After management efforts in the last decade rescued the striped bass stock from the brink of collapse, some are now suggesting the recovered stocks have outgrown their food supply and available habitat.
Right now, there is nothing but circumstantial evidence to suggest that is the case. But some scientists and fishermen say the large number of striped bass in the Bay is stressing the population, possibly resulting in the sores seen on a large number of fish last fall.
Maryland Department of Natural Resources' surveys found that about 12 percent of the adult striped bass caught during routine fall surveys had lesions, an unusually high number.
The root cause could be stress caused by so many fish. The current rockfish population is the highest the Bay has seen in decades. It is also made up of larger, and older, fish - which are more susceptible to stress than younger ones - than were found in the Chesapeake in past years.
Now, some scientists suggest, there may be so many fish in the Bay that they could be having trouble finding enough food. Or, it's possible that poor habitat conditions in much of the Bay are squeezing large numbers of fish into areas with only marginal habitat. Either case could stress the fish, making them vulnerable to infection. It's also possible that a disease could be spreading throughout the crowded population.
"All we've got is speculation right now," said Jim Uphoff, a DNR biologist who has studied rockfish for years. "The hope is that several months from now to either eliminate some things, or keep them in as part of a hypothesis."
A research proposal for a more detailed study may be finalized by the DNR as early as January, and scientists hope to begin examining the contents of the fishes' stomachs this winter to find out what they are eating.
Speculation about a food web out-of-whack has risen because the sores are only seen in adult striped bass - one of the major predator fish in the Bay. "I think there's been a huge surge in interest," Uphoff said.
While the number of striped bass have grown, spawning data show that reproduction of menhaden and bay anchovy - two of the main food sources of striped bass - have fallen in recent years. Menhaden reproduction has fallen to a level that will trigger a review by the Atlantic States Marine Fisheries Com-mission, a compact of East Coast states that manages migratory fish species.
"It's cause for concern, at least to keep an eye on it," said Joseph Desfosse, fishery management plan coordinator with the ASMFC. But he said the review does not necessarily mean anything will change, because a variety of other factors can influence menhaden abundance. Bay Program monitoring data also shows that populations of zooplankton, the required food of menhaden larvae and of all stages of other "forage" fish are declining in the Chesapeake, raising he possibility that the food chain in the Chesapeake is being altered.
"There's a lot of evidence for that," said Claire Buchanan, a biologist with the Interstate Commission on the Potomac River Basin, who chairs the Bay Program's Living Resources Monitoring Workgroup. "Something really big seems to be happening in the middle and lower Bay."
Jim Price, president of the Chesapeake Bay Acid Rain Foundation, said that of 13 striped bass caught in the mid-Bay in November - all between 18 and 22 inches in size - nine had no body fat. Stomach contents included clam, chum and sand shrimp, but no sign of menhaden, he said.
Research has shown that striped bass typically consume menhaden in the fall, an oily fish that helps the rockfish build up their fat reserves for the winter.
"The dramatic decline of the Chesapeake Bay's two most abundant and important species of forage fish, the bay anchovy and the Atlantic menhaden, are threatening the health of the Bay's striped bass population," Price said. "Possibly, the ecology of the entire Chesapeake Bay will be affected by the reduced numbers of these two important sources of food for the Bay's finfish population."
Bill Goldsborough, a fisheries scientist with the Chesapeake Bay Foundation, said the idea that poor nutrition could be contributing to the lesions was a "viable hypothesis."
"I tend to think there is something there," he said, "but I don't think we have enough information to say definitively what is going on." Goldsborough said that since the early 1980s - when striped bass were on the verge of a coastwide collapse - the species has been managed more conservatively than other fish.
The difference in management between a predator species such as the striped bass and the fish that it preys on could have created a food web imbalance, Goldsborough said. That doesn't necessarily mean that more striped bass should be harvested, he added, but rather that coastal states should "attempt to manage all species with the same level" of conservatism.
Exactly how serious the rockfish issue is is unclear. After all, while an unusually large amount of the striped bass population has ugly sores, there is a huge number of fish in the Bay that can be caught.
"It's not a good thing because [the sores] upset people," Uphoff said. "But what type of an omen it is, I don't know. We don't know if this is an epidemic that is going to get worse, or if this is as bad as it's going to get."
Goldsborough said the high population of rockfish is an "unusual situation" because of a series of abnormally high spawns, and that any overcrowding problems could diminish as the population in the Bay returns to normal levels over time.
Still, he said, the sores "allow us to see graphically that the habitat does continue to be sub-optimal and can't support the big level of production that we are capable of."