Our analysis of production and cost begins with a period economists call the short. run. Theshort run in this microeconomic context is a planning period over which the. managers of a firm must consider one or more of their factors of production as fixed.
Sharks have two sets of paired fins on the sides of their body, in the same general position as the main wings and horizontal tail wings of a plane. The shark can position these fins at different angles, changing the path of the water moving around them.
Fins are either single along the centerline of the fish: the dorsal fin, anal fin, and tail fin; or paired fins: the pectoral fins and pelvic fins. Pectoral fins help fish balance. The back fin or dorsal fin is also used in balance and protection and in some fish families (pike and gar) it is used for propulsion.