Tapioca like growth identified as larval trematode parasites (digenean metacercariae).
Observation: This is the first time we have seen these around a Sheefish heart. Some people say these are similar to "cottage cheese crab" but it's the first time we have seen it in fish.
LEO says: Sheefish is also commonly referred to as "Inconnu," and can grow to be about 42 inches (1 meter) in length. They can live 30 years or more. Juvenile sheefish eat insects. Adults feed almost exclusively on other fish. Sheefish, migrate long-distances, as far as up to a 1,000 miles (1,600 kilometers) within a single summer. Sheefish found in the major Alaskan river drainages such as the Kuskokwim, Yukon, Selawik, and Kobuk rivers typically overwinter in the brackish waters of the bays. During spring break up, many they travel upriver to feed. Some will migrate upriver later in the summer to spawn. Some "resident" sheefish do not migrate. Instead, they remain in freshwater their entire lives.
Resource:
Alaska Department of Fish & Game Consult: Jayde Ferguson, Fish Pathologist writes, "We received this sample late last week. These parasites appear to be digenean metacercariae (larval trematodes). They are not at all related to the “cottage cheese crab” disease, which is caused by microsporidians (protozoan-like). Digenean metacercariae is a term used to describe a type of larval trematode. It’s a general term. There are actually a few examples listed in the book: Black spot disease (Neascus) and Diplostomulum." Dr. Ferguson continues, "There are also others in our shellfish book. I think the following are the main points:
- The parasite was a larval trematode (flatworm), which are common in wild fishes.
- It appears to possibly be an undescribed species, although this field of work with sheefish is greatly understudied.
- The parasite was not at all related to the “cottage cheese crab” disease.
- Follow FDA guidelines to kill parasites in fish prior to consumption (cook to internal temp. of 140°F or freeze at -4°F or below for 7 days)."
For more information on diseases in fish, see link
