Striped bass with strange, ugly sores are being spotted around the Chesapeake Bay, and scientists are planning to step up research in coming months to learn what is ailing the fish. While sores have been reported on adult striped bass for several years, biologists say more fish appear to be affected this year. The sores tend to be found on larger fish - usually 16 inches or larger in size - and the affected fish appear to have little body fat. "The fish are in trouble," said Jim Price, a former charter boat captain who has caught dozens of fish with sores in the Choptank River and nearby areas of the Chesapeake Bay. "Other fisherman that I've talked to have caught them up and down the whole Bay. It's not an isolated area. It's a Baywide problem."
Fish pathologists say the sores on striped bass are not caused by pfiesteria. The sores are generally found on different parts of the fish than pfiesteria lesions, and have shown up on fish throughout the Bay, unlike pfiesteria, which has been confined to a few areas. "They have none of the earmarks of the pfiesteria problem," said Steve Jordan, director of the Cooperative Oxford Laboratory - run by the Maryland Department of Natural Resources and the National Marine Fisheries Service - which has examined a number of the fish. Wolfgang Vogelbein, a fish pathologist at the Virginia Institute of Marine Science who examined more than half a dozen infected striped bass in mid-October said his preliminary diagnosis was that the sores were caused by Mycobacterium, a naturally occurring pathogen in the Bay.
Mycobacterium may also pose a health risk to people who handle infected fish if an open wound comes into contact with infected parts of the fish, though infections in people are relatively uncommon. In humans, the infection is known as "aquarium handlers disease" or "fisherman's handlers disease," and may result in lesions forming on the person's skin.
"The fish that we are seeing can have lesions all over the body and can have shallow ulcers associated with this condition as well," Vogelbein said.
What is unusual, he added, is that Mycobacterium is typically a slow-growing infection that can affect fish for long periods of time with no external symptoms other than emaciation.
"Never have I seen these types of skin ulcers and sores associated with that infection," Vogelbein said, "and fishermen might easily be misled into attributing this condition to pfiesteria." He cautioned that "our studies are not anywhere near complete on this" and that he had not compared his findings with Maryland scientists. Maryland fisheries officials say they have seen striped bass with sores since 1994, and that the lesions had been infected with a variety of bacteria - something that is not unusual for any open wound on a fish.
While Mycobacterium was seen in some of the fish this year, it was not identified in previous years, said Eric May, a fish pathologist at the Oxford lab.
As a result, May said, it is unclear whether Mycobacterium is what caused the illnesses, or whether other stresses are weakening the fish and allowing more to become infected. "More work needs to be done to sort that out," he said.
The lab, along with the U.S. Fish & Wildlife Service and other agencies are planning an intensive research effort into the problem. Jordan said most of the sick fish were skinny and in "terrible nutritional condition."
"Until we do some more work on it, it's a chicken and egg thing," he said.
"Maybe they're in poor condition because they have infections, or maybe they have infections because they're in poor condition." Jordan said scientists at the lab are working on the hypothesis that the fish are stressed from malnutrition and are therefore more susceptible to infection. That could mean there are a lot of striped bass in the Bay, and too few "forage" fish for them to feed on, Jordan said.
Price said the fish may also be stressed by poor water quality in parts of the Bay. Low dissolved oxygen levels prevent the fish from using deeper areas, forcing them to stay closer to the surface where temperatures are often too warm for the fish during the summer.
"There are schools in the Bay that seem to be healthier than other schools," said Price, president of the research-oriented Chesapeake Bay Acid Rain Foundation, who has been collecting striped bass for the DNR and and other agencies to analyze.
Maryland surveys of adult fish have found about 5 percent are afflicted, Jordan said.
Price said even more fish may be affected. "Around 12 percent of the fish that I've seen in the Choptank have been affected, and the last one was in terrible condition, it was the worst one that I've seen all year," Price said. "If you saw this fish, you wouldn't even want to take it off the hook. you would want to cut the hook off with a pair of scissors."
Price said that 13 of 111 fish taken in the Choptank River between Aug. 18 and 23 had sores. Between Oct. 2 and 14, he caught 42 fish in the Choptank, of which six had sores, and 16 in the Bay, of which two were sick.
Both Price and Jordan said that although the fish look to be in bad shape, they are hardy enough to pursue prey and fight vigorously when hooked on a line.
"Obviously, they are capable of eating and striking at things," Jordan said.
As with any fish found with lesions, he said the fish should not be handled or eaten.
Fish with sores can be reported to the Maryland Fish Health Hotline 1-888-448-0012.
In Virginia, they may be reported, or brought to the Virginia Institute of Marine Science, Aquatic Animal Disease Diagnostic Center, 1-804-642-7249.