Wednesday, October 30, 2013
Grass Carp Length vs Weight Table
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.