth, and decreased hematocrit value and plasma protein concentration. Further, enhanced UVB radiation affected plasma immunoglobulin concentration. The results demonstrate that juvenile Atlantic salmon are not able to fully adapt to increased ambient UVB levels in long-term exposures, and the interference with immune system function suggests a negative effect of UVB on disease resistance in Atlantic salmon.

Effects of UV Radiation and Diet on Polyunsaturated Fatty Acids in the Skin, Ocular Tissue and Dorsal Muscle of Atlantic Salmon (Salmo salar) Held in Outdoor Rearing Tanks

“…The conclusion that the health of juvenile Atlantic salmon is reduced under mildly increased UV is supported by findings of a companion study (12). In a parallel series of measurements, with another subset of fish exposed to higher UV levels than was the case in this experiment, the authors (12) found decreased weight, hematocrit values and plasma protein concentrations in juvenile Atlantic salmon.…”

“…It is well established that stress, and especially changes in nutritional status in early life stages, can have unforeseen but significant fitness consequences in fishes, birds and mammals later in life (46,47). The results of this study, a companion study (12) and the work of others (44) all suggest that unprotected juvenile Atlantic salmon may experience negative effects (immune and behavioral responses, changes in fatty acid profiles) following exposure to UVR and that their growth is slightly reduced (this study). Other studies have reported that exposure to UVR can have negative effects on the skin and eyes of various fish species, including salmonids (see above).…”

“…There were eight tanks (experimental units) corresponding to the eight possible feed · UV treatment combinations. Additional details of the experimental setup and conditions can be found elsewhere (12).…”

“…Exposures ran from 30 April to 26 September 2002. Specific exposure regime details can be found elsewhere (12).…”

Carotenoids in Aquatic Ecosystems and Aquaculture: A Colorful Business with Implications for Human Health

“…Although the direct effects of exposure to UV radiation are likely minimal within the context of all the other environmental factors that cause very high levels of egg and larval mortality in marine organisms, studies have shown that UV-induced egg mortality could be as high as 32.5% for the planktonic copepod Calanus finmarchicus and considerably less (1.2%) for the Atlantic cod Gadus morhua in the waters of the estuary and Gulf of St. Lawrence, Canada (Browman et al, 2000). Other direct effects of UV exposure on fish eggs or larvae include malformation (Dong et al, 2007), retarded growth (Jokinen et al, 2008), lesion of skin, eyes, and brain (Blazer et al, 1997;McFadzen et al, 2000), and weakened immune system (Markkula et al, 2005, 2006). These pernicious effects may be higher for fish larvae that are often present in surface waters since UV-B (λ = 280-320 nm) exposure induces DNA damage in a variety of fish larvae such as Atlantic cod, northern anchovy Englausis mordax, icefish Cephalus aceratus and Japanese medaka Oryzias latipes (see Fukunishi et al, 2012 for references).…”