103


 Because the Gambusia population was made up of

 individuals varying in size from 2 mm to 39 mm and the size

 distribution showed a progression from summer to winter of

 smaller to larger individuals predominating, a different

 respiration rate was calculated for each size class and the

 different rates were apportioned among the population

 according to the size frequency distribution on each

 collecting date. Group oxygen consumption on a per gram

 fish basis was then calculated by dividing total group

 respiration by total group weight for each date. The

 equation was:

 0.339 Nx(W0.568)
 R N (22)


where N is the number of fish in each size class, W is
 x w
 the individual wet weight of the size class, and Wd is the

 individual dry weight of the size class.

 Individual weights were estimated for each length

class using the equation:



 Wd = a ebx (23)


where Wd is dry weight and x is length. Coefficients were

obtained from regression analysis of specimens from the

collection (n = 37). This figure was multiplied by 4.76 to

obtain the wet weight estimate needed for the von

Bertalanffy equation. The equation was: