MINNEAPOLIS CITY FISHING CLUB
			     September 10, 2000		 


----Flathead Catfish Research----	
  Preliminary Results

Prepared by Jerome Shimizu 

INTRODUCTION:
In a effort to maximize fishing pleasure, we seek to find the ultimate fishing spot which contains
the largest fish. In order to determine the quality of a location we want to know not only the 
average size of fish, and the variation in fish size, but also the average weight at a given length.
We seek locations were the fish are unusually heavy for a given length and project forward. Before
this can be done we begin by creating a model of the typical fish.  This paper focuses specifically
on flathead Catfish, though this approach can be applied to any species.

MODEL:
This study assumes the relationship between a catfish's length and weight is cubic in
nature.  We assume the equation will go through the origin. This makes sense since a
fish of zero length would have a weight of zero pounds.
Then, the functional form would be:

		WEIGHT=k(LENGTH)³ 

	where k is the coefficient we seek to estimate.

ANALYSIS/RESULTS:

. regress weight length3, noc

  Source |       SS       df       MS                  Number of obs =       8
---------+------------------------------               F(  1,     7) =  449.77
   Model |  18857.7542     1  18857.7542               Prob > F      =  0.0000
Residual |  293.495753     7  41.9279647               R-squared     =  0.9847
---------+------------------------------               Adj R-squared =  0.9825
   Total |    19151.25     8  2393.90625               Root MSE      =  6.4752

------------------------------------------------------------------------------
  weight |      Coef.   Std. Err.       t     P>|t|       [95% Conf. Interval]
---------+--------------------------------------------------------------------
 length3 |    .000662   .0000312     21.208   0.000       .0005882    .0007358
------------------------------------------------------------------------------

. sum length weight length3

Variable |     Obs        Mean   Std. Dev.       Min        Max
---------+-----------------------------------------------------
  length |       8       35.25   15.76388          0         50  
  weight |       8     39.3125   31.13902          0         90  
 length3 |       8     62014.5   41861.41          0     125000  




MODEL RESULTS:
			WEIGHT= (1/1511) x (LENGTH)³

CONCULSIONS:
Using the standard functional form of a cube of the length to estimate a Flathead Catfishes weight,
model results found a strong relationship. The R^2 of .98 and the t-value of 21.2 are impressive.  
This is not surprising since a Catfish is really just a 3-Dimensional volume.

FUTURE RESEARCH:
Having data on girth would be beneficial in creating a more flexible model.  This model assumes average
girth. Having a girth variable would allow you to account for unusually heavy fish.  Also, more data
points from varied fishing locations would be beneficial.  The limited number of sample locations in 
this study introduced the potential bias of modeling fish of a specific location, not flathead
catfish in general.  This becomes problematic when the sample location has, for example, fish of unusual 
girth.





©2000 Twin Cities Fishing Club.   All rights reserved.   Catch & Release.