Ask Outdoors Girl

August 09, 2009|By Candus Thomson

Barry Marseglia of Solomons writes: "I've been catching rockfish in the mid-bay region with red sores and red rashes all over the skin. These sores have an odor. Also, in the Calvert Cliffs area, I've caught rockfish with a yellow tint. ... If there is a problem on the skin of the fish, it seems to me it's also in the cells or the flesh of the fish."

Mark Matsche, a fish health biologist at the Cooperative Oxford Lab, replies: "Some striped bass in the Chesapeake Bay have a bacterial disease called Mycobacteriosis. This also occurs to a lesser extent in striped bass in the Atlantic Ocean. The bacteria target the spleen of the fish initially and then often progresses in severity over a period of one to two years resulting in skin lesions ... loss of weight and other types of lesions. Unlike most fish diseases, Mycobacteriosis is persistent in the population (since at least the 1970s), and because the disease debilitates the fish, they are susceptible to other opportunistic skin infections. Mycobacterial lesions do not have an odor associated with them, but other types of bacterial infections do. Because it takes more than a year for Mycobacterial infections to spread on a fish, it is not uncommon to find other types of bacteria in the skin lesions (and in internal organs), and those bacteria may give off an odor.

"There can be a number of causes for "yellow coloration" on fish, which is increased pigment (melanin) formation on the skin. Fish with Mycobacteriosis often accumulate melanin in or near lesions, but without seeing those fish we cannot make any determinations. Mycobacteriosis has been documented in numerous fish species."

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