Bay Journal

Menhaden stock perplexes fish managers

Too few of the forage fish or too many rockfish?

  • By Karl Blankenship on September 01, 2004
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Menhaden trapped in an impoundment net. (Kent Mountford)

After four decades of fishing the Bay, Jim Price says he is ready to hang up his rod and reel, at least when it comes to striped bass. The fish—a species he has prized and studied for years—are now too sick, and too skinny, to be worth catching.

I spent my whole life working with this fish,” said Price, a onetime charter boat captain. “But I have no desire to go out here and catch a rockfish. Those days are over.”

Almost a decade ago, Price began raising concern that the Bay’s most popular recreational fish was running out of menhaden, a small, oily fish, to eat.

Many say the species has been overharvested in the Bay by a commercial fishing industry that has consolidated largely in Virginia while most other states have closed their waters to commercial menhaden fishing.

Menhaden are an important forage fish for striped bass, as well as other predators such as weakfish and bluefish. But everyone agrees the numbers of young menhaden in the Bay have been at low levels for years, even as striped bass populations have mushroomed.

The lack of menhaden is blamed for “skinny” rockfish in the Bay. Studies show that striped bass of the same age are smaller today than they were just 15 years ago. Some claim the Bay’s most prized fish is so stressed and underfed that they have become susceptible to mycobacteriosis—a potentially lethal disease that can cause ugly lesions on fish—which infects half or more of the Bay’s rockfish population.

As the situation worsened, recreational anglers have increasingly pressed for efforts to curtail the menhaden fishery, with efforts ranging from a “save the stripers” petition drive to unsuccessful legislation in Virginia this year to clamp down on the fishery. “You’ve got a lot of people angry here in the Bay area,” Price said.

But, some scientists say, there is a problem with the overfishing scenario. It may not be true. In fact, assessments of the menhaden spawning stock show it is healthy—and has been for years.

The numbers of young “peanut” menhaden are clearly near record lows in the Bay, but scientists say there are potential causes other than the menhaden fishery—including the possibility that the Bay’s huge striped bass population may be taking too big of a bite out of the menhaden population.

“People are really, really upset and they want something to be done,” said Matt Cieri, a fisheries biologist with the Maine Department of Marine Resources. “The unfortunate thing is, I’m just not sure what that something is, other than trapping and trucking a whole bunch of menhaden from New Jersey down into the Chesapeake.”

After years of prodding, the Atlantic States Marine Fisheries Commission—a multistate organization responsible for managing migratory species—plans to hold a workshop this fall to deal with the question of whether the Bay is running out of menhaden, and if restrictions are warranted for the commercial fishery.

To some, the ASMFC’s willingness to take a broad look at the issue signals that it is ready to act. “I think it has the potential to lead to some significant changes in the way the fishery is managed and to give at least some interim protections to the menhaden stock and the fish that prey on them,” said Ken Hinman, president of the National Coalition for Marine Conservation.

Others doubt such a workshop can do much more than highlight how much scientists don’t know about the issue. “Having a workshop,” said Cieri, who chairs the ASMFC’s Menhaden Technical Committee, “is not going to change how much data we have to make decisions with.”

Atlantic menhaden historically have gotten little of the public attention showered upon other Bay dwellers, such as striped bass, oysters or blue crabs. For most people, menhaden may be the most important Bay fish they’ve never heard of.

They support the largest commercial catch in the Bay, accounting for about 80 percent, by weight, of the total commercial landings.

Menhaden have been harvested since colonial times, when they were used for fertilizer. Since the 1800s, they have been fished commercially for such purposes as oil, fertilizer and animal feed.

In more recent years, much of the menhaden harvest has gone for aquaculture feed, although their Omega 3 oils are also being used as nutritional supplements for humans because of their multiple benefits, including lowering the risk of heart disease.

But their ecological role is every bit as important as their economic role. While oysters tend to get attention for their filter feeding ability, menhaden are also major grazers of the Bay’s prodigious supply of algae.

They are not picky eaters. Menhaden will graze huge amounts of small, less desirable types of algae that other fish won’t touch—adults can be seen swimming in tightly packed schools, their mouths wide open to screen phytoplankton.

Scientists have estimated that a healthy, algae-grazing menhaden population might remove 10 percent or more of the Bay’s nitrogen, although such estimates remain controversial. Because of that potential, even wastewater treatment plant operators in the past have urged the ASMFC to consider reduced catches.

But menhaden are also a major biological engine that propels the Bay ecosystem. They rapidly turn algae into food—small menhaden can grow by 1 millimeter a day—for many of the Bay’s predatory fish. Because they are rich in oils, menhaden are considered to be especially nutritious for other fish, and are credited with helping striped bass build fat reserves before winter.

Studies in Maryland show that the menhaden content in striped bass diets has dropped sharply in recent decades. In the late 1950s—when menhaden stocks were at their highest in recent history—they accounted for nearly 80 percent of the diet for striped bass more than 3 years old. That fell to about 65 percent in the early 1990s, and to about 20 percent now.

Today, 3– to 6-year-old Bay-dwelling striped bass on average weigh 10–15 percent less than they did in the 1980s. Other studies show that body fat reserves in striped bass have also dwindled.

Also dwindling is the supply of menhaden, especially those younger than 2 years old. These are the ones preferred by most of the striped bass living in the Chesapeake, where rockfish spend the first several years of their lives. The number of small fish entering the menhaden population, known as “recruits” has been at near record low levels for more than a decade.

The sad state of striped bass has increased scrutiny on the menhaden fishery, the activities of which are highly visible.

The commercial fishery uses spotter planes that locate schools of menhaden and notify ships, which encircle entire schools with huge nets, forming a purse or bag that allows the entire school to be pulled from the water.

But many scientists say the link between menhaden fishery and ongoing poor menhaden recruitment is anything but clear-cut, especially as the spawning stock of menhaden has been at healthy levels in recent years, according to ASMFC stock assessments.

Unlike striped bass or shad, scientists believe there is no discreet Chesapeake menhaden stock that is responsible for maintaining the Bay’s population.

Schools of adult menhaden swim along the coast from late winter to early summer leaving a trail of eggs as they go. The eggs and larvae move with currents for up to three months before washing into coastal bays and estuaries where, if they survive, they are considered recruits into the menhaden population.

Because menhaden spawn as a single, coastal stock with their eggs randomly dispersed, any problem with recruitment should be reflected coastwide, many scientists insist—not just in the Bay. Yet some surveys suggest that the numbers of young have increased elsewhere. In lower New England, said Doug Vaughan, a fisheries scientist with the National Marine Fisheries Service who assesses the health of the menhaden stock, “the indices have been at historic highs over the last five to eight years.”

But, he added, because the bulk of the menhaden population is in the mid-Atlantic, good recruitment in New England has less of an impact on the overall population.

Vaughan and others suspect the reason for the Chesapeake’s poor menhaden recruitment in recent years rests not with the spawning stock, but with factors more restricted to the Bay.

That could include things like poor water quality in the Chesapeake. Some suggest that the focal point for menhaden recruitment—which historically has been centered in the Bay and North Carolina estuaries—might be shifting farther north for some reason. Or other issues may be important.

For instance, an analysis of decades of spawning and weather data by Bob Wood, a climatologist with the National Oceanographic and Atmospheric Administration’s Chesapeake Bay Office, suggests that menhaden recruitment in the Chesapeake—as well as striped bass recruitment—is heavily influenced by regional weather patterns.

When a high pressure system, known as the Azores-Bermuda high, dominates the region’s weather patterns in March—usually signaling an early spring—it’s good news for menhaden as well as other ocean spawners. But when a competing system, dominated by a high pressure system known as the Ohio Valley High, dominates, it’s good for striped bass and other anadromous fish. In general, that pattern has been more favorable for striped bass in recent years than for menhaden, Wood said.

That could explain why, although the ASMFC’s assessment continues to find healthy spawning stocks, actual recruitment has been low.

“In terms of spawning stock, the numbers are incredibly good,” Vaughan said. “But it is the survival through to recruitment which seems to be the bottleneck.”

Another possibility is that past emphasis in managing for a large striped bass stock after the population crashed—forcing a closure of the fishery in the late 1980s—has produced a population so large it is putting other species at risk. And not just menhaden, but other fish that also rely on menhaden for food.

“This isn’t just about menhaden and striped bass,” Cieri said. “It is also about the effects of striped bass on the availability of prey for weakfish and bluefish, as well as some of the marine mammal populations. Do you want more striped bass, or do you want more bluefish?”

For all the concern about menhaden, they remain one of the most numerous fish in the Bay. The question for those who worry about the size of the fishery is whether menhaden are being managed in a way that allows them to perform all of the economic and ecological jobs that people expect of the small fish.

Critics say the stock assessment is aimed primarily at measuring whether the menhaden spawning stock is large enough to support the fishery, and that it does not adequately account for the needs of predatory fish. Although the ASMFC’s most recent menhaden management plan— completed more than three years ago— calls for taking the ecological role of menhaden into account, the plan specifies no actions to make that happen.

The ASMFC is supporting the development of a complex multispecies computer model focused on menhaden, but it is not expected to be completed for more than a year.

Fishery critics also contend the population baselines used to measure healthy menhaden populations are based on estimates since the 1950s. Before that time, evidence suggests the menhaden population may have been much greater. “We may have actually been overfishing this stock for 40 to 50 years and not realized it,” said Bill Goldsborough, senior scientist with the Chesapeake Bay Foundation.

There is also concern from some scientists, environmental groups and recreational anglers that the stock assessment focuses on the entire East Coast, and therefore does not address population health in local areas, such as the Bay. The intense fishing pressure in the Chesapeake, they say, could lead to localized depletion of menhaden stocks, and too few fish for other species to eat.

Once, the catch of menhaden was distributed all along the coast. As recently as 1981, menhaden was processed at 11 East Coast plants. Today, only two processing plants are left, on in Reedville, VA, and one in North Carolina. About 60 percent of the entire menhaden East Coast catch comes out of the Bay—but the total catch is declining.

Two independent peer reviews of the ASMFC’s stock assessment in recent years have raised the question of whether localized depletion could be an issue.

Alexi Sharov, a fisheries biologist with the Maryland Department of Natural Resources and a member of ASMFC’s Menhaden Technical Committee, said it is hard to know whether that’s the case because no one has ever adequately monitored the rate at which menhaden migrate in and out of the Bay.

“The perception is that there is a constant exchange,” he said. “The schools are moving in and out and there is a constant replenishment.” In fact, Sharov said, no one really knows whether most of the menhaden move into the Bay in the spring and stay there, or whether large numbers are constantly moving in and out during the summer, replacing those caught in the fishery. “That is one of the black holes that really preclude us from making any conclusions,” Sharov said.

In the face of such uncertainties, the groups pushing for ASMFC action say that management should take a “precautionary approach.” They call for reducing the overall menhaden catch and incorporating numeric catch limits in the menhaden fishery management plan—right now the plan does not set a specific maximum harvest. They also advocate spreading the menhaden catch over a broader geographic area.

In addition, they would like to limit the harvest of menhaden which have not lived long enough to reproduce—those 2 years old or younger. Right now, most of the fish caught in the Bay are 2 years old. Raising that to 3 years old would give the menhaden a chance to spawn at least once.

While factors such as climate may be an important influence on recruitment, Goldsborough and others say that increasing the spawning stock may provide some help for recruitment in marginal years. People can’t do much to control variables such as the weather, he said, but they can manage the catch. “You control what you can control,” Goldsborough said. “And the more adults you build into the population, the greater buffer you have against poor recruitment.”

Most of the immature striped bass that live in the Bay eat smaller menhaden—which are not targeted by the fishery. But Goldsborough said controlling the catch of age 2 menhaden would also increase the food supply for larger striped bass migrating in and out of the Chesapeake.

Besides reducing the menhaden catch, some are also open to increasing the striped bass catch to reduce their menhaden demand, perhaps by reducing the minimum catch size for striped bass below the current 18 inches.

In the late 1970s and early 1980s—before the fishery was closed because of a stock collapse—it was legal to catch striped bass that were 12 inches long. When the fishery was reopened, the minimum size was raised to 18 inches to protect the stock.

But an 18-inch fish demands dramatically more food than a 12-inch fish. Even if the striped bass population had not increased, raising the minimum size limit would have increased their food demand threefold, according to estimates by Jim Uphoff, a fisheries biologist with the Maryland Department of Natural Resources.

Price, the former charter boat captain, said that protecting striped bass may have worked too well. Two decades ago, he pushed to protect the striped bass as a threatened species. Now, he not only blames too few menhaden for striped bass woes, but also striped bass abundance.

“If you look at the data, striped bass abundance has had an influence on menhaden abundance ever since we kept records,” Price said. “I think you have to manage both.”

Not everyone who wants to protect menhaden agrees with that view. Hinman, of the National Coalition for Marine Conservation, argues that heavier fishing on striped bass will only reduce their abundance as well. “We could have too many striped bass in the Bay for the number of menhaden that are there, but that doesn’t mean we shouldn’t have that many striped bass in the Bay. It could be that we should not be fishing for menhaden primarily in the Bay.”

To many, the upcoming workshops are welcomed because they may hasten the arrival of a new era of multispecies fisheries management.

Traditionally, fish species are managed individually, as though what happens to one species will not impact another. The poor status of many fish stocks has helped to promote the concept that interrelationships between species need to be accounted for in fisheries management.

In fact, the Bay Program’s Chesapeake 2000 agreement called for Bay fishery management to address multispecies issues—starting with the menhaden plan.

But some say the debate about menhaden and striped bass illustrates that multispecies management is no panacea. Fishery managers already face tough questions in determining how much of the catch should be allocated among recreational and commercial fishermen, as well as among states. Multispecies management makes that even more difficult because it pits species against species—along with their stakeholders.

“You have a stakeholder in one fishery having a say in another fishery,” said Tom Miller, a fisheries biologist with the University of Maryland’s Center for Environmental Science. “Those are going to be very challenging questions.”

Managers, with uncertain data, are forced to pick winners and losers. The new watchword for fisheries management is, when faced with uncertainty, to be “precautionary.”

But in this case, Miller asked, does precautionary mean protecting menhaden from commercial fishermen—or from striped bass? The questions go on. Whose stake is more important—that of recreational anglers who fish for striped bass or that of a small town that depends on menhaden for its living? How many menhaden should be preserved to help filter the Bay?

Miller, who served on the peer review panel that examined the ASMFC’s recent menhaden stock assessment, said so many questions remain about menhaden that it may be hard to reach definitive answers. The ASMFC’s Menhaden Technical Committee recently outlined a $1-million-a-year research program aimed at clarifying what it considers to be key issues to improve menhaden management.

“I don’t think there is a golden treasure trove of data out there waiting be correctly analyzed and brought to the table that is going to answer all of the questions,” he said.

It’s unclear whether recommendations from a workshop could lead to acceptable management action.

For example, the ASMFC may not be able to force the menhaden catch to be spread out. Most other coastal states have closed their waters to menhaden fishery: Only Virginia and North Carolina waters—as well as federal water more than 3 miles offshore—remain open. The ASMFC has no authority to order states to allow the menhaden boats to fish.

Many consider it unlikely that ASMFC would allow a greater striped bass harvest in the Bay. Anglers in many coastal states believe their supply of large fish hinges on large stocks in the Chesapeake.

Some worry that the stakes of any decision could be huge. Instead of moving toward addressing multispecies concerns, they worry that a premature action by the ASMFC could actually hinder multispecies management.

“There is always a fear that some people, in a desperate attempt to do something to rectify the problem in the Chesapeake Bay, may impose management measures that may or may not be effective,” Cieri said. “If those management efforts end up being challenged, as I’m sure they will be, one wouldn’t want to see a setback in ecosystem management because someone jumped the gun.”

Others, such as Price, who has pushed for action for a decade, worry about what will happen to the Bay’s fish if nothing is done. He worries that if striped bass are not controlled, and menhaden fishing reduced, hungry striped bass may begin threatening other species through increased predation. “If these workshops can’t come up with some recommendations, I’m going to be ready to throw in the towel,” he said.

The dates for the ASMFC workshops are Oct. 12–14. Check www.asmfc.org for details.

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About Karl Blankenship

Karl Blankenship is editor of the Bay Journal and executive director of Chesapeake Media Service. He has served as editor of the Bay Journal since its inception in 1991. .(JavaScript must be enabled to view this email address).

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