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| Introduction | Trophy Bass Proportions | Model Development | Results | Well Known Bass | Conclusions |


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.


Figure 1.


Figure 2.


[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

IGFA 927 Model

Percent Difference from Actual

958 Model

Percent Difference from Actual

Empirical Model

Percent Difference from Actual

Forced Volume Model

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

inches

Estimated Weight

pounds

Estimated Weight Plus 5%, pounds

Perry

32.5

28.5

21.49

22.57

Duclos

29

29

20.17

21.17

Duclos

29

30

20.71

21.75

Duclos

30

29

20.64

21.67

Duclos

30

30

21.20

22.26

 
Copyright © Robert Belloni 1997-2012. All Rights Reserved.
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