Minimum Size
In fishing regulations, minimum size refers to the size limit that a fish must be or bigger if it is to be kept legally. The size limit is usually measured in length. For example, the minimum size for trout caught in the tidal waters of BC is 30cm, so all trout must be 30cm or longer if you decide to keep them.
The purpose of a minimum size is to ensure that juvenile fish are released so they have a chance to grow and produce more fish before being harvested at a later stage of their life.