This is the second in a two part series on reviving Atlantic fisheries. Read the first part here.
In 2012 the Atlantic States Marine Fisheries Commission (ASMFC), responding to tremendous public pressure, tightened the standards to reduce the menhaden harvest by 20 percent. Is this enough to bring the fish back? Franklin expresses concern about whether this can counterbalance the “strip-min[ing] of breeding-age fish. In menhaden’s favor, however, he says, “They’re very fecund.” Laurie advocates a three-year moratorium on harvesting menhaden: “Could we see these square-mile schools reach the Gulf of Maine in three years? Maybe it would take longer, but we should do this experiment. Every fishery from Chesapeake to Eastern Maine stands to benefit.”
Not everyone is so sure. “The bottom line is that there’s no substantial evidence to suggest that menhaden clean the water,” says Ron Lukens, Omega’s senior fisheries biologist. He says that upon maturity menhaden consume mostly zooplankton. They not only don’t substantially reduce algae levels, he says, but through excretion and consumption of large amounts of zooplankton may actually degrade water quality.”
The research on menhaden’s filtering ability is inconclusive, which could be due to limited time spans, seasonal variation, or evolving ecological conditions—including a drop in their own numbers—that have altered their feed and habitat. Laurie says that making effective use of the fish’s filtering capacity involves working with its life cycle.
“The young fish seem to be key,” he says. “Even the transitional juveniles filter 40 percent of the phytoplankton that runs through them. Younger juveniles may be much higher, as the gaps in the gill rakers are much smaller.” It appears that young menhaden, which dwell in inlets and estuaries, are important in that they eat plant matter and therefore clarify the water in these areas, and as prey for rockfish, crabs, and birds like egrets and osprey. The adults, which live in the open sea except to breed, are significant as food for larger predator fish and for maintaining the population of young fish that eat algae. Laurie notes that current catches contain few menhaden of three years or older, suggesting that numbers of breeding-age fish are way down.
The Big Picture
Research in marine systems increasingly points to the importance of ecosystem-based management—and the role of forage fish. For example, scientists in Namibia have traced periodic episodes of putrid gas accompanied by fish die-off along the coast to depleted sardine stocks. Sardines eat plankton, and when their numbers drop plant matter accumulates and ultimately implodes, releasing hydrogen sulfide and methane.
Such knowledge is starting to inform fisheries management. A menhaden “grazing” plan would join other ecosystem-based marine programs, including efforts in several states to bring back oysters (powerful filter feeders) and campaigns in New England to recover river herring and alewives—other small, school fish that are food sources for larger fish. A 2012 report from the Lenfest Ocean Program found that forage fish are worth twice as much in the water—in their role in the ecosystem—than as commercial catch. The panel also determined that conventional management did not reflect their foundational role in oceans and estuaries, indicating a direct economic benefit to considering these species’ value to the food chain.
Many believe the payoff transcends the balance sheet. Says Gordon, “Successful efforts to conserve Atlantic menhaden can quickly revitalize ocean fisheries and coastal ecosystems from Maine to Florida, particularly the Chesapeake Bay.”
For his part, Laurie, working under the auspices of the nonprofit Biodiversity for a Livable Climate, remains busy visiting sites like Bigelow Laboratory for Ocean Sciences in Maine and meeting with the staffs of Massachusetts Governor candidates. And keeping his eye on what he’s working toward. Which looks like this: “The menhaden will bring other predators, including bluefish, which eat just the back end and drop the rest. The ecosystem created from this debris means food for lobster, cod, flounder and other bottom feeders. It is possible that the five-foot Atlantic cod can return, but we must start by converting the algae to oil and proteins. The fishery from the Gulf of Maine to the Grand Banks was once the greatest in history. It could be again if we understand the food webs that made it possible. We need a grazing plan for the East Coast, for sure.”