Bass Fishing Forum - Westernbass.com

Calculate Bass Weight with Florida FWC Graph
You’re on lunch break from work and decide to toss a couple of casts into the park pond you pass every day. Suddenly, something big hits! Fortunately, the pond doesn’t contain too many obstacles and you manage to land one of the biggest bass you’ve ever seen. But you have no scale . . . All you can do is measure the bass length and girth with the tape measure you keep in your toolbox before releasing it: 27 inches long and 18 inches around. But the real question is, how much are you going to tell the guys back at the bass club it weighed?

Luckily for curious anglers, the relationship between a fish’s length and its weight is a fairly consistent one. The graph below, charting the weight and length of many individual bass, reveals that a nice, consistent relationship exists between the two. This is illustrated by the clustering together of the data points (dots) and the smooth curve that they make as a group. This graph displays information from bass surveyed from the L-67A Canal in Water Conservation Area 3.

This graph compares length and weight for 3,600 largemouth bass sampled from the L-67A Canal. Each dot represents one fish; most of the dots are so tightly clustered together that they are not individually visible.

One thing to keep in mind is that many fish change shape as they get larger. For example, bass anglers know that a big “hawg” has a much chunkier profile than a young “bank runner”. You can also see this in the above graph. Instead of a straight line formed by the grouping of dots (which would occur if weight was exactly proportional to length for bass of all sizes), there is an upward curve. In other words, as a bass gets longer it tends to weigh more per inch.

Does all this graphing and science have any practical application for anglers? Of course! There are various equations that have been developed to estimate bass weight based on its length and girth. Fortunately, FWC’s Bass Weight Calculator website saves you from doing the math: Just plug in your numbers and hit return! The first weight estimate displayed is the one FWC considers to be most accurate, but estimates using several other formulas are also provided for comparison. Plugging in your numbers from your park pond bass, you can tell your fishin’ buddies that your bass weighed about 11 pounds! (And you’ll definitely take your scale next time!)

So far, we’ve only talked about largemouth bass, but most fish will have a similar relationship between length and weight. Of course, the numbers (and ratio of weight to length) will be very different for a round bluegill than they will be for a long gar. For a biologist, length-weight data like this can reveal what health condition a fish is in, whether a fish’s shape changes as it grows, and other important information.The FWC's Bass Weight Calculator website will provide an accurate bass weight estimate from a length and girth measurement.
https://myfwc.com/fishing/freshwater/fi ... &utm_term=

Note that for TrophyCatch submissions, you MUST provide a readable weight-on-scale photo and we recommend that you always carry a scale with you — you never know when a trophy will show up in Florida! However, if you ever get caught without a scale, a length and girth measure can help you estimate the weight of your catch.

so who is going to take the time to figure out what the grams and millimeters are in inches and pounds?

For 10 years I measured and weight several hundred bass just keeping records between 1965-1975.
When I started catching 10 lb+ bass treid to use The IGFA formula Length X Girth X Girth divided by 800 = weight in lbs. IGFA length was mouth closed to base of the fork in tail.
Using my own data my formula Length X Length X girth divided by 1200 tracked closely to measured and weighed bass I caught during the decade. I also concluded the average Northern LMB bass body girth was 75% of the length. Florida strain in California lakes were heavy body bass with girth 90% of the length.
It's easy today to carry accurate digital scales and cell phone cameras. 40 years ago we had laboratory spring 25 lb scales with 2 oz graduations, close enough for bragging rights.
I suggest using the line from your reel cut to length and girth if you don't have a scale or tape measure. Use length X length X girth / 1200 =!lbs for a good calculated estimate.
Tom.

BASNFAN wrote:so who is going to take the time to figure out what the grams and millimeters are in inches and pounds?

Hmm, 3000grams is only 6.6lbs. Seems like the graph doesn't go high enough to cover what folks around here would consider a trophy sized fish.

[attachment=0]DVL LMB Weight at Length 2007-2019.PNG[/attachment]

Here is a graph of all LMB collected during fishery surveys at DVL from 2007-2019. The estimated weights at length are based upon the polynomial slope equation.To estimate the weight you simply solve for "Y" using the length as "X". The graph is easy to set up in Excel with lengths in mm on the X axis and weight in grams on the Y axis of fish collected.
(1 inch=25.4 mm)
(1 pound=454 grams)

My memory is a little vage exactly what LMB species DVL was planted with? I know Gusti planted both Smallmouth and Largemouth. The LMB I believe were transplants from San Diego lakes and more then likely F1 Florida strain.
The chart posted indictes length to girth ratio about 75%, poor girth growth for FLMB in California lakes.
Example; lake Castias in 1971 I caught a bass 28" long that weighed 12.4 lbs. In 1971 Casitas only had Northern strain LMB. 10 years later I caught a 28" long bass that weighed 18.6 lbs, lateral line pore scale of 72 count confirmed a FLMB. Length alone is misleading. You need both length and girth to calculate bass weight.
Tom
PS, pm if you want a picture of both bass

DVL LMB were all taken from Hodges and all FLMB. You'll notice data points above and below the slope equation line indicating individual fish may weigh more or less than what the equation can generate. While not perfect, the equation is valuable in establishing lake specific indicators and are used widely in fisheries management in general.

I have a reliable and accurate method of determining weight of bass:
Take the anglers report of fishes weight ..... and deduct 40% for true weight !

Lol