Fish Diseases
- Is it safe to eat fish with small black, yellow or white bumps or worms in them?
- What is Largemouth Bass Virus and has it been found in Indiana?
- What is the yellow perch parasite (Heterosporis sp.) and has it been found in Indiana?
Is it safe to eat fish with small black, yellow or white bumps or worms in them?
Most reports of small black, yellow or white bumps in the fins and flesh of fish are the commonly observed parasites tapeworms, yellow grubs, white grubs, and black spot. While the appearance may be unappetizing, fish that is properly cleaned and cooked cannot transmit any parasite or disease to people who eat the fish. With proper kitchen hygiene and thorough cooking, fish parasites are not known to cause problems in humans. Like other meats, properly cleaned and cooked fish can still transmit the basic food poisoning diseases if left out or handled improperly after cooking. Worms or grubs in fish go through a complex life cycle and undergo physical changes within a variety of organisms called hosts. Most fish have parasites and they seldom affect the health of the fish except under unusual conditions. Most fish parasites have complex life cycles often involving birds, snails, and microscopic animals. Attempts to control them are usually futile and unnecessary except in controlled hatchery or fish farming situations. Larval tapeworms are common in the organs and body cavity of many fishes. Because internal organs are discarded when fish are cleaned, this parasite is often overlooked. Tapeworms resemble long thin ribbons about 1/16 of an inch wide. Black spot is caused by a parasite called a fluke which burrows into the skin of fish. The black pigment (about the size of a pin head) forms in the tissue surrounding the fluke and is a reaction of the fish to the parasite. The fluke itself is actually a white color. Yellow grub is caused by flukes which burrow into a fish and curl up into a sac under the skin, in the muscle or in internal organs. These flukes are often found near the dorsal fins, but occasionally in the organs. When freed from the sac, flukes may be up to one half inch long. White grubs are a fluke that penetrates the skin and forms a sac in the kidneys or liver. These grubs are similar to but smaller than yellow grubs.
What is Largemouth Bass Virus and has it been found in Indiana?
Largemouth Bass Virus (LMBV) is one of more than 100 naturally occurring viruses that affect fish and is closely related to viruses found in frogs and other amphibians. Its origin and how it is spread are not known. The virus appears to infect other species of fish, including smallmouth bass, bluegill and crappies, but has only been associated with death in largemouth bass. The virus was recently discovered following a die-off of bass in Lake George on the border of Michigan and Indiana near I-69. Previously, the virus had been found as far north as Missouri, Tennessee, and Kentucky. Fisheries managers in these states encourage anglers to help prevent the spread of this disease by following these general guidelines:
- Clean boats, trailers, and other fishing gear and draining live wells and bait buckets between fishing trips.
- Do not move any fish, live bait or fish parts from one water body to another.
- Schedule bass tournaments during cooler weather to reduce fish stress.
- Report dead or dying fish to the DNR.
Help educate other anglers in proper handling of live fish and bait.
What is the yellow perch parasite (Heterosporis sp.) and has it been found in Indiana?
The parasite Heterosporis sp. has been found primarily in yellow perch in the Eagle River Chain of Lakes in Wisconsin and Leech Lake in Minnesota. The parasite is also known from eels in Japan and Taiwan, in aquarium fish in France and Germany, and may also infect walleye. This microsporidian parasite does not affect people. The infection shows no visible signs on the outside of the fish. It causes the flesh to have a cooked or freezer burned appearance (white areas) of tissue inside the fish. The infected muscle cells reduce the quality and change the texture of the fillet. The parasite's life cycle is only partially known. As infected fish die and decompose, spores are released into the water and are swallowed by other fish. Muscles just behind the head seem to be infected first. The infection then spreads throughout the entire body. To assist in controlling this disease, report any suspected case to the nearest DNR office and keep the fish refrigerated until a biologist can inspect the tissue. In addition, practice the following precautions:
- Infected fish should not be thrown back into the lake; they should be placed in the garbage and taken to a landfill, burned or buried.
- Thoroughly dry all equipment and boat exteriors before using in other water bodies because the parasite spores may be present in lake water, but cannot survive drying.
- Drain all live wells and bilges. Because it is impossible to thoroughly dry these areas, disinfect with one cup of bleach in five gallons of water before moving to other water bodies.
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