After 35 minutes of straining against an unseen foe, arms and back sore from battling both the fish and an ill-fitted harness, you heave a sigh of relief when the double line knot finally breaks the surface. You suddenly realize that an end to this self-induced torture could be near at last. Adrenaline begins flowing through your body as you pump the remaining 40 feet of line to the boat.

Suddenly the billfish is tagged at boatside, the crew removes the hooks, and it kicks its massive tail to swim away — just that fast. The inevitable question pops out of your mouth: “How big?”

The game of estimating the size of a fish, a game that goes all the way back to our arms-spread-out, “it-was-this-big” childhoods. Anglers have the tendency to overestimate the weight of a catch, whether to unknowingly feed our own ego or because the water somehow magnifies our image of the fish.

Who cares? Judging by the people who gather around the weigh-in station at a tournament, we all do. How many times have you tried to out-guess the person next to you as the fish was hoisted up the scale?

But the need for tools that accurately gauge a fish’s weight upon release goes far beyond personal curiosity or dockside competitions.

The most obvious benefit to more accurate weight determination comes in the tournament setting, where crews must often make a tough decision when they catch a fish that hovers near either the event’s minimum weight requirement or near an open spot on the leader board. Accurate estimates help keep non-qualifying fish in the water instead of on the dock.

Perhaps a more important arena where accurate weights become necessary is the billfish tagging programs run by the National Marine Fisheries Service and The Billfish Foundation. Many fishermen have undoubtedly been involved in the tag-and-release of one or more species of billfish.

In the tagging process, the most vital component is the actual tag card, which contains various pieces of data, including an estimation of the fish’s size and weight. If the information on that tag card is not accurate, then that tagging card is not accurate, and that tagging effort was not only a vain act, it may in fact be detrimental to the tagging program’s aims.

Since billfish have a small tag-recapture rate, captains and crews often have no way to be sure their weight estimates are on target. Such a lack of accountability leaves egos free to roam, which explains why fish often weigh less when recovered than they were estimated to weigh when released months or years earlier.

Traditionally, crews rely on one method to gauge the weight of their catch: “eyeballing.” Unless you have experience working the state fair as a weight guesser, eyeballing is not an option if you’re looking for accuracy.

Those of you who routinely tag and release probably do so because you value the resource and understand the need for information by the scientific community.

Tagging carries with it considerable responsibility, and providing accurate data is no less important.