The fins are composed of bony spines protruding from the body with skin covering them and joining them together. Fins are used for movement, stability, nest-building, spawning, and as organs of touch. They can be single or paired. The caudal or tail fin is used for propulsion. Fish that have forked caudal fins usually are fast swimmers. The anal fin stabilizes the fish and provides propulasion while it is swimming. Ventral fins are also used to provide stability in swimming. The paired pectoral fins are used for manoeuvering the fish. The single dorsal fin helps balance the fish while swimming and also during sudden movements or turns. The rays of this fin are often sharp, and a spine is often present.

Image credit: Marine Education Society of Australasia

pectoral fin: one of a pair of fins located on either side of a fish behind the gills used for balancing and braking.

The main purpose of the dorsal fin is to stabilize the animal against rolling and to assist in sudden turns. Some species have further adapted their dorsal fins to other uses. The sunfish uses the dorsal fin (and the anal fin) for propulsion.

so I think it should be pectoral fin