GREAT OUTDOORS: Viruses, disease can take toll on fish

During the spring, diseases seen in several species of fish command the attention of area anglers. While some lead to fish mortalities, others are merely a nuisance. Those that I have seen include viral hemorrhagic septicemia (VHS), lymphocystis, myopathy and saprolegnia. Over the weekend, I was tipped off by anglers heading to the lake that there were noticeable numbers of bluegills dead and dying in East Harbor and West Harbor. The Ohio Division Wildlife is investigating, as it takes multiple fresh specimens to confirm VHS, but the observed symptoms are consistent with the often-fatal disease. They include swimming in circles on the surface, a bloated stomach, bulging eyes, visible bloody veins on the head, open sores and bloody internal organs. VHS was first seen in the Great Lakes in 2005 when thousands of muskies died in Lake St. Clair and elsewhere. I recall seeing some trophy-size carcasses floating in the lake and washed up on island coastlines. In 2006, the virus killed thousands of fish, including yellow perch, freshwater drum (sheepshead), gizzard shad, round gobies, walleyes and others. This outbreak prompted the U.S.Department of Agriculture, Animal and Plant Disease Inspection Service to ban interstate shipments of emerald shiners, causing shortages of the prized bait during perch season. It has been relatively quiet most years since, except for noticeable flareups in 2011 and 2017. The virus is active when water temperatures range from 39 to 54 degrees. Peak mortality occurs at 39-41 degrees, but deaths rarely occur after water temperatures reach 59. On board of Capt. Mark Cahlik's boat while filming an episode of MidWest Outdoors TV earlier this month, some walleyes had red lumps growing on their skin. I was filmed explaining that these sores are lymphocystis, a skin virus that is commonly seen this time of the year. Sometimes called fish warts, it spreads in the winter and spring when fish are crowded and rubbing against each other during spawning activities. Unless a fish develops a severe infection that spreads to internal organs, it is rarely deadly. The virus does not usually penetrate into the meat, and unaffected fillets are perfectly safe to eat. A rarer but more serious condition that has occasionally been seen locally is walleye myopathy. Affected fish look normal on the outside but the fillets look freezer-burned or grainy (sandy flesh) and should not be eaten. Saprolegnia is a condition that is often seen when fish are overcrowded or handled by anglers and have their protective slime layer removed. It peaks when water temperatures are around 59 degrees but can be present with temps from 32 to 95. This "water mold" starts as cottony white patches that can turn brown with age. It is commonly seen on the lower jaws of smallmouth and largemouth bass where anglers have been gripping them for pictures after landing them in the spring. I have also seen dead bass with a fuzzy brown hand print across the side of their body where they were held by anglers who likely failed to wet their hands before posing for a picture, causing the loss of the protective slime layer. Wetting one's hands before handling fish makes a big difference in successfully releasing those that will survive long-term. Bass spend a lot of energy during spawning season, especially the males that constantly guard their nests from gobies and other egg predators. The added handling stress is sometimes the nail in the coffin for these already frazzled fish. While it does not run rampant in the wild fish population overall, saprolegnia can grow into a serious problem when it flares up in fish hatcheries where fish are crowded in raceways and rearing tanks. Quick treatment can minimize mortalities there, but that is impractical in the wild. Most local fish have parasites in them too, but that is a whole other story.