In the very short period (market period), the time is insufficient for firms to adjust their output in response to a change in price. The quantity of the good available for sale is fixed. For example, the supply of fresh fish brought to the market for the day is fixed. Regardless of how high the price goes, no more fish can be made available on that day. This situation is represented by a vertical supply curve, which indicates that the quantity supplied does not change as the price changes. A vertical supply curve signifies perfectly inelastic supply (elasticity of supply is zero).