How to measure a fish for the rules
Most states measure freshwater fish by total length: mouth closed, fish flat, tail lobes squeezed together, from the tip of the snout to the tip of the tail. Some saltwater species are measured by fork length, to the fork of the tail. CatchVault records whether each length came from LiDAR, an AI estimate or a manual measurement.
Total length, step by step
- Lay the fish flat on its side on a measuring board or ruler.
- Close the mouth and push the snout against the zero end.
- Squeeze the tail lobes together and read the longest point.
- Measure in a straight line, not along the curve of the body.
When fork length is used
Fork length runs from the snout to the center fork of the tail. Several states use it for certain saltwater species, and federal rules use it for some offshore fish. The rule book says which method applies to which species.
Using a phone to measure
A phone measurement is fast and good for records. CatchVault uses the LiDAR sensor on supported iPhones and an AI estimate on others, and tags each catch with the method. For a fish right on the line, use a physical board the way your state defines it.
Questions & answers
Do you pinch the tail when measuring a fish?
In most states, yes, for total length. Check your state’s definition, since a few measure with the tail in its natural position.
Sources for this entry
- CatchVault state regulations: Company-published summaries for 48 states, each linked to the agency.
- CatchVault on the App Store: The developer’s listing: features, price and supported devices.
Practical guidance is original editorial writing. App details come from the developer’s published descriptions, checked .
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How the related websites connect
This reference is published alongside CatchVault. State-by-state summaries and license guides live on the CatchVault website, and sister references cover fish identification and fishing apps in general.
Explore related references · CatchVault’s official websiteCite this entry
Best Fishing Regulations App. “How to measure a fish for the rules.” Content reviewed .
https://bestfishingregulationsapp.com/how-to-measure-a-fish-legally/