Goldfish have at least 7 fins, and each of them is there for a reason. So what does each fin, or pair of fins do to help goldfish swim?

The Names of the Fins

a. Pectoral

b. Pelvic

c. Anal

d. Caudal

e. Dorsal

Stability

Goldfish move in 3 dimensions, therefore have 3 directions they need to maintain stability in.

Firstly, imagine a model goldfish with a rod running through it from the mouth to the tail, with the model spinning around the rod. Goldfish use their anal, caudal and dorsal fins to prevent this movement.

Secondly, imagine the rod is running through the model from top to bottom i.e. from the dorsal fin to between the pelvic fins. The movement on this axis is also controlled using the anal, caudal and dorsal fins.

Finally, imagine the rod is going through the model from side to side, producing movement that makes the head and tail go up and down. Goldfish use their pectoral and pelvic fins to control this movement.

Direction & Steering

Goldfish move their caudal fin from side to side for forward propulsion. The pectoral fins are used for more delicate movement, both forwards and backwards.

Goldfish steer with their pectoral fins, and also use the dorsal fin when turning sharply.

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