One of our Iowa DNR Fisheries Biologists sent me a study (by others) that had been completed in 2009 on Asiatic Carp in the Missouri River. The study's authors were Wanner and Klumb.
Part of the result of the study was coming up with Length vs Weight tables for Bighead Carp, Silver Carp, and Grass Carp. Each species was dealt with separately.
The Grass Carp in the Missouri River deal with current and a general lack of their preferred vegetative foods. So, I strongly suspect the condition of these river fish is significantly less than a pond or lake
fish with practically unlimited food supply. I know the Grass Carp I've caught have usually been very fat.
But anyway, having some guideline by which to estimate these fishes' weights is better than none, and its perfect if you are actually catching Missouri River (or probably any river) Grass Carp.
Accordingly, I took one of the equations from the study and put it in an Excel Spreadsheet to develop the table. The formula I used was:
Log(weight in grams)= 2.87 x (Log length in mm) - 4.59
I converted the formula for input of fish length in inches, and an output of weight in pounds.
Below is an example table. At the top of the image, I show what the formula looks like in the Excel spreadsheet, so you can make one for yourself if you wish. In that formula, "A23" is just the cell callout for the cell where you've entered the fish length in inches. In your table, just change that callout to the appropriate cell number. Once you done this for one line, you can copy the formula down in subsequent cells and it should update that cell callout automatically, if you know what I mean.
Below is the result of another study I found, this one by Morrow and Kirk on Grass Carp in Lake Guntersville, Alabama. These length vs weights I feel are probably more like what I might expect from my local pond fish. Below is the image for those results, along with those from the Missouri River study, and also shows the formula I used as it was entered into the Excel spreadsheet.
The formula used is:
Weight (grams) = (length in mm)^3.14 x .00000519
Of course, once again in my table, I've converted for accepting lengths in inches and giving results in pounds.
That is something else. I could only dream about landing a 30.5 lbs. Grass Carp. Now you go and make spreadsheets and have "insider" info. Man, this is great stuff.
ReplyDeleteHa! I haven't caught a 30.5 lb Grass Carp yet! The one this year was 30.5", which according to this info, was probably in the 13-pound range...although it sure looks a lot bigger!
ReplyDeleteGotcha.
DeleteI have since caught a bigger one! 41.5" long, calculated weight of approximately 35 pounds. BEAST! Caught while flyfishing for bluegills with a #10 gray boa yarn leech. It ate it!
Deleteoh...and with 8 lb tippet on a 5wt rod!
Deletehi guys
ReplyDeletei recently caught an 80cm grass carp on fly. nowhere can it tell me its weight. it was 80cm length and 24cm deep. can anyone help
Kind of depends on where you caught it. A river grass carp of that length would be around 12 pounds (4.54 kg). A lake grass carp of that length would be around 15 pounds (5.67 kg).
DeleteI recently caught a grass carp in Croatia from a lake it weighed 72lb and guessed it to be over 4 feet and under 5 feet long
ReplyDeleteAwesome! That fits this equation nicely. According to this, a 72 lb lake Grass Carp should measure 4 feet 4 inches...or 52 inches long. Congratulations on your big fish!
DeleteToday I caught a 5 ft grass carp. It maxed out my scale at 50 pounds. I’m guessing it was at least 80 pounds
ReplyDeleteWow! Congrats! That's a monster Grass Carp for sure! Its impossible to know how accurate the equations/formulas are when you get to extreme sizes....but I plugged 60" into my spreadsheet, and it suggested a weight of 113 lbs! River vs Lake Fish, and how fat it is can make a pretty big weight difference for fish of the same length.... but there you go!
DeleteI recently caught a lake grass carp
ReplyDeleteIt was extremely fat
Measurements were 45” length, 13” height ,and 8” thick
Any ideas on approximate weight?
Based on the equations for lake grass carp, the suggested weight for a 45" long Grass Carp would be 45.8 lbs. That already takes into account a fat healthy fish like the lake ones tend to be...but that doesn't mean yours wouldn't weigh even more. I would say you could probably safely and conservatively estimate it at a MINIMUM of 46 lbs. Nice fish!
Delete