Length-Weight Relationship for Xiphias gladius-Best Formula?

[ReelIntubaiter]

Hello Fellow Swordfisherman:
Since most of us don't have access to scales capable of weighing our larger fish we must revert to mathematical formulas which estimate the length-weight relationship. The most commonly used formula for weight estimation is length (LJFL) X girth X girth divided by 800.
Our recent catch aboard the the FreeJumper has a weight of 240 lbs by this method of calculation. When James reported the catch he was surprised that NMFS calculated the weight through their "proprietary method" at 313 lbs. This brings to question the accuracy of our most commonly used method. A friend of mine at NOAA provided me a link with a lenth-weight calculator for Swordfish in the USA. Here's the link:

http://www.fishbase.org/PopDyn/FishL...b=3.2424645287

This site uses the length in cm's and calculates a weight in kg's.

I would like to obtain data (LJFL and girth) of fish actually weighed on a scale, preferably from previous tournament records, and test both formulas to see which is most accurate. I can volunteer to compile the data and present the results to this forum. Any thoughts?

All data can be e-mailed to me and I can present the results when data from approximately 100 fish is obtained.

[RiskTaker]

Reel Intubaitor:

Forget about it... if you know what I mean.... the fish formula (W = L x G xG /800(in.)) The formula is just an approximation and I suspect it does not hold up for all sizes of swordfish. Maybe you could tweek the divisor for different ranges of fish size or just jump straight to the lookup chart.

But your experience and example demonstrates that the two methods differ by too much to make one or both methods to hold up. (I bet you that the NMFS method is already to lookup chart we seek.) :lol:

I have been suggesting EXACTLY what you are requesting for a long time now. The formula is a vague estimate of where you are at. In particular, because real life does not adhere to the ideal model that you learn in school, nor the formula that is presented to you today on the internet/forum.

WE NEED TO HAVE A LENGTH AND GIRTH (TO WEIGHT) RANGE CHART.

This does not require any mathamatics, just a few measured weights from scales that are reasonably calibrated, along with the dimensions, length and girth.

The information will still be an estimate for other fish fitting the profile, but I do believe that it will be a lot closer for fish through the entire range. A single formula rarely works throughout the entire range of fish sizes.

ReelIntubaitor, ----- Unfortunately to say,this information is already documented somewhere. I just not have been able to find it. But I hear you loud and clear: a basic look up chart is where it is at.

We just need to get it posted on this forum: PLAIN and SIMPLE

P.S. - Great job on posting the link to a swordfish calculator. Time to go push some more buttons. Either that or put my electrician hat on. Ooops he come wifey, better get the hat on.

[ReelIntubaiter]

RT,
We need to talk to some of the Swordfishing tournament coordinators to obtain sufficient data and develope a reliable calculator/chart. I live too far down south to join the SE Swordfishing club. Maybe you have contacts? What about you Mike (moderator)?

[RiskTaker]

Reel Intubaitor:

Yeah, I will ping Drew (Darkside). Maybe he has some recorded data from the swordfish Tournaments he puts together.

Drew: Consider yourself pinged. Can you help out with some numbers?

Just because you live in Miami does not mean that you cannot make it to the SESC club meetings. You are only an hour away at the most and it is any easy drive to get to the place. These meetings are usually fun when you start chit chatting with a few folks. They don't typically happen every month, more like 4-5 times a year or so. That should not be too much of a drag if you have a positive mindset to attend. Consider yourself invited if you want to come as a guest at the next meeting.

I get down to Miami all the time for fun stuff. The drive is a snap as long as you don't get caught in traffic. I'll be down your way in 3 weeks since I signed up as an observer for the Mayor's Cup Tournament. It should be a lot of fun over at Monty's. Maybe get lucky and get on a Professional boat too.

Did you put a dent in all that fish yet?

[LETSRIDE]

in the hydraglow winter fest we had a fish calculate out to 131lbs with L x G x G/800 on the scale he went 132.8

[ReelIntubaiter]

Originally Posted by RiskTaker

Consider yourself invited if you want to come as a guest at the next meeting.

Thanks for the invite RT. Most of the meetings are weekdays and almost never compatible with my work schedule. i'll do my best.

I'll be down your way in 3 weeks since I signed up as an observer for the Mayor's Cup Tournament.

.

I'm fishing the Mayor's on a friends boat. GHope to meet you then.

Did you put a dent in all that fish yet?

Unfortunately I don't like eating Swordfish but I have many friends that do. We split the fish four ways. I vaccuum pack my steaks and give them away to friends and family. It doesn't go to waste.

[RiskTaker]

Originally Posted by "ReelIntubaiter [quote

Unfortunately I don't like eating Swordfish but I have many friends that do.....

:roflmao: :roflmao: :roflmao:

Can I be your friend too?

See you at Monty's. And I'll have a backup cooler in the car. Which boat are you on?

[ReelIntubaiter]

Originally Posted by RiskTaker

See you at Monty's. And I'll have a backup cooler in the car. Which boat are you on?

I'll be on a 29ft SeaVee "Voodoo child". See ya there.

[CAPTINMITCH]

As I posted on this thread:
http://www.swordfishingcentral.com/f...784d6 28e7dbd

the formula is generally pretty close in my experience. I tend to find it works out between 5-10% light. Some of the difference can be accounted for by stomach contents and some by body shape. I doubt you will ever find a one=size fits all formula since we've all seen how fat some of these fish can be.

[RiskTaker]

Mitch:

Have you tried that other formula that Reel Intubaiter posted the link on?
5 - 10% error sounds fine to me. But if you trust any of the information in the initial post of this thread the error, compared to another formula was differing by more than 25%. And that was for a fish right in the middle of the range. When I have a chance I will try punching in some side-by side numbers and perhaps throw in a few weighed examples in a separate column and we can see how they correlate. Unless you may happen to have something like that on an Excel spreadsheet already?

But hopefully it will not be too difficult to round up a list of weighed examples. Either way, if it is by formula or lookup chart the other one can provide a cross check, without the luxury of having a scale handy.

P.S. - Haven't had any luck hooking up using a baited Salami yet, but there are rumors that Banana peels may work in a pinch. Although, I think I will give some of those artificial squid a try as a redundancy to a reel squid

[Darkside]

This is a good topic but no 2 fish are alike. I have all the statics from all of my tournaments, the only thing they will prove is no formula works 100% of the time. I have seen fish 66" go almost 200lbs and caught fish that were78" that were only 225lbs. The thing with swords is some have big heads and no stomach some have small heads and big stomachs. The most important thing with the formulas is that their calculations are from only 2 measurements, some fish have weight all the way thru their tails. If somehow anal girth could be entered into the formula i think the weights would be alot more accurate. The only way to get true weight of a fish is for them to be hung on the scales.

[RiskTaker]

Hey Darkside:

Yep, that is the statement of variation that I was putting my confidence in.

So the idea is to construct a lookup chart: just like we do for people: light medium and large frame for example. It still provides a range but you are at least dialed into the "correct zone". Something these formuls may not quite do, in simple linear, or X2 fashion.

There can be LFJL, Girth as well as a general descriptor, Like fatty, or medium or skinny, just as you describe with the Big Head or fat tail variations.

So if you had a 66" without a scale and did not know any better from your own experiences you could probably see a range of weights.

125-135 lb. 140-160 175-200 215 max. depending on the fish's frame.

That may actually be easier than plugging in number to a formula.

72" big fatty as a general description, Look up 200-225 lbs. but could also be as light as.... or some heavy weights at 240 lb.

If we can hook up with some of your data, I can post it into an Excel format. Then Mike G. could post it somewhere on this forum as a reference, or as he chooses to do. ( I can call you or we can talk at the next SESC meeting or whatever works for you.)

[quack quack]

Big anal girth? J-LO fish :lol:

[PURPLE FEVER]

How about bill length? Doesn't a longer bill indicate a bigger fish? Oh yeah ,Bills are like -icks you can be small and have a big one and you can be big and have a small one :lol: A long liner friend told me about a chart that they use its in cm and kilos it may be similar to the one referred to earlier.