gold fish has a closed circulatory system..what does that mean?

Answer 1

This means that the heart and gills are linked by blood vessels in a circuit (a single circulatory circuit to be exact). This means the fluid/blood only passes in the circuit and doesnt sit and perculate in the tissues etc. This makes it a much faster and efficient process than an open crculatory system as the pressure does not decrease

Answer 2

It means the blood in the goldfish circulates in closed pipes like arteries and veins.