How fishing may be changing one fish species at the molecular level
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The pearly razorfish (Xyrichtys novacula) is a small marine animal that lives in sandy coastal waters and feeds on creatures like shrimp. Known locally in Spain's Balearic Islands as raors, it is a popular dish in many homes and restaurants across the region.
Every year during the fishing season, families and fishers head out on the water to catch them. This obviously affects their numbers, but it may also be changing them at a much deeper level.
Hidden cost of the catch
A new study published in the Philosophical Transactions of the Royal Society B found that this intense harvesting is having a hidden, powerful effect on the molecular biology of these fish.
While many previous studies have looked at how fishing alters a fish's DNA, few have studied epigenetic changes. These are chemical tags that act like switches to turn genes on and off without altering the core DNA sequence.
In this study, a team of researchers caught 120 pearly razorfish across three regions in the Balearic Islands. Each site had a heavily fished area and a protected marine reserve, which allowed them to make clear comparisons. In the lab, they analyzed small fin samples to scan for genetic differences and epigenetic marks.
The paper reports that the fish inside the marine reserves were larger and older than those from the exploited populations.
When the scientists looked closely at the fish's core DNA, they found no evidence that heavily fished and protected populations had become genetically different, despite finding that genetic diversity was lower in the fished populations.
Epigenetic changes
However, at the epigenetic level, they found clear signatures of an epigenetic tag called DNA methylation. This occurs when a tiny methyl chemical group is added to a DNA strand and can influence how active a gene is.
The study authors discovered 291 specific DNA sites where these chemical tags differed between the fished and protected areas. "This represents one of the first lines of evidence demonstrating that fisheries can potentially shape epigenetic variation," they wrote in their paper.
The study team found a strong association rather than definitive proof that fishing itself is the direct cause of the DNA methylation changes. They wrote that there could be other possible causes, such as differences in fish crowding, the presence of natural predators, varying food supplies or disrupted social groups within the fished areas.
"Despite this, DNA methylation patterns still differed consistently between protection levels, indicating that observed differences in DNA methylation cannot be explained by demographic structure alone."
While the exact downstream effects of these molecular changes are still unknown, the researchers argue that because protected areas managed to preserve a much higher level of genetic diversity, they act as vital safe zones for the species.
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Publication details
Margarida Barcelo-Serra et al, Fishing pressure induces changes in DNA methylation in genetically homogeneous marine metapopulations, Philosophical Transactions of the Royal Society B: Biological Sciences (2026). DOI: 10.1098/rstb.2025.0031
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Citation: How fishing may be changing one fish species at the molecular level (2026, July 24) retrieved 24 July 2026 from https://phys.org/news/2026-07-fishing-fish-species-molecular.html
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