Cod May Have Regional “Accents” That Could Spawn Trouble When Breeding

Recording fish communication could help scientists learn more about the impact of underwater noise pollution

Adrian Mohedano via Flickr

Scientists have known for years that the sounds pollution of our lakes and oceans can interfere with some aquatic species’ ability to navigate their watery world. But echolocating whales and dolphins aren’t the only sea creatures who can “talk” to each other—some fish species, such as cod, can do it, too. Now, researchers studying these fish suggest that cod could have accents of a sort depending on where they hail from. Coupled with increasing underwater noise, these different voices could make it harder for some of these fish to breed.

Cod may not be the most brilliant fish in the sea, but when it comes to chatting, they are pretty verbose. During mating season, male cod can vibrate their swim bladders to produce a varied series of thumps and growls that they use to convince females to release their eggs for fertilization, Jonathan Amos reports for the BBC.

"Cod tend to hang around near the bottom at spawning time, and then a female and a single male will rise towards the surface and he's got about ten seconds to get his love song right,” University of Exeter researcher Steve Simpson tells Amos. “If he does, she'll release her eggs; get it wrong and she'll swim back down to the bottom."

Because cod tend to return to the same breeding ground where they were born, different groups appear to have developed their own kinds of mating calls—sort of like regional accents. While that can help these fish communicate with each other come mating season, it can be a serious barrier for those who have migrated away from their home territory, Victoria Lindrea reports for CNN.

“Recordings of American cod are very different to those from their European cousins, so there is a precedent,” Simpson tells the Press Association. “This species is highly vocal with traditional breeding grounds established over hundreds or thousands of years, so the potential for regionalism is there.”

While these breeding grounds have stayed the same for a long time, the ocean is rapidly changing as climate change continues to alter the world’s ecosystems. As water temperature continues to rise, the cold-water-dwelling cod are starting to migrate north, bringing previously distinct populations into closer contact with each other, the Press Association reports. That could mean that these migrating fish might have trouble breeding with groups that have lived in particular regions for a long time due to a difficulty understanding their cousins’ “accents.”

In addition to conflicting vocalizations, Simpson is concerned that the cod’s mating calls are being drowned out by boat traffic. Past studies have shown that ships traveling near coral reefs can throw off tropical fish who also use sound to communicate, but to date there has been little research on the effect the shipping industry may have on the seascape around the United Kingdom, Lindrea reports. Simpson and his colleagues are dragging microphones through waters in the region to see how these fish are chatting with each other in hopes of analyzing their interactions and determining whether their calls are being drowned out by passing ships.

“Listening to fish is a really good way of surveying what is there, and what their behavior is,” Simpson tells the Press Association. “If we value our fish stocks—or our Friday night fish supper—we need to understand this.”

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