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.
In the majority of fishes, however, there are one, two, or three dorsal fins, a distinct tail fin, and an anal fin. These are called median, or unpaired, fins. In addition to these unpaired fins, most fish also have paired fins.These are the pectoral fins, placed just back of the gills, and the pelvic, or ventral, fins, variable in position and sometimes lacking entirely.he paired fins may be anterior (pectoral) or posterior (pelvic). In some fishes, such as the Gadidae and Blenniformes, the pelvic fins are anterior to the pectoral fins. The skeleton of paired fins consists of cartilaginous or bony rays, which articulate to the skeleton of the girdles of the limbs.