Pearl razorfish begin their lives as females before some naturally transform into males. -National Geographic photo
Fishing is known to reduce fish populations and alter the size and lifespan of fish found in the wild. But a new study suggests the effects may go far beyond that.Researchers have found that overfishing may alter the biology of the pearl shaverfish at a molecular level.
The study says intense fishing pressure is linked to changes that may affect how fish genes work.The findings, published in the journal Philosophical Transactions of the Royal Society B, provide some of the first evidence that hunting can influence epigenetic changes.
Pearl razorfish
The pearl barberfish (Xyrichtys novacula) is a small marine fish that lives in sandy coastal waters. It feeds on small marine animals such as shrimp and other small creatures found on the sea floor.
According to National Geographic magazine, every pearl moose fish is born female. As they grow, some of them naturally turn into males. The dominant male defends a shared territory with several females, which helps maintain order in the group and reduce premature sexual changes among younger females.In Spain’s Balearic Islands, the fish is known locally as raur. It is considered one of the famous seafood. Every year, many fishermen and local families participate in the hunting season to catch it.
Because of their popularity, this species faces intense hunting pressure in some areas. Scientists wanted to know if this pressure affected fish in ways beyond simply reducing their numbers.
Protected areas versus hunting areas
To study this, the researchers collected 120 pearl moose from three different regions in the Balearic Islands. Each region included two types of sites.In the first area hunting is allowed and fish are caught regularly.
The second area is a marine reserve in which fishing is prohibited.Scientists collected small samples of fish fins and examined their DNA and epigenetics in the laboratory.
DNA vs genetics
DNA contains genetic information that is passed from generation to generation. Meanwhile, epigenetics adds small chemical tags that can control how active certain genes are. These marks act as switches that can turn genes on or off or change how strongly they work.One common type of epigenetic change is DNA methylation. DNA methylation occurs when a small chemical group called a methyl group attaches to DNA.This can affect how a gene works and can sometimes help organisms respond to changes in their environment.
DNA differences
When the researchers compared fish from protected areas with those from heavily fished areas, they found no evidence that the two groups had become genetically different.
This means that extensive fishing has not changed the actual DNA sequence of the fish.However, the study found that fish living in heavily fished areas have less genetic diversity than those found within marine reserves.The researchers also found that fish living within protected areas were generally larger and older than fish found in places where fishing was common.Although the DNA itself has remained largely the same, researchers have discovered important differences in DNA methylation.They identified 291 specific sites in DNA where these chemical markers differ between fish in protected waters and those in heavily fished areas.According to the researchers, “This represents one of the first lines of evidence demonstrating that fisheries can shape epigenetic diversity.”The results suggest that hunting may be linked to changes in the way genes are regulated, even if the genes themselves remain unchanged.
Hunting is not the only reason
The study found a strong link between hunting pressure and DNA methylation, but it does not prove that hunting directly caused these changes, the researchers said. They suspect that other environmental factors could also be involved.For example, fish living in heavily fished areas may experience different population densities, food availability, or numbers of predators that can influence epigenetic changes.In the study, DNA methylation patterns remained different even after demographics were taken into account. This means that differences in the number or age of fish alone do not fully explain the molecular changes observed in the study.
