How to measure a fish
Lay the fish flat, close the mouth, and measure in a straight line using the method the rule names. Total length and fork length are not interchangeable.
Use the definition on the rule
States do not share one measuring stick. Florida's Fish and Wildlife Conservation Commission says most saltwater finfish limits use either fork length or total length, and it tells you which motions are part of the measurement. South Carolina measures freshwater fish as total length, and some saltwater species as fork length. Atlantic billfish under NOAA use lower-jaw fork length, which starts at the lower jaw, not the tip of the snout.
If you fish more than one state, do not carry a single habit across the line. Open the rule for that species. Hankorama's Size Limits tool is a starting table with the agency link beside the note. Missing data is not "no limit."
Total length
On Florida's saltwater page, total length runs from the most forward point of the head, mouth closed, to the farthest tip of the tail with the tail compressed or squeezed, fish on its side. South Carolina's freshwater diagram is the same idea: snout to the tip of the pinched tail, filaments excluded.
Squeezing the tail is part of that definition in Florida. Leaving the tail spread, or measuring along the curve of the body, changes the number. FWC says a flexible tape along the curve is the wrong tool for these limits.
Fork length
Fork length stops at the center of the fork in the tail. Florida measures from the tip of the jaw or snout, mouth closed, to that fork. It is shorter than a pinched-tail total length on the same fish. A slot limit written in fork length fails if you report total length instead.
Lower-jaw fork length, used for Atlantic billfish on the NOAA recreational page, starts at the tip of the lower jaw and ends at the fork. Do not start that one at the bill tip.
On the boat or the bank
- Put the fish on a flat board or a rigid ruler, not a bent tape over the belly.
- Close the mouth. Start where the rule starts.
- End where the rule ends: pinched tail tip, or the fork, or the lower jaw to the fork.
- If it is short, or you are unsure, put it back. A release photo has its own rules. See how to photograph a fish you will release.
Regulations change, and seasons close. This page explains measurement methods cited by those agencies. It is not the regulation.
Questions that still come up
- Is a longer number always the legal one?
- No. Pinching the tail for total length makes a different number than stopping at the fork. Use the method named in the rule for that species and that water. A bigger number from the wrong method does not make the fish legal.
- Can Size Limits tell me if I can keep this fish?
- It can show a dated recreational size and bag note for a US state, with a link to the agency page. It is not a live regulation feed and it is not legal advice. Read the official page before you keep anything.