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Posts: 1291
Location: Hayward, Wisconsin | I've spent the last few days further researching fish weight formulas. First I checked out the bizzaro world of the Internet...had no idea that there were so many ridiculous formulas out there! In addition to the five I've already mentioned, I found the following that you probably wouldn't want to use:
Old Farmers Almanac (been around over 100 years) and the Ontario Federation of Anglers and Hunters (OFAH) both use a derivative of the standard formula; G X G X L/900. Note the 900 divisor lessens the weight nearly 7 pounds from the "regular" standard formula.
IGFA too, from what I could find, use a modified version of the standard formula wherein they use fork length instead of total length (at least for tuna, striped bass and marlin...could find no reference to muskies); G X G X FL/800. Perhaps that is why we find that the "regular" standard formula over states estimated muskie weights when used!
The Mepps website calculator determines the weight of the 55 X 30 muskie to be a mere 47.54 pounds.
Lac Suel Outpost was least generous with their formula (calculated on their web site) which finds our 55 X 30 weighing only 38.08 pounds!
Sports Afield magazine, when they ran a contest, used a Hannon type formula which only used length with an even higher divisor; L X L X L/3500 which puts the 55 incher at 47.54 pounds. This is obviously the same formula that Mepps is using.
Since girth is not involved, I believe we should summarily dismiss the length only formulas.
So, finding no obvious solution on the Internet, I went back to the four formulas that use both length and girth and did further research against my data base of mostly recent catches of jumbo muskies, both kept and released, and did some further work with them.
As discussed, I have found the standard formula (G X G X L/800) to consistently over state fish weight (perhaps about 3 inches of muskie tail beyond the "fork length" is where our problem is with this one...since we don't know exact fork length, I think we should dismiss this one too, especially since almost all muskie anglers want to know the total length of their fish as well as a good "estimated" weight.
The Wilkinson formula (G -.75 X G -.75 X L/800) is merely a derivative of the standard formula and was based on a small sample of Georgian Bay muskies in the 40 pound range. Therefore, we should dismiss this one too.
The Casselman/Crossman formula (0.0000418 {L/cm X G/cm} divided by 1444), unlike the previous two, uses the girth measurement only once, however as weights get higher, or should I say lengths and girths get bigger, weights grow exponentially beyond reason and outside known data. This formula was built using length, girth and weight data from 371 muskies. Therefore, for this reason and the obvious complexity of this formula, I have decided to put it aside.
The Crawford formula (L X G/25 -10) has consistently under stated fish weight when measured against known length and girth and weight of giant released or kept fish. However, it was always "close" to actual weight and therefore I thought it might be the most useable if tweaked a bit. So, I started crunching the numbers. The data base for this formula was over 700 muskies where length, girth and weight were known. The obvious thing to do here was to reduce the "minus" factor, which I finally reduced to 8. I crunched away and wonder of wonders, that seemed to do the trick!
This new formula, which I have dubbed “The Modified Crawford Formula” (L X G/25 minus 8) is simplistic in its use and extremely accurate throughout the data base range of weights used (from 53 to 61 ¼ pounds) without under stating any fish's weight. In addition, over stating of fish weight was extremely minimal with this new formula on this data base, ranging from +.16 pounds to +.68 pounds or .29% to 1.1% of actual known fish weight. None were under stated, a previous problem with the original formula, where the “minus” number was 10.
Based on this new formula, the "Mille Lacs Queen" comes in at an even 58 pounds!
Stay tuned!
Edited by Larry Ramsell 12/8/2015 7:56 AM
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Location: Grand Rapids, MI | "Giant" is relative to each angler, I consider giant 56" and/or over 45#, but that may not be what someone else considers giant. Can we put a number on "giant" for the sake of the formula? It seems to overstate the weight on some fish I've caught that were under 54". Example 52.5 x 25 comes in at 44.5#, there's no way that fish was over 41#. This"modified Crawford" seems much more accurate at lengths at or over 55, with 55x25 coming in at 47# and 56x27 coming in at 52.5#. It seems that it would be better to keep the subtraction at 10 for fish under 54" and 25" girth and apply 8 for fish over 54" with a girth of 25" or more. The real concern about any formula is that from water to water these fish aren't built the same. For example: the St Lawrence/Ottawa/GB/etc. fish are built differently than St Clair fish and 55x27 might be 51# from some places but will be 44# in LSC. |
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Posts: 8782
| Not asking you to do this, Larry, but do you suppose the "modified crawford formula" is accurate on fish in the 25# - 40# range? Perhaps the original formula and "minus factor" of 10 applies much more accurately to your "average" big fish?
This is kind of what I was getting at in my earlier post - maybe the formulas can be accurate if we use a different one for the largest fish as you've worked out above.
You've done the math with a substantial number of fish with known weights. Your margin of error is pretty #*^@ small.
I think you nailed it on that formula.
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Location: Contrarian Island | imo there are so many different builds on fish all over that a formula will never be 'accurate' across the board... it may be accurate for one kind of build like a Mille Lacs fish but then way off for a LSC fish...the only way to get an accurate weight is weigh it...plain and simple.
Edited by BNelson 12/8/2015 10:28 AM
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Posts: 1291
Location: Hayward, Wisconsin | Will:
Basically I modified the Crawford formula just for the bigger fish. The original formula can still be used on smaller fish. The majority of the over 700 muskies used by Crawford in developing his formula we in the smaller to mid size range. I in no way meant to completely disregard the original formula. Based on work I did trying to develop a point system, it takes a fish of 59 inches long with a girth of at least 28 inches to be in the ball park of a 55 X 30. A 57 X 29 would also get the job done.
The data base I used for the modification included fish from Mille Lacs, Georgian Bay and the St. Lawrence River and girth is girth, regardless of whether they are caught from Lake St. Clair or elsewhere. Again, this is merely an "educated estimate" of what a fish "may" have weighed had it been kept. The advantage in this formula of only using the girth number once helps to level the playing field from water to water.
EA: I believe I answered your query above. If not, let me know.
BNelson: You are absolutely correct, that is why I am constantly warning that any formula is merely and "estimate" of fish weight. What I am attempting to accomplish is to develop a formula that works to be very close on these super fish wherever they come from. I am still an advocate of using a certified scale if you wish to know for sure!
Edited by Larry Ramsell 12/8/2015 11:07 AM
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Location: 31 | Will, I echoed your concern with the Crawford formula with Larry as well. However, it does work well with these upper echelon fish, so perhaps a simple disclaimer that this formula may not apply to fish under xxx. BNelson makes a good point too, but then again it would only be an estimated unofficial weight... all that would be required is something that is fair across the board. IMHO a length only release category is dated, and does not do justice to super fish like the MQ, I would guess that 99 out of 100 of us would rather catch and release a fish like this vs a thin 57” for instance (although I certainly wouldn't turn that down either). The documentation provided for MQ certainly sets the standard for entertaining this idea.
I like the idea of the release category with an estimated weight, and having the most accurate formula is the logical starting point to begin a modern-day standard for catch and release. I think it would be great if Muskie 1st would entertain the idea of sponsoring an annual release contest, provided we can hash this out. We could have registered users vote on the rules and best formula to use... pretty sure we would not have to take a vote on what the first entry would be.
Edited by Jerry Newman 12/8/2015 11:23 AM
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Posts: 8782
| Yes, Larry, and thank you. |
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Location: Grand Rapids, MI | Larry Ramsell - 12/8/2015 11:57 AM The data base I used for the modification included fish from Mille Lacs, Georgian Bay and the St. Lawrence River and girth is girth, regardless of whether they are caught from Lake St. Clair or elsewhere. I can't agree with that, girth is NOT girth regardless of where they're caught. Girth as suggested to do by most is one measurement at the widest point and doesn't give a true representation of the fish. We're not measuring a cylinder that is equal from end to end, to have a formula that truly works for all fish there needs to be a way to get a better idea of the shape being evaluated.
I've always said to have a formula that would apply to all fish it would have to take two girth measurements at consistent locations as two locations would give a much better representation of the shape. My suggestion has always been to develop a formula that takes girth measurements directly behind the pectoral and pelvic fins. IMO this would eliminate "widest point" and would give the most accurate representation in a formula.
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Posts: 1291
Location: Hayward, Wisconsin | Will:
I respect your position. What I meant was a 30 inch girth is 30 inches regardless of where it is caught. Since one that size has never been caught from Lake St. Clair, you cannot be sure it wouldn't look like the Mille Lacs fish at 55 inches. I know what you are trying to say...I said the same thing many years ago. I determined from photographs from around the country, that there were "at least" six different body shapes and a formula would need to be developed for each one, requiring such a large number of samples of the upper echelon of weights that it is nearly impossible. I'm building as good a data base for these "giants" as I can, but you'll toss dirt on me before enough samples are gathered together and individual formula's developed. In the meantime, we'll go with what seems to be working best on today's giants from waters that are producing them.
On a side note, if any readers out there have measured length and girth of a super fish and weighed it before release, please let me know the details at [email protected]
Edited by Larry Ramsell 12/8/2015 11:51 AM
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Location: Grand Rapids, MI | Now I understand, we're on the same page. |
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Posts: 58
| I fished Lake Athabasca this fall for giant trout. They leave all the fish in cradles and weigh the fish by hooking the scale to the top of the cradle near the handles and quickly lifting them a few inches above the water line, then subtract the weight of their known wet cradle. This could easily be done with muskies if one was truly curious, even with our large musky "nets" i dont think it would stress or damage them its no more invasive than bumping them or pulling them out of the net a taking pics. |
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Location: Chisholm, MN | Larry, do you have photos of similar length and girth fish that we could compare builds from different lakes or strains from?
I find all this interesting, but I have only caught a couple of fish that I have even been interested in the weight. In my experience getting an accurate girth measurement has been difficult because I just don't want to stress the fish out. My measurements would be just ballpark for that reason. |
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Posts: 1291
Location: Hayward, Wisconsin | Kirby: naturally I have such photos, in fact dozens and dozens are in my current "Compendium". Dozens of others have been published here on this web site as well.
It doesn't necessarily take different lakes to produce the many different shapes of muskies. Not all fish in a particular water body are "cookie cutter" shapes.
I understand your not wanting to stress the fish out, but there are so few that really need a girth measurement taken, it is worth the effort. One of my suggestions is to permanently affix a soft measuring tape to a bump (measuring) board and accomplish both measurements in the same place and quickly.
Obviously, to establish a new release record (see: http://muskie.outdoorsfirst.com/articles/12.11.2015/9319/World.Reco...), more than just a "ballpark" measurement is required. |
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Posts: 28
| I was trying to estimate the weight of my GB fish this summer and found it ranging from 38-47 lbs. depending on the formula used. Didn't realize there was such a wide variation in formulas because I never caught a muskie big enough to really care. My fish this summer was 54.25" x 24.5". In your opinion Larry, what would be the best formula to use on that fish? Don't think the modified Crawford formula would be the best for this fish because it didn't have a super tanker girth. Thoughts? Thanks! |
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Posts: 1291
Location: Hayward, Wisconsin | Aaron B: The original Crawford formula (L X G/25 -10) puts it at 43.17 which would likely be fairly close. Congrats on a very nice fish! |
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Posts: 28
| Thanks Larry, it was the biggest fish I've ever held by far. I had to hold it up against my body to even support the fish. I give credit to the guy that can extend their arms and hold the fish out a bit for the pics. I had all I could do to support the fish and just ended up with a bit of slime all over my shirt! 
I knew it had to be close to 40 if not over so the Crawford makes sense and I love how easy it is to calculate. Thanks again for the input.
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Posts: 37
| When it comes to estimating the length and girth on a 50"plus muskie, I've seen the best guides miss on estimating the length! Why, because they see so few that big. They may be fairly accurate on the 40's but not the big girls! IMO you have to measure the fish correctly and use a standardized formula like Larry recommends or the data will be meaningless.
If you catch a record fish and want an accurate weight you have to kill the muskie which most prefer not to do. There are too many variables to net weighing in the boat plus human nature kicks in. I actually wish someone would catch a world record muskie, document it properly and end a lot of the controversy. Unfortunately, I suspect that fish doesn't exist so the modern day world record and modern day release is the best option available. |
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