Mike Matsche, a fisheries biologist with the Maryland Department of Natural Resources, remembers a day in 1998 when the calls started coming in. Fishermen were finding some of their catch covered in lesions that looked like cigarettes had been snuffed out on their scales. The sores were showing up on one type of fish in particular: the bay’s famed striped bass, known as rockfish.
Matsche and others soon found that about a quarter of bay rockfish had mycobacteriosis, commonly known as “fish tuberculosis.” The affliction is a slow, wasting disease that shrivels a fish’s internal organs and muscle tissue and, in some cases, results in outward lesions.
Seven years after first being discovered in the bay, mycobacteriosis has now spread to nearly 70 percent of the resident striped bass population, with 20 percent exhibiting the disease’s most distinct calling card: the sickly, open sores on the exterior of the fish.
“Most of the fish that get the disease will die,” said Wolfgang Vogelbein, a scientist with the Virginia Institute of Marine Science.
Experts studying the epidemic believe a polluted and possibly over-fished ecosystem in the bay is breaking fish immune systems, leaving rockfish vulnerable to deadly bacterial infection. Mortality rates among adult rockfish have surged 20 percent since the disease was first detected.
The Chesapeake Bay’s current plight appears to be a microcosm of a perfect storm taxing rivers and bays across the country. This phenomenon, highlighted in our January 18, 2006 web story, A Rash of Mysterious Fish Kills, and by National Public Radio, is the likely cause of dozens of fish die offs up and down the east coast. In places like the Shenandoah and Susquehanna Rivers, millions of lesioned fish died in fish kill events last summer. Scientists can find no single culprit and believe that these rivers, like the Chesapeake Bay, are becoming toxic to aquatic species and making fish susceptible to disease.
The bay epidemic has not received much public attention or research funding, likely because the fish tuberculosis does not produce a one-time die-off of millions of rockfish. Kills that leave a sea of dead fish in a matter of hours tend to garner more attention, as was the case with several die offs in the bay’s tributaries last summer. “We may never see an acute die-off with millions of dead floating fish, but rather a continuous and steady die-off that will go unnoticed at the local level,” Vogelbein said.
The fact that the die-off is slow makes proving that the disease is responsible for a surge in rockfish mortality more difficult. Absent extensive monitoring and tagging of fish, it’s hard for scientists to determine why natural fish mortality (fish deaths aside from commercial and recreational fishing) is up among rockfish. Some point to over-fishing of Atlantic menhaden, a primary food source of rockfish. Scientists like Vogelbein say poor diet is likely just one reason that the disease is spreading and more fish are dying. Fully explaining the die offs, scientists say, will take more time, and a lot more money.
“Striped Bass are not happy in the Chesapeake Bay in the summer,” Vogelbein said. Their distress is the result of a variety of plagues. Nutrients dumped into the bay are the main bad actor at play, according to Vogelbein. This includes everything from agricultural and animal runoff to lawn fertilizer. “We all want to live on the bay; we all want to live on the water. We all want green lawns,” Vogelbein said. “We are the cause [of the fish illnesses].”
The bay’s notorious “dead zones” are likely making matters much worse. These areas have too little oxygen in the water to sustain fish, diminishing refuge habitats and forcing fish to crowd in certain pockets of the bay where pollutants accumulate. While dead zones have existed in the Bay for years, they have expanded across much of the bay, likely exacerbated by unusually warm summer water temperatures. Combined with a host of other stressors present in the bay, this lack of oxygen is likely making rockfish more susceptible to opportunistic pathogens like mycobacterium, which wouldn’t normally affect a healthy fish.
James Price, a long-time bay fisherman and president of the Chesapeake Bay Ecological Foundation, expressed frustration that state officials and fisheries managers have not given the epidemic greater attention. “Nobody is trying to put together a big picture,” Price said. “Each state is looking at their own problems.”
Price notes the danger in not collaborating on a solution in the bay could be disastrous for the entire Atlantic region. “Every [Atlantic] state that has an active fishery or recreational fishery is relying on the Chesapeake Bay as a nursery ground,” Price said.
Trouble with bay rockfish struck a nerve with federal officials and fishermen alike: The rockfish had suffered a disastrous population crash in the 1980s and their rehabilitation over the last two decades has been the oft-cited (and seemingly solitary) success story to come out of the Chesapeake Bay in recent years.
Part of the reluctance to highlight the problem is likely fueled by state-economic interests, according to Derek Orner, a scientist with the National Oceanographic and Atmospheric Administration. Virginia boasts a substantial menhaden industry and is reluctant to blame the rockfish demise on over fishing of that stock, the rockfish’s favorite snack. Maryland, which derives great benefit from the bass fishery, doesn’t want to create unnecessary alarm about a disease that is still not well understood.
Charter-boat fishermen face the same dilemma: draw attention to the problem and you scare away your customers, ignore the problem and it gets worse until there is no catch left for the customers to fish.
The nation’s fishing industry is largely controlled by eight regional marine fisheries councils which manage each fish species, assess stock and control how many fish are caught. A recent report by the U.S. Commission on Ocean Policy, a presidential-appointed panel addressing ocean and coastal policies, recommended moving toward an “eco-system based” approach to managing waterways such as the bay. For scientists like Orner, looking at an aquatic habitat any other way doesn’t make sense. Fish do not live in isolation, Orner says: Rockfish levels depend on menhaden levels, which depend on weakfish levels, which control bluefish levels. Any major tilt in one species has a cascading effect on the rest.
For the moment, scientists are grim, but say more studies are needed. Vogelbein’s team is currently monitoring and tagging fish with the help of commercial and recreational fishermen in the bay. But there are still several unknowns. Fishermen are currently instructed to throw visibly sick or lesioned fish back into the bay, but some scientists fear such a system is stockpiling the epidemic in the bay, while harvesting healthier fish.
Meanwhile, funding for research into an epidemic affecting three-quarters of the bay’s greatest stock is surprisingly scarce. U.S. Geological Survey’s Vick Blazer, who has led a team of scientists studying mycobacteriosis, said there is no more funding for their research in the coming year, as dollars are being directed toward the bay’s more infamous plagues, such as nitrogen runoff. This has left scientists like Blazer, who see nitrogen as just one of several factors causing the perfect-storm epidemic, deeply frustrated.
In the back of everyone’s minds is the memory of a time when rockfish were almost a thing of the past, and the fear that they might someday reach that point again.
“It wasn’t too long ago that we had a major population crash,” remembers Ottinger. “We certainly don’t want to find ourselves there again.”
