HERE YA GO

Its not that hard a formula....(in inches)length X girth squared divided by 800.
EX:
length- 74
girth- 53(x53)=2809
2809x74= 207,866
divide by 800= 259.8 lbs

 

According to Meirowitz, the approximate weight of a tuna can be estimated using a formula, which is the fork length multiplied by the girth squared divided by 800. This formula is considered a conservative estimate.

I can just eyeball the fish to within 5-10 pounds.

MakoMatt

 

The formula mentioned in the 2 previous posts applies to all round bodied fish. It is not specific to a single species. As such it under estimates some and over estimates other. For deep bodied fish like tuna, the formula usually comes up a little short. For long skinny fish like wahoo it over estimates. For flat fish its useless.

 

YFT Weight vs Length

(This post edited by KILSONG on 02/10/2005)

 

BFT Weight vs. Length

 

858

Divide by 858,
it provides more accurate results for YFT.

 

For the most part, the formula mentioned above (fork length multiplied by girth squared divided by 800) was reliable and, if anything, a little conservative with the YFT we caught on the Excel. In many cases, the formula was right on, but in a few cases it was low. For instance, the pool winner on the Excel trip went 276 pounds according to the formula. The fish was finally weighed in at 292. One of my fish, which was third place in the pool, went 230 pounds according to the formula. That fish finally weighed in at 259. Both those fish were really thick in the tail, and we think that made the difference.

HJ, I think if you divided by 858 with YFT, the number would be too low. I don't recall any fish that were finally weighed weighing less than the formula - even when dividing by 800. I think dividing by 858 would result in all fish being too light according to the formula. JMHO.

(This post edited by Meirowitz on 02/10/2005)

 

800 works better for YFT over 150 lbs.

858 is more accurate for YFT below 150, which is what he will encounter in Venice, LA.

The easiest solution is to use the length/weight chart Kil posted.
It will be near impossible to get a GIRTH measurement on tuna being held boatside for release.

 

ie. Wahoo you would divide by 720

 

HJ, the charts that Kil posted appear to be a bit conservative. For instance, on the Moorehead City trip, Dennis Braid caught a giant BFT that measured 97 inches fork length. The estimates performed on the TAG boat revealed that fish was well over 500 pounds. Yet, according to the chart that Kil posted, a 97 inch fish would weigh around 465 pounds.

(This post edited by Meirowitz on 02/10/2005)

 

Dick,

Weight/Length charts are an estimate.
They are calculated to represent the AVERAGE weight at a particular length.
If a fish is deeper bodied, then of course it will weight more, if it long and lean, then less. Measuring the girth helps fine tune the estimate.

In the case of catch and release of larger fish on a CHARTER boat, accurately measuring girth will be very difficult, if not impossible, so one is stuck using a length chart. Even measuring length of the fish while in the water will not be precise either.

If you find the calculations too conservative, then just do what most fisherman do, exaggerate the size.

 

Thanks for all your help, everybody. I was familiar with the "divide by 800" formula, but was unsure how well it applied to tuna. I'd seen the charts before too. I guess they would be the best option if the fish is left in the water. As far as tuna over 150 in Venice; we're hoping to run into a few of those-there was a 198 caught the other day!
Meirowitz, I read the discussion on your trip to NC with Dennis Braid, and I've gotta say it was fantastic! Doing that is "on my list" BIG-TIME! That must have been incredible feeling the power of those fish, and being able to put so much pressure on them. Doing it with someone who is as helpful and knowledgeable as Dennis Braid must have been a pleasure.

 

is that a good way to figure out the weight of your.....sausage?

 

Calculating

Lets see -fork length x girth squared divided by 800---yes that may work-Gulp--

 

LkyLindy you owe me!

One new keyboard. When I saw that picture, my breakfast immediately deposited itself all over my see board.