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Chasing Cod


Tracking a symbolic fish to help save a traditional industry.

On an icy December afternoon, Chris McGuire braced himself on the deck of the Yankee Rose and tossed $300 of electronics equipment into the sea ¬… then watched it swim away.

By spring, 150 Atlantic cod will be carrying these new high-tech tags, providing valuable information about fish behavior that could be critical to the recovery of a struggling species.

Local fishermen have always known that cod return to the waters off the South Shore to breed this time every year – clustering in large numbers, grunting to one another as they get down to business, spawning and providing our best hope of a future for healthy cod populations.

Now, scientists and fishermen are working together to use a sort of “E-ZPass for fish” to gather data about the fishes’ behavior, to better protect this iconic species and the communities that depend upon it.

Concerned commercial fishermen from the Scituate area sought out scientists from The Nature Conservancy, and our partners from UMass Dartmouth and state and federal agencies, to help them map out exactly when and where spawning occurs with the goal of protecting local cod during their spawning season.

“South Shore fishermen approached us to help protect these spawning cod with the future of the fishery in mind, and the collaborating researchers jumped at the chance to work closely with them,” said Chris McGuire of The Nature Conservancy in Massachusetts.

Local fishermen are now seeing cod only during their spawning season in the late fall and early winter, when they used to be abundant for much of the year, explained Frank Mirarchi, who has fished from Scituate Harbor since 1962 and has personally witnessed a decline in cod abundance. Because such factors as warmer seawater and increased predation have made the fishing business on the South Shore ever more uncertain, his son has recently made the difficult choice to leave the fishery, Mirarchi said.

“We hope to provide these fish with protection while they’re vulnerable,” Mirarchi said. “The expectation is that we can provide discrete, small protected areas which will not be disruptive to fishing, while helping the cod stock to recover.”

Each tag emits a coded sound roughly once a minute for up to six years, a signal that’s recorded whenever the fish passes within range of a network of receivers deployed on the sea floor. Each tag has a unique acoustic signature, allowing scientists to track individual fish using the more than 3 million pings these tags will emit over their lifetime. This information allows researchers to visualize the behavior of each fish while on the spawning grounds, and exactly when they leave which is needed for defining a seasonal closure and also to better understand spawning behavior, McGuire explained.

Researchers are also recording the grunting sounds that male cod make to defend their territories and to attract females. Underwater microphones, deployed by federal scientists will record fish vocalizations, which can be used to characterize the timing of the winter spawning period, as well as the relative abundance when compared to past data.

Atlantic cod is central to Massachusetts history – fishing helped build the state’s economy and remains an important industry. However, the cod population has seen steep declines in the last 20 years and despite drastic measures to reduce fishing pressure, remains at historic lows. This year, local fishermen faced a devastating 78 percent cut in the Gulf of Maine cod annual catch limit, which has severely impacted fishermen across the Bay State.

Ultimately, the fishermen and scientists will bring the spawning data to policymakers, to inform future management decisions designed to care for this valuable cod population.

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