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Scientists investigate ecological value of menhaden

With catch limits on Atlantic menhaden being tightened to end overfishing, a new study is getting under way to look at just how many of the little oily fish need to be left in the water to maintain the health of other fish in the Chesapeake Bay and along the East Coast.

Under a $320,000 grant from the Lenfest Foundation, fisheries scientists from the University of Maryland Center for Environmental Science plan to investigate where the balance needs to be struck between fishing for menhaden and preserving them for their value in the ecosystem.

"Management of menhaden has become very controversial because of different views of how we allocate menhaden between commercial and bait fisheries and those left in the ocean to serve as prey for striped bass and other predators," said the study's lead researcher, Tom Miller, director of the center's Chesapeake Biological Laboratory in Solomons. "We're trying to estimate from a scientific viewpoint how much we need to leave for the predators to fulfill other important roles in the ecosystem."

More than 300 million pounds of menhaden are caught annually and processed at a plant in Reedville, Va., into meal and oil for livestock and fish food, and for Omega-3 fish oil supplements. Many also are harvested for use as bait in crab and lobster fisheries

But the fish are a vital food source for larger fish such as striped bass and bluefish, for marine mammals and for birds. They also feed on phytoplankton, the microscopic aquatic plants that cause algae blooms every summer, though the significance of their role in maintaining water quality is disputed.

With the coast's menhaden stocks said to be at their lowest level in more than 50 years, the Atlantic States Marine Fisheries Commission last week imposed its first-ever coastwide catch limit on the fish.

Though fishermen said the 20 percent catch reduction was onerous and unneeded, officials said at the time they were acting out of concern for ensuring that menhaden continue fulfill their role in the ecosystem. But uncertainties remain about what size population would be ideal under those circumstances.  The commission plans to conduct a new full-scale scientific assessment of its status in two years.

The UM scentists's research is independent of that assessment, but still meant to help fisheries managers.  They aim to get a better hanlde on menhaden's value as a forage fish and as a filter feeder, and give fisheries managers some guidelines on where to set commercial catch limits to ensure that those other two roles are not given short shrift.

 "In short our work will try to provide a common currency on which the fishery value, forage value and ecological values of menhaden can be compared and evaluated," Miller said in an email.  "In particular we want to try and quantify the trade-offs among these three "uses" of menhaden."

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