By Colleen Quinn
STATE HOUSE NEWS SERVICE
STATE HOUSE, BOSTON -- Gulf of Maine Cod swimming off Massachusetts shores are being tagged with acoustic tracking devices that will help scientists determine when and where the fish spawn.
Scientists, state and federal environmental officials and local fishermen are working together to attach the electronic tags to cod and return them to the water. Fishermen began taking scientists aboard their boats in September to find and tag fish. Cod return to the waters off the South Shore this time of year to breed.
The tags are detected by a series of underwater monitors that pick up the sounds and track the movements of the fish, according to state environmental officials. Each electronic tag emits a sound once every minute, for up to six years, and each tag has a unique sound that allows scientists to track individual fish. The signal is recorded whenever the fish pass within a network of receivers deployed on the sea floor by the Massachusetts Department of Fish and Game's Division of Marine Fisheries.
Department of Fish and Game Commissioner Mary Griffin described the tags as akin to an "E-Z Pass for fish."
Griffin said the tracking project will help scientists determine where cod spawn off the South Shore, and knowing where the spawning grounds are is important for recovery of the population. Dwindling stocks of cod have led federal officials to institute fishing quotas.
"It will help us fine-tune when the spawning is occurring and where it is occurring so we can tailor our regulations and allow a better recovery of the population," Griffin said.
Griffin said fishermen wanted to work with scientists to find ways to restore the sharply declining fish stock.
Some fishermen report seeing cod only during their spawning season in the late fall and early winter, where in the past the fish were abundant most of the year, according to Frank Mirarchi, who has fished out of Scituate Harbor since 1962. Mirarchi was one of the local fishermen who pushed to research the spawning habits of cod.
"We hope to provide these fish with protection while they're vulnerable," Mirarchi said in a press release. "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."
In January 2013, the New England Fishery Management Council slashed the legal harvest of cod in the Gulf of Maine by 77 percent to 1,550 metric tons. It also cut the quota for cod caught on Georges Bank by 55 percent to 2,002 metric tons. The quotas are in effect until 2016.
The acoustic monitoring data will allow researchers to visualize the movement behavior of fish while they are on the spawning grounds, and when they leave the area - information that is needed to define seasonal closures and to better understand spawning behavior, according to environmentalists.
Researchers are also recording the grunting sounds that male cod make to attract females and defend their territories. Scientists from the National Oceanic and Atmospheric Administration deployed underwater microphones to record fish vocalizations, which are used to characterize the timing of the winter spawning period. Researchers from the Northeast Fisheries Science Center use the same equipment to monitor whales.