Fish Measurements: Total Length and Girth

All freshwater Florida Fish and Wildlife Conservation Commission regulations and the "Big Catch" program depend on "total length." The total length is the maximum length of the fish, with the mouth closed and the tail fin pinched together. The best way to obtain this length is to push the fish's snout up against a vertical surface with the mouth closed and the fish laying along a tape measure, then pinch the tail fin closed and determine the total length. Do NOT pull a flexible tape measure along the curve of the fish. The photo to the right shows a bass on a measuring board with the mouth held shut. Prior to getting a final measurement the caudal (tail) fin will be pinched shut.

TOTAL LENGTH MEASUREMENT
Animation of measuring total length, by Bob Wattendorf
"Girth" is best measured with a fabric ruler, such as tailors use. It can also be determined by drawing a string around the fish at its widest point marking where the string overlaps and then measuring the distance between the overlapping points on a conventional ruler. The measurement should be taken perpendicular to the length of the fish. This measurement is analogous to measuring the circumference of someone's waist. Knowing the girth is important when trying to certify a fish for a record, and provides useful information to biologists about the relative condition of a fish.

GIRTH MEASUREMENT
Animation showing measuring girth, by Bob Wattendorf

Using total length and girth you can get a rough estimate of a fish's weight using various formulas. Please remember that if you are going to release your catch, it is very important the fish be properly handled and released as quickly as possible. See here for live-release guidelines. Also don't forget if you catch a quality-sized fish that you can receive a free angler-recognition certificate and sticker from the "Big Catch" program.

(Note: Marine [saltwater] fishes are sometimes measured using other techniques that are also used by freshwater fisheries scientists. Click here to see other ways of measuring fish)

Take Me Fishing.org is a great general information site for recreational anglers and boaters.

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