Total length and fork length are different measurements

Use the method specified for the named species and applicable rule.

By Louisiana Deep Sea Fishing · 2 min read · Updated October 16, 2026

A fish’s measured length only helps when it is the measurement the rule requires. Total length, straight fork length and curved fork length do not describe the same path. Do not use a convenient tape reading from a photograph as a legal conclusion.

Recognize the terms

Total length runs to the tail’s extreme end using the prescribed positioning. Fork length ends at the tail’s fork. A straight measurement and one taken along the body’s curve can differ. Some specialized species measurements use other start/end points; consult the exact agency illustration.

Set up before keeping fish

Have the appropriate measuring equipment available and learn the required positioning, including any mouth or tail instructions. A marked board can simplify repeatable measurements, but markings must be suitable for the fish and measurement involved. A curved tape and a straight board are not interchangeable for every rule.

On a charter, ask the crew to demonstrate the measurement for expected targets. Keep fish handling, release needs and exposed hooks organized. Measuring is not a reason to delay appropriate release or attempt to control an unfamiliar large fish independently.

Match the result to the complete rule

Identify the fish, check the named size method, then read the minimum/maximum/slot and other conditions. Do not round a doubtful reading into compliance. The LDWF saltwater resource and freshwater resource link rule and measurement context; NOAA governs relevant federal fishery requirements.

Use the catch-rule checklist for the surrounding conditions. A measured fish can still be outside an open harvest period or exceed an applicable count.

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