In the history of mankind, fishing has been around for thousands of years and has served as a major source of food for families and communities. Even in our modern times, almost one billion people depend on fish as a source of protein.
However, The fishing success rate is affected by various factors, such as the presence of fishing grounds and coastline configuration. Aside from these, the phase of the moon also involves fishing due to the intensity of light it provides in the night sky and the changes in tides. It turns out the moon's phases also affect the sound produced by marine organisms depending on their feeding and mating activities.
Effect of Moon Phase on Fish Behavior
A group of scientists wanted to prove that it is possible to learn the whereabouts of marine organisms without actually visually observing them. By listening quietly, experts can glimpse what these creatures are doing in the ocean.
Led by marine biologist Aran Mooney from Woods Hole Oceanographic Institute in Falmouth, Massachusetts, the research team set up several microphones underwater across the globe to 'listen' to marine life.
One revelation from their study is the connection between the activities of the fish and the lunar cycle. It was found out that fish ramp up the sounds they make based on the phase of the moon. They discovered that some of these sounds are loudest during the moon's waning phase.
For instance, the long, thin fish known as cusk-eels strum their muscles like a bass drum as they try to encourage the females to spawn with them. It needs to be a coordinated event since the eggs and sperm get dispersed quickly once released into the water. The waning phase is also a better time to avoid the eggs from being eaten by predators. The predators will find it hard to see when it is too dark, but the sound can still travel very well. In short, producing sounds can help this fish species hide from predators and, at the same time, allow them to communicate with each other.
There are also fish species recorded off the coast of the southern region of India that are noisiest during a full moon. Their sounds are produced due to the vibration of their swim bladders, the organ that helps them float in water. Scientists believe that the vibration happens as they eat a species of plankton that glistens in the moon's light.
How Can This Help in the Conservation of Coral Reefs?
From these observations, the research team concluded that the eating behavior of some fish is related to light. They investigated further by recording the sounds in marine habitats threatened by pollution and climate change and compared them to their previous soundscapes. For instance, they recorded a sound on the coral reef off the U.S. Virgin Islands in 2013 when marine life was still thriving there. It was compared with another recording taken in 2022 when the area had become degraded.
To restore the coral reef, Mooney set up underwater speakers that broadcast the sound recording of the old, healthy coral reefs hoping to attract the larvae that would build up new coral. Compared to degraded coral reefs where sounds are not played, the acoustically enhanced reef will get more settlement.
If their experiment becomes successful, the old recordings of the previously healthy marine ecosystem will not just be a part of the past. Instead, they could hold the key to restoring ocean life.
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