Q: We caught an 18-inch Atlantic cod in the Gulf of Maine in about 240 feet of water, 90 miles east of Gloucester, Massachusetts. It was covered with sores. We fished at one spot for several hours with a steady bite, yet this was the only fish that had these sores. We released the undersized fish, but even if it had been a 20-pounder, those sores were so disgusting that we would have thrown it back anyway. Can you tell me anything about the sores?

Dave Barrett
Tyngsboro, Massachusetts

A: Unfortunately, fishes are susceptible to a variety of ailments including skin ulcers, fin-rot and lesions. These may be caused by any of several different factors including biological (bacterial, viral, parasitic, fungal); environmental (pollutants, natural toxins, poor water quality); or even natural physical changes (such as sudden temperature change or trauma). These symptoms might occur naturally in a few fishes, but biologists become concerned when more widespread outbreaks affect whole populations, sometimes resulting in mass mortalities. A pathologist would have to determine exactly what was responsible for the ulcers observed on your sample. Next time, you might consult a public health agency or local university, preferably with specimen in hand. — Mike Fahay