During a fishing trip out on the Chesapeake Bay not long ago, as the sun set and seagulls circled, my friend hauled in a striped bass as long as my arm. We immediately recognized there was something wrong with the fish, however. It had lesions on its side.
Striped bass are the most popular saltwater sportfish on the East Coast. But there are millions like the one I saw that evening: with open sores and masses of gray nodules in their spleens. Both are signs of a chronic wasting disease called mycobacteriosis.
“In the Chesapeake Bay here, it is extremely common,” said Dr. Wolfgang K. Vogelbein, Professor of Marine Science at the Virginia Institute of Marine Science (VIMS). “Some of our data over the last 10 years suggests that the 2 to 3 year old fish -– the schooling, resident striped bass -– are showing the disease in epidemic proportions. Over 90 percent of those animals are infected.”
During his decade and a half of research, Dr. Vogelbein and his associates have made progress in solving some of the mysteries of “myco.” For example, he and his colleagues have concluded the disease is increasing the natural (non-fishing) death rate of striped bass by 15 to 20 percent per year.
Dr. Vogelbein said it’s clear that eating infected fish poses no threat to humans when the fish is cooked. However, handling stripers with open sores can pose a potential risk of infection to fishermen who have open cuts on their hands.
But Dr. Vogelbein’s important research is about to run out of federal funding before important questions can be answered -- in part, because of budget cuts in Washington DC.
“These are long-term expensive research efforts, at a time when funding for scientific research is declining,” he said. “We built this phenomenal laboratory here at VIMS. But now we’re out of money, or almost out of money. And we’re not going to be able to do the studies that need to be done unless we can get more funding for this work.”
One big puzzle has been the impact of myco on striped bass populations. If myco really is a deadly disease in striped bass, and the vast majority of the fish have it -- why are striped bass still so abundant?
Once overfished, striper populations hit a low of 8 million in 1982, according to the Atlantic States Marine Fisheries Commission (ASMFC). Then striped bass recovered because of bans on catching them in the late 1980s, which caused numbers of the fish to multiply more than eight fold, to 67 million in 2004. Since then, however, populations have declined by 26 percent, to about 42 million fish today, according to ASMFC numbers.
Vogelbein concluded that, while the moratorium helped to end the overfishing problem, the disease is increasing the mortality rate of the older fish.
“Just recently we necropsied a fish… that had a spleen almost the size of a football, and it was a solid granulomatous inflammation,” Dr. Vogelbein said. “So they can become incredibly nasty.”
But where does the disease come from? That’s an even bigger mystery. Dr. Vogelbein and other scientists have found myco almost everywhere they looked in the water and sediment –- and even in other species of fish. A variety of myco was even reported in Carp back in 1897.
This led Vogelbein to a theory. Mycobacteria have been in the environment for a long time. But myco is only causing disease at epidemic levels recently in the Chesapeake Bay because pollution, low oxygen levels, and poor food supplies are weakening their immune system, Dr. Vogelbein said.
Striped bass eat small, oily fish called menhaden, which have been overfished by industrial fleets out of Virginia. So maybe protecting menhaden would reduce the disease. But this, also, is uncertain.
“We’ve actually looked at menhaden, and it turns out that menhaden harbor a tremendous number of these bacteria in their tissues. Yet they don’t develop the disease,” Vogelbein said.
“And so there is this thought that maybe these animals could be the vectors of the infection to the striped bass. Because we really don’t even know how the striped bass get infected.”
This is perhaps a key question for the future of two the East Coast’s most important fish species: striped bass and menhaden. And yet, budget cuts in federal agencies that pay for scientific research could cut off Dr. Vogelbein’s important work before he and his colleagues can answer these questions.
That that is a symptom of a disease disturbingly common in humans: shortsightedness in failing to support scientists.
By Tom Pelton
Chesapeake Bay Foundation
(Photo of infected striped bass at top from VIMS)