Fish Are Losing Their Sense Of Direction Due To Smog

Stewart Gasper

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Stewart Gasper

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    Smog has become the most toxic hallmark of the oceans and a serious threat to its inhabitants. Many species wander lost without being able to use their abilities to communicate, navigate and survive. Faced with the roar of ships and the smells they expel, sometimes they neither hear nor smell what really interests them to orient themselves and capture the proximity of a predator.

    It is a danger, however, that for decades it has gone unnoticed because it used to focus on uncontrolled fishing or the disappearance of reefs. It is only now when scientists have begun to detect that fish are losing those senses that help them communicate, navigate and survive.

    Biologist Kieran Cox, from the University of Victoria in Canada, has conducted a meta-analysis based on 42 studies that show how the aquatic environment is increasingly bombarded by a variety of acoustic pollutants whose range and intensity have continued to increase in the last decade negatively affecting the behavior and physiology of fish. The greatest danger is seen in their ability to feed, the risk of predation and reproductive success. In addition, it was shown that anthropogenic noise increases hearing thresholds and cortisol levels of numerous species.

    For Jennifer Kelley, a biologist at the University of Western Australia in Perth, the repercussions are serious: “When these species settle in wrong homes or do not recognize predators, the entire ecological system will be altered and we will see how it extends to the way in which individuals interact.”

    Fatally approaching predators

    As an example, the clownfish is already beginning to suffer the effects of ocean acidification and it is hard for him to find a safe place in coral reefs, something that behavioral ecologist Danielle Dixson proves in studies he directs from the University of Delaware, in Newark (USA): “Smell fails and fatally approach predators.” The increasing carbon dioxide emissions are becoming more and more acidic in the oceans and in a few decades could lead to an increase in the mortality of the larvae, according to an article published in Ecology Letters.

    The root of the problem would be in the brain, since acidified water alters the functioning of a chemical receptor known as GABAA. This same cause could also reduce the olfactory capacity of other larger species, such as sharks, weakening one of its main food detection systems, according to a study that appears Global Change Biology.

    In the case of cod, which use sound to communicate, human noise is interfering with its migrations and they find it difficult to distinguish acoustic signals from the ocean between the uproar that arrives from recreational boats, commercial boats and other sources. Cox and his team conclude most species in marine ecosystems are sensitive to these sources of noise and the consequences could be extremely serious.”These findings should serve as a warning to stop the current trajectory.”