BLUE FIN: Formula for calculating weight.

SSUfish

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Call me crazy but isn't that the formula for yellowfin? It sounded like the guys on the Hi Count who called in a 270 were grossly overestimating, possibly from using this formula. It's a good idea, but I don't know...is there data to support it for BFT?
 

makairaa

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Call me crazy but isn't that the formula for yellowfin? It sounded like the guys on the Hi Count who called in a 270 were grossly overestimating, possibly from using this formula. It's a good idea, but I don't know...is there data to support it for BFT?
Any formula is only as good as the data inputted. I assume to be as far off as that boat was that they measured wrong or did the calculations wrong. The fish formula should work for most fish. You are basically finding how many cubic inches the fish is and multiplying it by a conversion to get lbs. The main variable would be the density of the meat and how much space in the belly that would be less dense than the meat or bone. So unless bluefin meat weighs more or less than yellowfin meat for the same cubic inch it should not matter.
 
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kimorb

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The number you divide by is dependent on the geometry of the fish. Bluefin have a similar but slightly different shape to yellowfin. In the case of rainbow trout you divide by 740.
 
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makairaa

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The number you divide by is dependent on the geometry of the fish. Bluefin have a similar but slightly different shape to yellowfin. In the case of rainbow trout you divide by 740.
The divisible number might be different but is based on tissue weight difference. If shape was the issue you would change where or how you measure the fish. By multiplying the length times the girth you are establishing how much space the fish takes up. The more I think about it, it probably is some of both.
 
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yessokk

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SSU Wrote:

."Call me crazy but isn't that the formula for yellowfin? It sounded like the guys on the Hi Count who called in a 270 were grossly overestimating, possibly from using this formula. It's a good idea, but I don't know...is there data to support it for BFT?"

The formula was derived from a Google search...... Blue Fin Weight Formula.
A ton of info came up.
The formula also has a fudge factor.... if the BF is a Fatty add 10% if its a Skinny Minni subtract 10%.
Now that call is subjective for sure but it sure beats a weight estimate by an adrenaline infused
angler.
Walt
 
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ernie_kru

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Call me crazy but isn't that the formula for yellowfin? It sounded like the guys on the Hi Count who called in a 270 were grossly overestimating, possibly from using this formula. It's a good idea, but I don't know...is there data to support it for BFT?
I believe what happened for the big fish was that they called in a calculated 217lbs and the guy on the other end of the radio heard 270lbs... Just a guess though..
 

fujirose

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"I believe what happened for the big fish was that they called in a calculated 217lbs and the guy on the other end of the radio heard 270lbs... Just a guess though.."

That is what was explained earlier, for the difference between the weights, makes perfect sense. Confirmation back over the radio by single digits would have prevented the misunderstanding; "two one seven" compared to "two seven zero".
 
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2nd time

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"I believe what happened for the big fish was that they called in a calculated 217lbs and the guy on the other end of the radio heard 270lbs... Just a guess though.."

That is what was explained earlier, for the difference between the weights, makes perfect sense. Confirmation back over the radio by single digits would have prevented the misunderstanding; "two one seven" compared to "two seven zero".
 
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Rabid Fish

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Any formula is only as good as the data inputted. I assume to be as far off as that boat was that they measured wrong or did the calculations wrong. The fish formula should work for most fish. You are basically finding how many cubic inches the fish is and multiplying it by a conversion to get lbs. The main variable would be the density of the meat and how much space in the belly that would be less dense than the meat or bone. So unless bluefin meat weighs more or less than yellowfin meat for the same cubic inch it should not matter.
Bingo. Higher fat content in BFT theoretically means lower weight per cubic inch, since muscle weighs more than fat. BFT also have bigger heads than YFT. It seems very possible if not likely the k=800 number needs to be adjusted slightly for BFT.
 

yessokk

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Call me crazy but isn't that the formula for yellowfin? It sounded like the guys on the Hi Count who called in a 270 were grossly overestimating, possibly from using this formula. It's a good idea, but I don't know...is there data to support it for BFT?

This is for a Yellow Fin Tuna but the IGFA confirms that it is also valid for Blue Fin. :)
Or any tuna for that matter.

May

How To Accurately Estimate A Tuna’s Weight
Posted by admin Published in General
On January 19, 1996 an apparent world record 376-pound tuna was officially weighed at Fisherman’s Landing by Corky Yokoe of Monterey Park. The fish was estimated at 376 pounds when it was caught. Royal Polaris skipper Frank LoPreste used taped measurements to get that figure.

The landing’s electronic scales are calibrated. They showed the fish weighed 376.4 pounds. I shot photos of the scales’ readout, and the pictures all showed the higher measurement.

Here’s how to determine the weight of a tuna, using this formula: Length times girth squared, divided by 800. In the case of Corky’s giant yellowfin, it worked like this:

Tuna Weight Formula

Girth (61 inches) squared equals 3721
multiplied by
Length (81 inches) equals 30140
divided by 800
equals 376.75 pounds


Or put it this way: Length times Girth squared, divided by 800 equals Weight.

Skipper Frank LoPreste commented that this (61” x 81”) tuna was one of the fattest he’d ever seen, but the formula still worked to within one pound.

An interesting note to Corky’s catch and its estimated measurement is that the fish didn’t appear to lose any weight in the brine hold, contrary to the predictions of those who said the salt draws moisture out of the fish. Rollo Heyn, then a Royal Polaris skipper, held that the brine hold causes virtually no weight loss. The weigh-in seemed to indicate Rollo was right.

Corky was granted the 130-pound line class record for yellowfin by the IGFA for his remarkable catch, made on January 5, 1996. The record is still in the book.
 
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BiggestT

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Fat vs muscle has little to do with it. The denominator (800 in this tuna formula) is about the mass and how much of the is carried along its length (i.e. shape). As one pointed out, they use a different number for trout. I recall talking to the IGFA and they derived a different number for largemouth bad over 10 lbs from all the submissions to their 10 lb bass club (do a deep search here as I know I’ve posted about it years ago). It fairly obvious from an educated eye that the body profile of a bluefin tuna is vastly different than a blue marlins. The bluefin tuna carries that max girth measurement for only a short portion of it’s length, whereas the blue marlin carries close to that max girth for a much longer portion of its length. Thus the denominator use for a bluefin tuna would be less accurate when used for a blue marlin.