Just in time for Halloween, a troubling new study suggests that the Chesapeake Bay's rockfish may, in fact, be dying from the bacterial disease that now infects more than half of them.

Researchers from the Virginia Institute of Marine Science, Coastal Carolina University and the U.S. Geological Survey concluded that mycobacteriosis, the chronic disease that has been inflicting awful-looking lesions on our state fish since 1997, has been claiming a previously unknown share of them.

It's particularly troubling news since the bay is the main breeding and nursery ground for all the striped bass that range along the Atlantic coast.  Stripers, better known in these parts as rockfish, are a major commercial fishery in the bay, and a prime catch among recreational anglers coastwide.

Because rockfish don't travel in schools, their deaths aren't as easily noticed as when, say, a mess of menhaden get trapped in an oxygen-deprived cove and go belly-up.  But scientists analyzing fish sampling data have noticed an uptick in mortality among rockfish in Maryland waters since 1999 that couldn't be attributed to them being caught. 

It wasn't clear at first whether the deaths were from disease or natural causes, until researchers factored in the results of a three-year study of the bacterial disease in rockfish.  They then found that fish with the lesions were 30 percent less likely to survive another year, that older females were more likely to succumb than males, and that the die-off increases in summer, when the fish may be more stressed because warmer temperatures have reduce oxygen levels in the water.

For more on the study, look here.  The photo from VIMS below is of a 20-inch rockfish mottled with lesions.