A slot limit is a tool used by fisheries managers to regulate the size of fish that can legally be harvested from particular bodies of water. Usually set by state fish and game departments, the protected slot limit prohibits the harvest of fish where the lengths, measured from the snout to the end of the tail, fall within the protected interval.[1] For example, on a body of water where there is a protected slot limit on largemouth bass between 12 and 16 inches (30 and 41 cm), largemouth between those lengths may not be harvested.[2] In this example largemouth bass shorter than 12 inches (30 cm) and longer than 16 inches (41 cm) may be removed from the water and kept for personal use in accordance with local fishing regulations.
https://en.wikipedia.org/wiki/Slot_limit