Fish Weight Formula

[dolomieu]

My friend caught a big LMB today, but we didn't have a scale to weigh her.

We did take length and girth measurements and I've used a few formulas from different sites and the weights range from 8.88-10.5 lbs. (the one on here gives 10.44)

Does the IGFA have a species specific formula??

Anyone ever test a specific formula with a known weight?

The measurements are 24" TL x 18.5".

Thanks

[D4u2s0t]

8.8-10.5 is about as close as you'll ever get with an estimate.  next time just bring a scale, they're very cheap.

[RoLo]

Unless you're in a tournament or dealing with a Personal Best, exact weight is not important.

To reduce traumatic stress, there's a growing number of recreational anglers where I live

who might take a quick length measurement but that's it. They don't bother the bass

with girth measurements and weight scalings.

Length is more telling of age, while Girth is a reflection of forage base and stomach contents.

On average, a 24" bass is an 8 lb fish, give or take a pound based on physique (Paunchy <-> Svelte).

In the same vein, the proverbial 9-pound bass has a mean length of 25 inches.

Morbidly obese fish need not apply ;D

Roger

[D4u2s0t]

Like rolo said, I don't weigh unless it's a good one anymore.  After enough time with the scale, you actually get good at knowing the weights, instead of never using a scale and thinking your 3lber is a "solid 7" lol. 

[dolomieu]

Yeah,  I hate when people catch a 4 lber and say its 6. That's why I want the best estimate.

I'm pretty good at estimating weights below 5 lbs, but neither of us had ever caught one that big.

I think we're fairly safe saying it was a 9 lber. I'm sure it was a very gravid female.

[Raul]

Follow these steps:

1.- Measure length and girth

2.- Log to BR

3.- Click on the Tacklebox box above

4.- Click on Fish weight calculator

5.- Select species, enter length and girth

6.- Click on Calculate

7.- Voilá

BR 's fish calculator is the most accurate of any I 've tried, the margin of error is minimal ( a few tenths of an ounce ) when compared to an actual weight obtained with a good scale.

[K_Mac]

With a grip scale an accurate weight can be taken in less time than it takes to take a photo for most of us. I see no reason to weigh a smaller fish, but no harm in weighing a larger one. I think knowing the exact weight of a big fish is a good thing.

[WRB]

The formula I use is; L X L X G /1200 = weight in lbs.

Any formula is only as good as the measurements.

The length for this formula is the bass laying on a flat surface, mouth closed and measured from the tip of the closed mouth to the end of the tail center, down the lateral line.

The girth is measured around the bass at the widest area with the dorsal fin down.

I often use a length of my line to measure a big bass, if I don't have a scale; one piece for the length and another for the girth and tie an over hand knot in the girth piece.

Your bass weighs 8.88 lbs +/- 5% based on the measurements you posted.

A good digital scale is more accurate. The Jennings UltraSport 30 is very accurate within 0.2% and can be certified. Most "fish" digital scales are only accurate within 2% and dependant on battery strength.

WRB

[RoLo]

Yeah, I hate when people catch a 4 lber and say its 6. That's why I want the best estimate.

I'm pretty good at estimating weights below 5 lbs, but neither of us had ever caught one that big.

I think we're fairly safe saying it was a 9 lber. I'm sure it was a very gravid female.

You're thinking is right On-The-Money

Once you've boated a gaggle of hefty bass, you'll already be thinking about the next bass,

while still photographing the last bass, because the window of opportunity is very narrow.

(my two best largemouth bass were taken within minutes of one another)

Furthermore, the stress of girth measurement and weight scaling is only added to the photo opp.

As I stated above, a well-proportioned 24" bass will weigh shockingly close to 8 pounds,

give or take one pound for paunch or svelte. The mean girth of a 24" x 8-lb bass is 16.5".

Since the girth of your bass was two inches heftier than the mean, you're perfectly justified

in thinking of that fish as a 9-lb bass, which not coincidentally represents a stubborn weight plateau.

Roger

[Glenn]

Follow these steps:

1.- Measure length and girth

2.- Log to BR

3.- Click on the Tacklebox box above

4.- Click on Fish weight calculator

5.- Select species, enter length and girth

6.- Click on Calculate

7.- Voilá

BR 's fish calculator is the most accurate of any I 've tried, the margin of error is minimal ( a few tenths of an ounce ) when compared to an actual weight obtained with a good scale.

Thanks Raul. We use an algorithm that's unlike any other used.  While it's based upon actual measurements and corresponding weights, it's still an estimation, and will never be exact due to many, many variables that cannot be predicted.

[Muad Dib]

On average, a 24" bass is an 8 lb fish, give or take a pound based on physique (Paunchy <-> Svelte).

In the same vein, the proverbial 9-pound bass has a mean length of 25 inches.

Morbidly obese fish need not apply 

Roger

hahah my avatar is 7 lbs and change and it was 20 inches on the dot. haha my luck when i released it and not weighing it is that i caught it again. so catch yours again and if unable i think you should  see a psychiafish. haha

[Mattlures]

I specifificaly remember weighing a bass that measured 24x18. It weighed 8lbs 10oz.

Your fish would be right around 9lbs.

[WRB]

No calculation can replace an accurate weight on a certified scale or even a scale within 2%.

If we use the BR calculator or the IGFA formula on the current 2 world record largemouth bass, they differ by several pounds;

BR Perry bass = 28.61 lbs, Kurita bass = 24.24 lbs

IGFA Perry bass = 32.49 lbs, Kurita bass = 30.69 lbs

My formula Perry bass = 24.32 lbs, Kurita bass = 20.60 lbs. Keep in mind the 5% factor when calculating bass; a 22.25 lbs bass = 1.11 lb error factor @ 5%.

8.9 lb @ 5% = .44 lbs or 8.4 lbs 9.3 lbs using my formula L X L X G /1200 = weight.

Buy a accurate scale if you expect an exact weight.

Perry bass = 32" X 28.5"

Kurita bass = 29.2" X 29"

Normal bodied LMB girth = 75-80% of the length.

Heavy bodied LMB girth = 90-95% of the length.

WRB

[Lund Explorer]

Can I add to the confusion?

Glenn has the BR Calculator.

WRB has L x L x G / 1200 = Weight.

Mine?  From an old formula in In-Fishermen L x L x L / 1600 = Weight.

The simple fact is like WRB said, you want accuracy you use a certified scale.  Every other method will be fairly accurate within a certain size range and then begin to vary outside of that range.

For comparison, my calculation says your 24" bass would weigh in at 8.64lbs or 8lb 10oz.