A fear of artificial lighting - 'Fish' ecosystem destruction
In the case of fish, there are fish species that gather in the light, and fish that avoid light, and excessive light interferes with growth and spawning, or induces excessive spawning. The fish with regurgitated instincts such as salmon and herring are relying on the lights to feed the carnivorous species because of night lighting. Freshwater fish, canary, and green hydra are also gathered in the light, making it easy for the captor to feed. (Fig.1)

Teleost fish reaction to light stimulus depends upon fish physiologic adaptation to ambient light levels prior to exposure to light level changes. Laboratory studies examining the use of artificial light to guide juvenile salmon through migration barriers report measurable differences in fish responses to variations in the quantity and quality of artificial light.

According to Barbara nightingale and Charles simenstad, University of Washington, studies in the Pacific Northwest report potential changes in fish migration behavior and the distribution of fishes in night-lighted areas. Such changes potentially increase mortality risks for salmon, herring, and sand lance. Juvenile chum and their predators, such as hake, dogfish, sculpin, large chinook, and coho, appear to congregate below night security lights with increased light intensities attracting the chum and potentially delaying outmigration. The potential changes in species abundance and dominance resulting from increased prey access under artificial lighting also warrant further exploration. (Fig.2)

Fig.2. Lights along rivers and streams can disrupt predator–prey interactions, such as seals hunting salmon under lights.
Here, an artificial lighting is causing confusion in the fish ecosystem. It should not be forgotten that a fish ecosystem damaged by light pollution can cause human food problems.

Ref: light pollution photo-exhibition http://www.urbanwildlands.org/abstracts.html
Jae Ho Lee, Ph.D 

* Next week’s topic : Light and Plants(Circadian Clock in Plants)

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