Although the models presented above provide a more accurate estimate for a trophy bass’ weight than models of the past, a larger sample size of bass in the 18 to 20 pound range must be analyzed. Users of these models must understand the deviations from actual weight when applying these models to their catches. Also of interest were the results from the L/G versus Weight Percent Difference study. The reason this is interesting is shown along the L/G line at values between 1.15 and 1.20. Fish that fall within this interval are quite accurately estimated in weight with an under estimate no greater than weight 5%. This was of particular interest to me in this study due to the latest fish that was submitted for a world record. This fish, having an L/G value of 1.16 and using the empirical model, would have been estimated to weigh between 17.94 lbs and 18.83 lbs instead of the 22.5 lbs claimed.
[1] Data for this study were obtained from the Texas Parks and Wildlife Department Share a Lunker Program, The City of San Diego, the California Department of Fish and Game and Mike Long (as certified by the San Diego Parks Dept.). Sixty seven trophy bass, weighing over 14.25 pounds each, were analyzed using their actual weight, length, and girth.
[2] Although, for this particular bass, the outcome is weighted high, this model produced better overall results than the IGFA and 958 Models when all fish were considered.
Model Name
Formula
Maximum Deviation %
Sum of Least Squares
Empirical Model
-17.29/+10.98
85.2
Forced Volume Model
-20.78/+16.02
162.3
958 Model
-27.90/+18.55
187.9
IGFA 927 Model
-23.78/+21.77
208.
Table 1. Three newly developed models compared to the new 927-Model developed by the IGFA.
Confidence Interval
Percent Difference from Actual
90%
-0.9% / +3.3%
-4.2% / +0.1%
-1.4% / +1.4%
-3.7% / +0.3%
95%
-1.3% / +3.7%
-4.6% / +0.5%
-1.7% / +1.6%
-4.1% / +0.6%
99%
-2.1% / +4.5%
-5.5% / +1.3%
-2.2% / +2.2%
-4.9% / +1.4
Table 2. Confidence Intervals for models with range of mass percent deviation from actual weight.
Name
Length
inches
Girth
Estimated Weight
pounds
Estimated Weight Plus 5%, pounds
Perry
32.5
28.5
21.49
22.57
Duclos
29
20.17
21.17
30
20.71
21.75
20.64
21.67
21.20
22.26