Spying On Fish Love Calls Could Help Prevent Overfishing
According to a group of researchers from the Scripps Institution of Oceanography and the University of Texas Marine Science Institute, spying on fish love calls could protect them from hungry fishermen.
By listening to the loud, unique sounds that fish make when they gather to spawn, scientists have found a way to count how many fish are in a spawning aggregation.
"It can be extremely challenging to get a complete picture of fish spawning events because they can happen over very short to very long times and are often in difficult environments such as murky water," senior author of the study Brad Erismans said. "Our work opens an acoustic window into these exciting spawning events."
Although the team developed this method specifically for corvina fish, it can be adapted to any fish that make courtship calls such as groupers, cod, and croakers.
Each spring, more than two million fish migrate to the Gulf of California. When the males begin to call out to the females, the sound produced is deafening. Using hydrophones (underwater microphones), lead author Timothy Rowell discovered that these fish can make sounds as loud as 192 decibels -- that's enough to damage your eardrums if it were on land.
"It's louder than a rock concert," Erisman said. "It's louder than standing less than a meter from a chain saw."
This boisterous noise-making is dangerous to the fish because it leads fishermen straight to the corvina spawning aggregations.
"Over-harvesting from the aggregation site could result in the functional extinction of the species in the ecosystem, which would have negative effects on the local economy and cause the fishery to collapse," Rowell said. "This is why sustainable harvest levels need to be set. At the moment we do not know what these levels are."
This new acoustic method for monitoring spawning populations could help prevent overfishing in corvina.
"The fishers are by no means the enemy here," Erisman said. "They're actually the ones who have provided us with all the information and access to the resource, and they're the ones most interested in sustainability."
Rowell and Erisman are part of the Gulf of California Marine Program -- an international research group that has created an interactive online tool called DataMARES that allows users to study how corvina populations are changing.
"The idea is we try to bring all the stakeholders, different groups that have a vested interest in the fishery and the environment, together to try to work it out," Erisman said. "And it's nice that science is playing a role in that."