At one time I had found a link on this forum to relative weight charts for multiple species of fish that were created by Steven Bardin. That link no longer exists. These charts were made in Microsoft excel so you could chart your fish length and size and then in another column it would show the relative weight for that fish. It also showed the mean relative weight for all your fish entered and a graph showing your relative weights to the standard for all your fish. I still have the one for largemouth bass that I modified for my personal lake but cannot find the ones for all the other species like bluegill black crappie, wiper, and catfish. Does anyone have anything like this for the other species besides largemouth. I need to track the weights as we do corrective actions to our lake to track the progress or lack thereof over the coming years. If someone knows the calculations that take the length and weight of your current fish and compares it to the average constant value that then gives you the relative weight percentage of that species I’d then be able to use the largemouth excel as a base and modify it with the calculation of the other species to make the excel for that other species. Any help would be appreciated.
I actually just looked this up and used it for the first time myself. Bob shared this several years ago, before I had a population to monitor. Hope this helps!
Where W is the actual weight of the fish being measured and Ws is the standard weight for a fish of that length. The standard weight equations are actually the key to success with this technique, and biologists worked hard to develop reliable standards. In the pages to follow, we will provide standard weight tables in inches and pounds for your use. Fishery biologists often use millimeters and grams for their measurements because of increased accuracy and precision, but the inches-pounds tables will work well to help you assess the fish in your ponds. We have seen Wr values that range from the upper 50s to the 160s for a variety of fish species. Fish in the upper 50’s are so thin they are barely alive. Those at 140 or above look like plump footballs. Most biologists target Wr values of perhaps 90-100 as being acceptable. Please note that a Wr value of 100 is NOT an average. It actually means that all across their range, and across all seasons, 25% of the Largemouth Bass will have a Wr value greater than 100, while 75% will be less than 100. So, a Wr value of 100 is an above-average target, generally speaking.
RW is based on a " standard weight" calculated by theoretically taking the weight and length of a species across all locations. Problem is that data base does not exist. Many studies on this and the possible shortcomings with the process. There should really be standard weights by geographic locations. A standard fish in GA is not the same as one in MI. Also a standard weight in March is not a standard weight in Aug or Dec.
Having said that so readers will know to take the results with a grain of salt - RW is still a very good tool !!!
^^ I agree. One fishing trips' measurement is not a concrete measurement to be applied to the pond for a long length of time. Rather it's a trend that you keep track of during the year. If fish from the same week/month year to year are dropping in RW, then you have to do something NOW because you are already behind the curve.
My SMB , BG, and YP have been stocked , coming up on 3 years soon. The thought a couple nights ago was " is their weight or length where it should be for their age ". In reflection , is this the wrong question ? Too many variables from BOW to BOW ? Also not knowing their true age when received from the fish dealer . The real question is, are my fish at a healthy weight for their length ? If RW is at 85-115 % then forage has been there, through out its life so far , water has been reasonably happy , if weight and length RW is there then I should be happy with growth , for time they've been residents in my pond.. Forget how old, compared to any bench mark, and be happy with healthy fish, and healthy fish are those within a reasonable % of RW ? Fish at what ever age, are growing at the proper speed for that fish, in that BOW, at that Latitude , at that elevation if it is close to 100% on RW Scale ? Next question, I have not seen a RW scale for Okla. , with RW being taken with a grain of salt, but a good tool , if my fish match up to the RW for Pa. , is this close enough ? Within 2 or 3 % ? Sorry if ridiculous question , still solidly a guppy, a guppy that is struggling to make his RW %.
Age isn't on the charts, but if you see a a fish that is small with abnormally large eyes, then it may not be growing as fast as it should be.
Fish pre-spawn will be much heavier than fish post spawn. Up to 30+% heavier..... I don't know of any regional RW charts. Look in the archives here for a chart, that's what I go by. I have had Smallmouth Bass at 16" be right at a pound, and I've had a Largemouth Bass at 18.5" be 5 pounds 15 ounces. The more you use it the more you get a feel for it.
Still a rookie at this too, but I'll give you a bit of my plan and hopefully my understanding at the same time.
I have two excel based spreadsheets in use for the pond. The first is one I created using web-based search results on RW for the various species we either have in the pond or will have at some point. My first Excel file has data for Species stocked into the pond, Qty of each stocking in either lbs (FHM & GSH), or units of each in the case of BG, RES, YP, LMB. There was a tab created on this file to list length and weight of each species we catch that shows the RW of the fish we catch in the case of our BG, RES, YP, and LMB. Another tab on the file is our tracker for water conditions (visible conditions), PH, Temp, Alkalinity, Time and Date collected. There are no fancy graphs in this file because I'm not an excel master. My hopes for this file are to track our progress of the pond over time. I wasn't concerned so much about the geographic data for RW as much as having something there to compare to. Each pond or lake is different, but this sheet does give a baseline of info that over time will be valuable to me.
I did request the file from newly inducted Hall of Famer Bob Lusk. It makes my simple excel file look like I chiseled it with hammer, stone tablet but it's also locked. You can track only what it will allow you to track. Some species and pond data inputs are not available on it. Not to take away from it...the excel file Bob sent is nothing short of AMAZING.
So, my plan is to input as frequently as I can on both sheets. If fish are added, water conditions checked....we note it on excel file 1. If we fertilize, add chems, add plants or habitat again it's noted on excel file 1. If we sample fish we note it on both files, unless it's yellow perch in which case we note it on excel file 1. Culling fish happens on excel file 1 as I don't think the Pond Boss one allows you so show where you cull fish, but for me....I think this is important to track as this is the maintenance of the pond. I've seen several comments here on the forums when people are having problems and the recommendations are based on data the pond manager has. Most times the data provided when asking for help doesn't have definitive data to back it up. The better the data...the better the advice.
I agree on the RW over time is what we want to see the trend on. If data is input over time we should be able to see the RW improve or wain. If it improves over time we pat ourselves on the back and continue with the maintenance of the pond. If it wains over time we change our plan to match what the fish are telling us the need us to do. Gaps in recruitment should also be evidenced as well. I've fished the pond over the course of a month and only caught 1 3-5" bluegill would be an indicator to me that there is a problem coming or a minimum that I need to investigate why I'm not seeing them. I'm seeing a ton of new fry in the shallows, look at all those fancy BG beds or lack there of....
I'd hazard a guess the only way to really tell the age of the fish would be pit tagging them when stocked or guessing when looking at the newly recruited caught during some sort of sampling. I've heard the word "jumper" being used relating to the best of the best new recruits growing at much faster rates than the bulk of the recruits in the pond. It may be possible for these "jumpers" to surpass the previous years slower growers. When we stocked our YP recently the fish supplier mentioned they liked to keep the some or all of the jumpers to better their genetics.
1) Remember that your data is only of the fish that you can catch. There will be fish that you may not be able to catch. That's where periodic electroshock surveys help.
2) When weighing and measuring fish, have all the stuff ready before the fish comes out of the water, and make sure that you take all the precautions necessary to minimize handling of the fish to minimize the stress/damage to the fish. I see people using a hook in the gill area to weigh the fish. not good.... for the smaller fish, here's a thought. Look at getting a bag with handles, fill it with a quart or 2 of water, hang the bag, zero the scale. Put the fish in the bag and you can weigh the fish. Get a bump board, wet it and then measure the fish. If you can get the fish back into the water within 30 seconds, great! but shoot for less than a minute out of water.
3) I'd initially cull any fish that weigh under 80% RW BUT not take the RW until a month or so post spawn for that species. The more fish you get a RW on the more accurate your data will be.
There are two ways to check the age of a fish. One way allows the fish to live another day, the other requires killing the fish and using a microscope. You can age fish by looking at a single scale and reading the rings like reading the rings on a tree stump. Ditto for reading the rings in the otolith of the fish, but you have to kill the fish to do that, crack/slice the otolith, then look at it under a microscope to count the rings.
I did get a copy from Bob on his but his are a little more complex than what I’m looking for but really good. I was able to get Wr equations for the calculation of multiple species from my state fisheries biologist. I’ll share those later. They are however in mm for length and grams for weight so to use them there must be a conversion done of your going to go with lbs and inches and I don’t know how to do that.ill list those standard equations here on another post tomorrow hopefully. I was also able to get ahold of Steven and get some information from him as well and if I get spreadsheets generically made I’ll try to find a way to share them also. Steven has relative weight charts for quite a few species fish on his txprolake website under the fish section.
There are two online sources of length weight relationships that I am aware of. They have been around a while so some fish may be out of date. Here is one:
More often I will take a current chart and regress the formula underlying the chart. The function in decimal is a power function, but this can be linearized by taking the logarithm of both sides of the power equation. Being now linear, one only need two points to resolve the coefficients. Once you have a spreadsheet, you can regress any chart for any fish. The method goes like this.
You need 4 columns. Length, Weight, Log10(Length), and Log10(Weight). Put the labels for these in the cells A1,B1,C1,D1 respectively.
In column A enter the smallest length in A2 and the longest length in A3. In column B, enter the corresponding weights. In cell C2 enter the formula =LOG10(A2) and then copy that formula to C3. In cell D2 enter the formula =LOG10(B2) and then copy the formula to D3.
You are now ready to regress the formula Log10(W) = Log10(a) + b* Log10(Length). Log10(a) is the intercept and (b) is the slope of the linearized function. In cell F1 enter "Intercept" and in cell G1 enter "Slope". In F2 enter the equation =INTERCEPT(D2:D3,C2:C3). In G2 enter the equation =SLOPE(D2:D3,C2:C3). And there you have it. The equation that uses these coefficients to compute standard weight is SW= 10^(intercept coefficient + slope * LOG10(length)).
I like to use the power relationship instead. It is in the form:
SW =afactor * Length^Slope where afactor = 10^Intercept.
If you prefer this too, just add the equation into F3 =10^F2. Just substitute the value of F3 for afactor above.
Last edited by jpsdad; 03/28/2408:06 AM.
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
Why don't people look in the archives for the answer? There's a TON of data there if you'd take a look. This IS POND BOSS after all, and that is why we set up the archives.
So, I guess this makes site #3 where the data is on the internet...............................................
Why don't people look in the archives for the answer? There's a TON of data there if you'd take a look. This IS POND BOSS after all, and that is why we set up the archives.
So, I guess this makes site #3 where the data is on the internet...............................................
That thread doesn't answer the OP's question. He isn't asking for charts. Charts are all over the internet. In fact, not one of the charts in the reference above are sourced from POND BOSS. They are sourced to charts found on other websites. Give credit where due ... maybe?
Anyways, the OP wanted help with the coefficients that model individual species so he could put them in an excel spreadsheet. A chart is like a driving a nail with a rock. What does he do when he goes to your referenced charts and finds his length measurement lies between lengths of the chart? I suppose he could interpolate and such and continually hand enter the standard weights so he can calculate RW. But I am sure that he wanted a hammer to drive nails with. He wanted to model the standard weights with equations.
I am not sure what you were so quick to take issue with. The references that tabled the coefficients for many species ... or my showing him how to determine the coefficients on his own. Just chill. If the original poster is using excel, he can make use of my post.
Last edited by jpsdad; 03/28/2404:59 PM.
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
No big issue, I just didn't understand why an excel (or similar) chart was needed because I don't use my phone or computer when in the boat. Too big of a chance of it going swimming.
Getting a weight between the lines is easy. Simple math.
I personally like the ability to log the info into excel so I can learn to watch the trend vs relying on my memory. I can always log the info after coming back from the pond if I scribble down some quick notes on what I did, caught and observed while at the pond.
It could be anything from fish, water temp, ambient temp, weed growth, saw a heron, ducks and geese are migrating, caught my first fish, saw fish with fungus, PH, alkalinity, turbidity, secchi disk readings, yellow perch spawning.....
My memory is faulty, and my spelling is probably worse....excel remembers everything as long as I save the data.
No big issue, I just didn't understand why an excel (or similar) chart was needed because I don't use my phone or computer when in the boat. Too big of a chance of it going swimming.
I see. I wouldn't bring my computer out in the boat either. All I was trying to do was help the OP with his question. Just trying to help him accomplish what he would like to do. Never gave a thought to the unfortunate circumstance of computers going swimming.
Originally Posted by esshup
Getting a weight between the lines is easy. Simple math.
If only it were. The function underlying the chart is a power function. It is not linear. One will always miscalculate the interpolation if using a linear interpolation ... that is ... except for a single point between the lines where it will work. Not saying you can't do that in a pinch, but it will almost always be a "kind of artsy", incorrect, mathematically wrong way to do it.
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
But, look at the charts that are in the archives. Take LMB for example. A 22" LMB should be 5.9#, a 23" 6.8#. If a 22.5" LMB is much either side of 6.3#, how critical is that to figuring out the RW? You are looking for trends in the pond, not absolute numbers down to the 3rd decimal.
Say you have 2 different 22.5" LMB One weighs 6.3#, the other weighs 6.5# because it just recently ate a 7" BG. Will that 0.2# be enough of a weight difference to make a decision to change how the LMB are managed in the pond?
What I'm trying to say is that once you start managing ponds in the real world, it's not critical that the numbers are spot on because of all the variables that are in the pond. You are looking for trends, and the 1" weight change is fine enough of a measurement to see trends.
Please do the power function calculation on a LMB that is 22.25", 22.5" and 22.75" and list what the weights are. How much do they differentiate from the weights calculated from a linear function?
The percent error from interpolation of the mid points ranges from 1.4% to 0.20% for lengths between 8.5" to 22.5". The error is not large and I should have added to incorrect and wrong mathematically ... that interpolation is a practical field method with acceptable error.
I see RW as a way to confirm that individual LMB are fulfilling their genetic potential to grow in length. They are going to put excess energy to use growing their frame .... and if they consume more than that ... that will pack on RW.
The consumption required to grow a 21" 100 RW LMB growing to 22" 120 RW is roughly the same as growing a 21" 80 RW LMB to 22" 120 RW. Applying energetics, the difference in consumption is less than 2%. IOWs there may be little advantage to culling one over the other. Removing either fish should free enough forage for the surviving fish to grow at its potential.
For two fish at the same length and 2 different RWs, RW tells about their consumption over the past 12 months. A 120 RW LMB consumed 20% more than its peer at 100%. Why? Just a better competitor (but not by a lot). The average daily difference in consumption is only 0.05% more for the 120 RW LMB than the 100 RW LMB. Every few days, the 120 RW LMB ate a fish that the 100 RW LMB didn't. As long as forage is abundant, RW should be reflect that abundance with high RW. When there is a lot of variation of RW, this is a sign that forage availability is limiting growth.
Culling just on the basis of RW can work against goals. Different fish have different genetic potential for making growth increment. A slow grower by length can attain high RW and yet not have the trophy potential of its peer that put more energy into growing frame. Its important to understand age and length increment potential when culling fish.
I'm with Boondoggle's thoughts that getting a length and weight measurement that can be put in excel for posterity is a good thing. Honestly, I think that is all that is required. I don't believe waiting for poor RW as incentive to cull fish is a good management method. I think its too late and the damage is already done. To effectively manage maximum future growth (later evidenced by high RW) one must be proactive and that could require culling fish of good RW.
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
I am using this (no bass in the pond yet) but it will allow me to refer back to the fish when they were initially stocked at watch what happens to them over time. There's a tab for LMB, BG/RES, YP (my sportfish in the pond). Also created tabs for feeding, stocking, and general pond observations.
My thoughts on this are when asking you guys for help, info or opinions I would be able to provide pretty solid data as to what I did, what I am seeing or have seen recently.
I have to input (3) lines on each sheet for it to work. Length and Weight of sample fish and then find the corresponding "standard weight" for that length. RW calc populates from there. Not nearly as fancy as the one Bob shared with graphing.
Assuming your length column is "B" the following formula in the second cell of the RW Average Column it would compute the SW so you wouldn't have to reference the chart and hand enter the standard weight each time.
=.0003488 * B2^3.163
The RWFish appears to compute from a formula in excel so you would be good to go..
It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers
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