Neascus (Black spot disease)

Cause of disease:

Parasite - Uvulifer spp., Neascus spp., Black grub

What does it look like?

These parasites are small and produce black pigmentation that resembles black pepper sprinkled on fins or flesh (fillets) of fish.


Fish species affected:

All species of fish in Minnesota lakes and rivers are susceptible. Fish that inhabit shallow areas are most affected.

Life cycle:

Eggs are released by fish-eating birds into the water. Eggs develop into intermediate stages of the parasite in snails. These free-swimming parasites penetrate the muscles of fish and encyst. Black pigmentation is deposited onto these cysts. Infected fish are consumed by birds where the life cycle starts all over again. Adult worms are seen in fish-eating birds.

Where is the disease is found?

Very common throughout Minnesota.

Is it safe to eat?

Yes, although unsightly, the fillet is safe to eat if it is well cooked. Always cook fish well before consuming.

How can I prevent the spread?

There are no practical means to control this parasite.

Disposal of unused portions:

Unused or uneaten portions of fish should be buried or disposed of with household waste. Fish entrails should never be discarded back into the lake.

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