How Acoustic Monitoring Could Help Protect Cod Stocks

Heather Goldstone is the science editor at WCAI, the Cape and Islands NPR Station. She holds a Ph.D. in ocean science from M.I.T. and Woods Hole Oceanographic Institution, and spent a decade as an active researcher before leaving the lab to become a writer.

April 04, 2013

Updated July 03, 2023

Here's your science factoid of the day: male Atlantic cod grunt during spawning season. It may sound like useless trivia, but that behavior could help fishery managers better protect cod stocks.

Underwater microphones - hydrophones - installed along the shipping channels leading into Boston already listen for right whales and automatically alert nearby vessels in real time. In fact, you can even get that information on your iPhone.

Now, a new study demonstrates the ability to use a similar method of passive acoustic monitoring to locate aggregations of spawning cod, known as haystacks. During spawning season, male Atlantic cod make a grunting sound that can be detected by hydrophones. The idea is to use underwater gliders equipped with hydrophones to conduct large-scale acoustic surveys. Such surveys would enable scientists to identify when and where cod are gathering to reproduce.

In a management setting, this information could be translated into dynamic closures of these areas to protect the reproductive population from fishermen. Sofie Van Parijs, who leads NOAA's Passive Acoustic Monitoring group, says this approach probably wouldn't reduce either the size of closed areas or the length of closures, but it would ensure that closures were appropriate and as effective as possible. Having real-time data to prove cod are using closed areas for spawning might also garner more buy-in from fishermen.

This scheme won't be going into effect this fishing season, though. Van Parijs says the technology is there, but the funding isn't .. at least not yet. And, of course, a switch to dynamic closures would have to work its way through the fisheries management system.

But perhaps the greatest obstacle to the use of passive acoustic monitoring for conservation of marine species - cod, right whales, or any other - is us. Human activities, from shipping and mining to recreational boating, are making the ocean an increasingly noisy place. Ocean noise can mask the deliberate vocalizations of marine animals. That's obviously a problem for those trying to communicate. It also presents a challenge for those trying to listen in.