Look what's been happening around the Bay in the past few months:
- Maryland slashed horseshoe crab harvests out of concern there were not enough crabs left for migrating birds.
- Virginia and Maryland restricted clam dredging in grass beds, citing the need to protect those areas for other species, such as blue crabs.
- Some fishermen have raised concerns that there are not enough menhaden in the Bay to feed growing stocks of predators, including striped bass, bluefish and weakfish.
Welcome to the emerging world of "multispecies management" where, it seems, every action cascades though the ecosystem like so many falling dominoes.Multispecies management is a recent concept that recognizes no fish stock exists on its own, but depends on complex interactions with other species, whether for food or habitat.
It is not the rule of today; species are still managed individually. But in small ways, as with horseshoe crabs and grass beds, its day is beginning to arrive, managers and scientists agree. In the future, it could dramatically alter how - and why - fish stocks are managed. That's because multispecies management will bring with it increasingly tough questions: Want lots of striped bass? Fine, but you had better watch out for blue crabs - stripers like to eat the young ones.
If menhaden are fished to their maximum, will it undercut the food supply for striped bass? If so, should the menhaden catch be curbed? Or does a burgeoning striped bass population consume too many menhaden? If so, should their numbers be reduced? And those bay anchovy? That small fish no one pays much attention to? Better keep tabs on them because almost everybody wants to eat them. If they aren't around, well, lots of other things won't be, either.
These are the types of questions ignored by traditional "single species" management. Stock by stock, species by species, fish are usually managed, as one official put it, "with blinders on," as if each lives in its own little ocean. By tracking things such as the number spawned and harvested each year, managers try to set harvest levels that won't jeopardize the stock. Interactions between species are not accounted for.
While there are some success stories - the remarkable comeback of striped bass in the Bay being one of them - single species management is more often the subject of blame than praise.
Last fall, the National Marine Fisheries Service reported that one-third of the nation's marine species were overfished. Closer to home, the Chesapeake Bay Stock Assessment Committee in 1995 determined that eight Bay species were overfished, depleted or severely depleted, while the status of 10 others was unknown. Only two managed species - striped bass and Atlantic menhaden - were considered healthy.
Those types of figures, as well as the rising number of fish classified as threatened or endangered, has given rise to the view that fisheries management needs a broader approach.
From the Pennsylvania farmers asked to reduce nutrients for a cleaner Bay, to volunteers who plant underwater grasses, to environmentalists who want to protect biodiversity, the constituencies watching how fish are managed - and their expectations - are changing. Scientists see multispecies management as the tool that will help better manage, and maintain, healthy populations and ecosystems.
"The Bay Program calls itself an ecosystem management program, but fisheries management certainly is not done in that context in the Bay," said Ed Houde, a scientist at the University of Maryland's Chesapeake Biological Laboratory, who sits on several national panels dealing with fisheries issues. "I think we're going to be forced to move in that direction; it's only a matter of how fast."
One bit of information sums up why many think multispecies management is the wave of the future: In a given ecosystem, the biggest consumer of fish is not the fisherman's net - it's other fish.
That is routinely ignored in fish management today. Already frequently hampered by poor data and political or interest group pressure, past decisions have often resulted in poorly managed or overharvested stocks.
Failing to account for species interactions only compounds the problem.
Management usually seeks to achieve the "maximum sustainable harvest" - the largest number of fish that can be caught while ensuring reproductive capacity - for each individual stock.But that may be impossible, especially where several top predators, such as striped bass, weakfish and bluefish, compete for the same food. Likewise, if the "forage" fish those species eat is also the target of fishing activity, it's unlikely that production of both predator and prey can be simultaneously maximized.
That concept may sound simple, but making such decisions requires a huge amount of information to answer two key questions: Who eats who, and how many?
Because many fish are migratory, they eat different things at different times at different places. They even eat different things at different ages. It's difficult, if not impossible, to manage when these interactions aren't understood. "This isn't rocket science," said Steve Murawski, a scientist with the National Marine Fisheries Service, who has worked on multispecies management models for St. George's Bank off New England. "It's a lot harder."
Rocket science, after all, is physics, where actions follow predictable rules. In biology, people often don't even know the rules. Harley Speir, a fisheries scientist with the Maryland Department of Natural Resources, recalls the time he was on a commercial fishing boat in the Bay in midwinter. When the nets were pulled in and the striped bass hit the deck, they began coughing up squid - something not typically associated with striped bass diets in the Chesapeake.
"They obviously had just eaten them - it doesn't take long for squid to digest," Speir said. "I've never seen that since. Maybe it occurs every year. Maybe it occurs every other year. Maybe it only occurred that one year in the early '80s." That gets to the root of the complexities involved. In the North Sea, which has worked to develop elaborate multispecies assessment models, scientists devoted an entire year to researching the question of who eats who. During "the year of the stomach," thousands of fish were cut open, and the types and ages of the fish inside were analyzed.
A major move into multispecies management would require a similar effort here.
But it isn't that simple. Species move in and out of the Bay at different times of the year, so diets change seasonally. And they could change from year to year. For instance, suggested Tom Miller, a scientist with the Chesapeake Biological Lab, if the fish striped bass normally eat are in low abundance right now - as some suggest - it could be a bad time to analyze stomach content. "What we would measure would be reflective of aberrant conditions," Miller said. "The information wouldn't be suitable to use when the forage base is increased in abundance. A single year's data may be insufficient."
Compounding the problem is that some important fish species are not managed at all - people have no control over their abundance.
Take the tiny bay anchovy, a fish that grows to only a bit longer than 4 inches. It is the Bay's most abundant fish, and almost everything seems to eat it, from birds and animals to other fish. In fact, bay anchovy has been estimated to provide more than half of the total energy intake of predatory fish in the Chesapeake. Surveys seem to indicate that Bay anchovy populations can fluctuate widely from year to year. But no surveys are aimed directly at the fish, despite its importance. That is another kind of data gap that scientists and fisheries managers agree needs to be filled.
Some find room for optimism, though. "Some of the complexity is more apparent than real," said Mike Fogarty, another CBL scientist. While the Bay has many species, he notes, many interact with one another little, if at all. In other words, while striped bass may sometimes eat squid, that interaction, in the big picture, probably isn't significant.
The major activities - those most important for management - may be confined to a "subset of species" in localized areas that could be targeted for more careful study, although Fogarty said it would still take work to determine exactly where those "nodes of interactions" are. "I don't want to minimize how much work would still be ahead in this whole process," he said, "but I do think there is reason for optimism." As interactions are understood, new models could help managers evaluate potential outcomes of various actions. Suppose, for example, striped bass turned out to be an important predator on blue crabs when striped bass populations are high. If so, managers may allow larger harvests of rockfish, or smaller harvests of crabs. "Understanding how the system as a whole is changing might allow you to make different decisions than you would have if you treated each as an independent entity," Fogarty said.
Figuring out how many fish end up in each other's guts is not where the story ends. Fish, after all, do not live on fish alone. They need habitat.
In the Bay, much of that habitat is gone. Beds of grasses that provide food and shelter to many species, especially juveniles, may have once covered 600,000 acres of the Chesapeake. Today, they cover little more than a 10th of that. Chronic summertime low-oxygen levels in deep parts of the Bay squeeze some species out of potential habitats, and reduce the abundance of bottom-dwelling "benthic" organisms that feed other species.
If multispecies management were actively practiced, fish and shellfish may someday be managed not only for harvests, but for their effect on ecosystems.
In the Bay, the classic example would be the oyster. Once, oysters were one of the Bay's most important species; some scientists believe they could filter all of the Chesapeake's water in a matter of days, helping to clear excess algae that degrades water quality. In addition, huge oyster bars aided oyster reproduction - giving oyster larvae, or "spat" a solid surface to latch onto - and provided mini habitats that supported a variety of fish and other species.
If multispecies management had been practiced in the past, fisheries managers may not only have changed the amount of oysters harvested, but how those oysters were taken. Over the decades, dredging techniques flattened oyster bars, ruining much of their habitat benefit. "Bad fishing practices almost certainly contributed to the destruction of oyster reefs," Houde said.
Because of the critical role of habitat, Bill Goldsborough, a fisheries scientist with the Chesapeake Bay Foundation, said true multispecies management means efforts to build healthy fish populations can't be limited to managing catches. Restoring critical habitats as oyster reefs and grass beds, he said, is essential for fostering increased fish production - and fish food.
"The food web, in a sense, is out of balance right now simply by virtue of the decline in both of those resources," he said. "A drop in anchovy or menhaden may be having an exacerbated effect right now by virtue of an increased dependence on them. To me, a comprehensive solution to achieving a stable food web would include restoring SAV and oyster reefs." Much farther down the road is incorporating information about how such Bay Program priorities as nutrient reductions fit in a multispecies management framework. The amount, and type, of nutrients flowing into the Bay can affect the types and quantities of algae produced. Some alga are more preferred by predators - whether oysters, fish or microscopic zooplankton - than others. Likewise, some kinds of zooplankton are more preferred by fish than others.
With multispecies management, it's conceivable that managers could someday decide that the primary aim of menhaden management is neither to support a fishery nor predators. Rather, they could be managed to maximize their ability to "graze" the Bay's excess phytoplankton, thereby improving water quality and - by extension - habitat.
"If they double the biomass of menhaden, which may more than double the filtering capacity of menhaden to remove phytoplankton from the Bay, that might be the kind of decision in multispecies management one would make to have better water quality rather than a different fish catch," Houde said.
In a limited way, management agencies are already in the multispecies arena. Primarily, this comes in the form of managing conflicts - often caused by gear - between fishermen. Typically, this involves fishermen trying to catch one fish hauling up large numbers of a different species in their net, something known as bycatch.
Fishing regulations, particularly those setting gear and season restrictions, are often made to minimize those impacts. "We already practice multispecies management to some degree," said DNR's Speir, "We just don't call it that."
What may be new in the future is trying to better account for food web relationships rather than gear conflicts. In some small ways, the Bay Program is moving in that direction. The blue crab fishery management plan adopted last year contained specific recommendations to bolster underwater grass beds that are important for juvenile blue crab survival. It was the first of Bay fishery management plans - which are signed by state governors - to so specifically recognize the importance of habitat.
Another likely step would be to begin incorporating information about known food web relationships into existing management plans when they are updated. While scientists say it is difficult to perfectly correlate the rise or fall of one Bay species with the rise or fall of another - natural "backup" systems seem to be built into ecosystems - they do know some important relationships exist. For example, the striped bass plan could be changed to require that managers account for the abundance of menhaden or other forage species when setting striped bass harvest levels.
"To date, even though that seems like a common sense approach, to keep track of those things, that does not occur right now," said Robert O'Reilly, of the Virginia Marine Resource Commission.
Another step - one that can be taken without an intensive data-gathering program -could be setting aside sanctuaries as "safe havens" for fish or shellfish. The idea is to reduce harvest pressure in an area where species could, presumably, return to their natural equilibriums among each other.
"These are attempts to have a multispecies management approach without having all the quantitative information, but managers know this is a good thing," O' Reilly said.
Already, Maryland has set aside some oyster areas as reserves, while Virginia has established sanctuaries for blue crabs and clams. Sanctuaries are getting increased attention nationwide, and worldwide, as well. But like other multispecies management decisions, it is not a simple cure-all.
"Sanctuaries are going to be upon us, that's another thing that's inevitable right now," Houde said. "A lot of people want them, including fishermen. Where it breaks down, is when people try to figure out how big the sanctuary has to be, and where it ought to be. Some people that think if we set aside some relatively small little parks, that is going to be sufficient. But many think at least 20 percent of the range of a species would have to be set aside to make it an effective reserve. That can be a huge area, and that means somebody's backyard is going to be impacted." That the Bay states will gradually move toward more multispecies management seems inevitable - the Bay Program's Living Resources Subcommittee this year identified multispecies management as a top priority. The Bay Program's Scientific and Technical Advisory Committee produced a report and recently held a workshop on the issue. But scientists caution that it does not offer a panacea.
With more and better information about species' relationships, managers over time should be able to make better decisions, they say. But better does not necessarily mean easier. There will be winners and losers: If a high value species preys on a low value species, it may make sense to reduce catches of the low value fish to maximize harvest of the preferred species.
"Multispecies approaches reduce the chance of detrimental decisions," Miller said. "But they certainly don't guarantee that you won't have to make difficult choices and won't be faced with times when you are making decisions that strongly impact the livelihoods of people in a way they would rather it didn't."
The payoff may be subtle: A Bay that gradually becomes more diverse - and probably more stable - than it has been. While it's normal for fish populations to fluctuate, most agree that populations for many species have fluctuated wildly in recent decades. Oyster stocks - once the most important Bay species both economically and ecologically - are at historic lows. Striped bass are at record highs after being on the verge of collapse a little more than a decade ago. Shad and herring populations, though recovering, are only a fraction of their historic levels.
"I don't think anybody believes we'll get back to the abundances of Captain John Smith's era," said Goldsborough, of the Bay Foundation. "But I do think it is feasible to get to the ecosystem balance of that era. And with balance comes more stability than you would otherwise have."