How Do I Estimate the Size of my Billfish?

Estimating the weight of the fish or by measuring the fish when it is in, or alongside the boat or in the boat.

If the fish is up to 3 Ft. in length it may be carefully brought on board and measured using a standard measuring tape.

However, large fish should remain in the water. If you estimate the size of the fish, especially the weight, get a consensus from the entire crew immediately after release, and record immediately.

For measuring length of fish in the water, it is best to rig up a simple tape measure. It helps if it is flexible, and at least 10 Ft. long. A great method is to attach a tennis ball (or similar) to the zero end and when a fish is alongside, or being held at the back of the boat, float the tennis ball to the tail fork and get a measurement to the fish’s snout, or to the tip of the lower jaw for billfish. For billfish, it is important that the recorded measurement should state where the fish was measured from and to (i.e. lower jaw to tail fork length or total length – tip of bill to end of tail.

Giving both the length and the weight for every tag and release will allow the recording of the most complete information and result in the best comparison should the fish be recaptured or the data used in a scientific analysis.

How to Measure the Fish

An accurate measurement is very useful to both anglers and scientists. When measuring a fish, there are 3 standard methods for non-billfish and 2 standard methods for billfish species. Remember, don’t pull a tape measure over the fish; instead lay the fish down on top of a ruler or measuring tape. All measurements should start at the tip of the snout, and the end point depends on what type of measurement you are taking:

Costa Rica Sailfish Tagging