NANFA-- catfish trematodes

Jay DeLong (
Sun, 18 Jun 2000 11:28:15 -0700

> A few questions about this:
> 1] How does the trematode get to the catfish? Via eating the
> snail, eating snail
> droppings, or the parasite leave the snail and actively get into
> the catfish?

Some trematodes have an immature phase which emerges from the snail, which
then attaches to, or is passively taken up by, the fish host. They form
cysts in the tissues of the fish, the fish is eaten by birds, and the
trematodes mature there, producing eggs which are released in the bird's
feces and the eggs are ingested by snails.

> If
> the black carp eat snail with parasite won't it be infected or
> become the host and become inedible?

Edibility of the carp isn't a concern. If the carp isn't eaten by a bird
the cycle ends.

> 2] Aren't there other NA fishes [bullheads, buffalos, suckers,
> perches, etc.] or
> turtles or birds that can eat snail? Isn't reducing the number
> of small snail enough to reduce the parasite problem?

I imagine using a known (or potential) piscivore to control the snails is
not an option to the catfish growers. Also, I kinda think there aren't any
other effective snail-eating fish species.

I think we're just going to have to spend more money at the grocery for our
catfish and insist that growers find better ways to run their operations,
such as covering their ponds with netting to keep the pelicans out.

Jay DeLong
Olympia, WA

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